1050显卡 8G内存 可以玩方舟生存进化烧显卡么
点击联系发帖人
时间：2017-09-16 21:56
2012年3月 Java大版内专家分月排行榜第三
本帖子已过去太久远了，不再提供回复功能。> 问题详情
求解Java程序设计编写一个日期对应的星期几程序
悬赏：0&答案豆
提问人：匿名网友
发布时间：
求解Java程序设计编写一个日期对应的星期几程序
论文写作技巧
我有更好的答案
请先输入下方的验证码查看最佳答案
图形验证：
验证码提交中……PathMeasure之迷径追踪
Path，不论是在自定义View还是动画，都占有举足轻重的地位。绘制Path，可以通过提供的API，或者是贝塞尔曲线、数学函数、图形组合等等方式，而要获取Path上每一个构成点的坐标，一般需要知道Path的函数方法，例如求解贝塞尔曲线上的点的De
Casteljau算法，但对于一般的Path来说，是很难通过简单的函数方法来进行计算的，那么，如何来定位任意一个给定Path的任意一个点的坐标呢？
Android SDK提供了一个非常有用的API来帮助开发者实现这样一个Path路径点的坐标追踪，这个类就是PathMeasure，它可以认为是一个Path的坐标计算器。
PathMeasure类似一个计算器，对它进行初始化只需要new一个PathMeasure对象即可：
&code class=&hljs fix has-numbering& style=&display: padding: 0 color: box-sizing: border- font-family: 'Source Code Pro',font-size: white-space: border-radius: 0 word-wrap: background:&&&span class=&hljs-attribute& style=&box-sizing: border-&&PathMeasure pathMeasure &/span&=&span class=&hljs-string& style=&color: rgb(0, 136, 0); box-sizing: border-&& new PathMeasure();&/span&&/code&&ul class=&pre-numbering& style=&box-sizing: border- position: width: 50 top: 0 left: 0 margin: 0 padding: 6px 0px 40 border-right-width: 1 border-right-style: border-right-color: rgb(221, 221, 221); list-style: text-align: background-color: rgb(238, 238, 238);&&&li style=&box-sizing: border- padding: 0px 5&&1&/li&&/ul&&ul class=&pre-numbering& style=&box-sizing: border- position: width: 50 top: 0 left: 0 margin: 0 padding: 6px 0px 40 border-right-width: 1 border-right-style: border-right-color: rgb(221, 221, 221); list-style: text-align: background-color: rgb(238, 238, 238);&&&li style=&box-sizing: border- padding: 0px 5&&1&/li&&/ul&
初始化PathMeasure后，可以通过PathMeasure.setPath()的方式来将Path和PathMeasure进行绑定，例如：
&code class=&hljs bash has-numbering& style=&display: padding: 0 color: box-sizing: border- font-family: 'Source Code Pro',font-size: white-space: border-radius: 0 word-wrap: background:&&pathMeasure.setPath(path, &span class=&hljs-literal& style=&color: rgb(0, 102, 102); box-sizing: border-&&true&/span&);&/code&&ul class=&pre-numbering& style=&box-sizing: border- position: width: 50 top: 0 left: 0 margin: 0 padding: 6px 0px 40 border-right-width: 1 border-right-style: border-right-color: rgb(221, 221, 221); list-style: text-align: background-color: rgb(238, 238, 238);&&&li style=&box-sizing: border- padding: 0px 5&&1&/li&&/ul&&ul class=&pre-numbering& style=&box-sizing: border- position: width: 50 top: 0 left: 0 margin: 0 padding: 6px 0px 40 border-right-width: 1 border-right-style: border-right-color: rgb(221, 221, 221); list-style: text-align: background-color: rgb(238, 238, 238);&&&li style=&box-sizing: border- padding: 0px 5&&1&/li&&/ul&
当然，你也可以直接使用PathMeasure的有参构造方法来进行初始化：
&code class=&hljs java has-numbering& style=&display: padding: 0 color: box-sizing: border- font-family: 'Source Code Pro',font-size: white-space: border-radius: 0 word-wrap: background:&&PathMeasure (Path path, &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&boolean&/span& forceClosed)&/code&&ul class=&pre-numbering& style=&box-sizing: border- position: width: 50 top: 0 left: 0 margin: 0 padding: 6px 0px 40 border-right-width: 1 border-right-style: border-right-color: rgb(221, 221, 221); list-style: text-align: background-color: rgb(238, 238, 238);&&&li style=&box-sizing: border- padding: 0px 5&&1&/li&&/ul&&ul class=&pre-numbering& style=&box-sizing: border- position: width: 50 top: 0 left: 0 margin: 0 padding: 6px 0px 40 border-right-width: 1 border-right-style: border-right-color: rgb(221, 221, 221); list-style: text-align: background-color: rgb(238, 238, 238);&&&li style=&box-sizing: border- padding: 0px 5&&1&/li&&/ul&
这里最不容易理解的就是第二个boolean参数forceClosed。
forceClosed参数
这个参数——forceClosed，简单的说，就是Path最终是否需要闭合，如果为True的话，则不管关联的Path是否是闭合的，都会被闭合。
但是这个参数对Path和PathMeasure的影响是需要解释下的：
forceClosed参数对绑定的Path不会产生任何影响，例如一个折线段的Path，本身是没有闭合的，forceClosed设置为True的时候，PathMeasure计算的Path是闭合的，但Path本身绘制出来是不会闭合的。forceClosed参数对PathMeasure的测量结果有影响，还是例如前面说的一个折线段的Path，本身没有闭合，forceClosed设置为True，PathMeasure的计算就会包含最后一段闭合的路径，与原来的Path不同。
PathMeasure的API非常容易理解，几乎都是望文生义。
PathMeasure.getLength()的使用非常广泛，其作用就是获取计算的路径长度。
getSegment
&code class=&hljs java has-numbering& style=&display: padding: 0 color: box-sizing: border- font-family: 'Source Code Pro',font-size: white-space: border-radius: 0 word-wrap: background:&&&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&boolean&/span& getSegment (&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&float&/span& startD, &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&float&/span& stopD, Path dst, &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&boolean&/span& startWithMoveTo)&/code&&ul class=&pre-numbering& style=&box-sizing: border- position: width: 50 top: 0 left: 0 margin: 0 padding: 6px 0px 40 border-right-width: 1 border-right-style: border-right-color: rgb(221, 221, 221); list-style: text-align: background-color: rgb(238, 238, 238);&&&li style=&box-sizing: border- padding: 0px 5&&1&/li&&/ul&&ul class=&pre-numbering& style=&box-sizing: border- position: width: 50 top: 0 left: 0 margin: 0 padding: 6px 0px 40 border-right-width: 1 border-right-style: border-right-color: rgb(221, 221, 221); list-style: text-align: background-color: rgb(238, 238, 238);&&&li style=&box-sizing: border- padding: 0px 5&&1&/li&&/ul&
这个API用于截取整个Path的片段，通过参数startD和stopD来控制截取的长度，并将截取的Path保存到dst中，最后一个参数startWithMoveTo表示起始点是否使用moveTo方法，通常为True，保证每次截取的Path片段都是正常的、完整的。
如果startWithMoveTo设置为false，通常是和dst一起使用，因为dst中保存的Path是被不断添加的，而不是每次被覆盖，设置为false，则新增的片段会从上一次Path终点开始计算，这样可以保存截取的Path片段数组连续起来。
nextContour
nextContour()方法用的比较少，比较大部分情况下都只会有一个Path而不是多个，毕竟这样会增加Path的复杂度，但是如果真有一个Path，包含了多个Path，那么通过nextContour这个方法，就可以进行切换，同时，默认的API，例如getLength，获取的也是当前的这段Path所对应的长度，而不是所有的Path的长度，同时，nextContour获取Path的顺序，与Path的添加顺序是相同的。
&code class=&hljs glsl has-numbering& style=&display: padding: 0 color: box-sizing: border- font-family: 'Source Code Pro',font-size: white-space: border-radius: 0 word-wrap: background:&&boolean getPosTan (&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&float&/span& &span class=&hljs-built_in& style=&color: rgb(102, 0, 102); box-sizing: border-&&distance&/span&, &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&float&/span&[] pos, &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&float&/span&[] &span class=&hljs-built_in& style=&color: rgb(102, 0, 102); box-sizing: border-&&tan&/span&)&/code&&ul class=&pre-numbering& style=&box-sizing: border- position: width: 50 top: 0 left: 0 margin: 0 padding: 6px 0px 40 border-right-width: 1 border-right-style: border-right-color: rgb(221, 221, 221); list-style: text-align: background-color: rgb(238, 238, 238);&&&li style=&box-sizing: border- padding: 0px 5&&1&/li&&/ul&&ul class=&pre-numbering& style=&box-sizing: border- position: width: 50 top: 0 left: 0 margin: 0 padding: 6px 0px 40 border-right-width: 1 border-right-style: border-right-color: rgb(221, 221, 221); list-style: text-align: background-color: rgb(238, 238, 238);&&&li style=&box-sizing: border- padding: 0px 5&&1&/li&&/ul&
这个API用于获取路径上某点的坐标及其切线的坐标，这个API非常强大，但是比较难理解，后面会结合例子来讲解。
简单的说，就是通过指定distance（0
硬件加速的Bug
由于硬件加速的问题，PathMeasure中的getSegment在讲Path添加到dst数组中时会被导致一些错误，需要通过mDst.lineTo(0,0)来避免这样一个Bug。
路径绘制是PathMeasure最常用的功能，其原理就是通过getSegment来不断截取Path片段，从而不断绘制完整的路径，效果如图所示：
代码如下所示：
&code class=&hljs java has-numbering& style=&display: padding: 0 color: box-sizing: border- font-family: 'Source Code Pro',font-size: white-space: border-radius: 0 word-wrap: background:&&&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&package&/span& .pathart.
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&import&/span& android.animation.ValueA
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&import&/span& android.content.C
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&import&/span& android.graphics.C
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&import&/span& android.graphics.P
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&import&/span& android.graphics.P
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&import&/span& android.graphics.PathM
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&import&/span& android.util.AttributeS
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&import&/span& android.view.V
&span class=&hljs-javadoc& style=&color: rgb(136, 0, 0); box-sizing: border-&&/**
* 路径动画 PathMeasure
* Created by xuyisheng on 16/7/15.
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&public&/span& &span class=&hljs-class& style=&box-sizing: border-&&&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&class&/span& &span class=&hljs-title& style=&box-sizing: border- color: rgb(102, 0, 102);&&PathPainter&/span& &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&extends&/span& &span class=&hljs-title& style=&box-sizing: border- color: rgb(102, 0, 102);&&View&/span& {&/span&
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&private&/span& Path mP
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&private&/span& Paint mP
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&private&/span& PathMeasure mPathM
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&private&/span& &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&float&/span& mAnimatorV
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&private&/span& Path mD
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&private&/span& &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&float&/span& mL
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&public&/span& &span class=&hljs-title& style=&box-sizing: border-&&PathPainter&/span&(Context context) {
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&super&/span&(context);
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&public&/span& &span class=&hljs-title& style=&box-sizing: border-&&PathPainter&/span&(Context context, AttributeSet attrs) {
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&super&/span&(context, attrs);
mPathMeasure = &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&new&/span& PathMeasure();
mPaint = &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&new&/span& Paint(Paint.ANTI_ALIAS_FLAG);
mPaint.setStyle(Paint.Style.STROKE);
mPaint.setStrokeWidth(&span class=&hljs-number& style=&color: rgb(0, 102, 102); box-sizing: border-&&5&/span&);
mPath = &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&new&/span& Path();
mPath.addCircle(&span class=&hljs-number& style=&color: rgb(0, 102, 102); box-sizing: border-&&400&/span&, &span class=&hljs-number& style=&color: rgb(0, 102, 102); box-sizing: border-&&400&/span&, &span class=&hljs-number& style=&color: rgb(0, 102, 102); box-sizing: border-&&100&/span&, Path.Direction.CW);
mPathMeasure.setPath(mPath, &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&true&/span&);
mLength = mPathMeasure.getLength();
mDst = &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&new&/span& Path();
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&final&/span& ValueAnimator valueAnimator = ValueAnimator.ofFloat(&span class=&hljs-number& style=&color: rgb(0, 102, 102); box-sizing: border-&&0&/span&, &span class=&hljs-number& style=&color: rgb(0, 102, 102); box-sizing: border-&&1&/span&);
valueAnimator.addUpdateListener(&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&new&/span& ValueAnimator.AnimatorUpdateListener() {
&span class=&hljs-annotation& style=&color: rgb(155, 133, 157); box-sizing: border-&&@Override&/span&
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&public&/span& &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&void&/span& &span class=&hljs-title& style=&box-sizing: border-&&onAnimationUpdate&/span&(ValueAnimator valueAnimator) {
mAnimatorValue = (&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&float&/span&) valueAnimator.getAnimatedValue();
invalidate();
valueAnimator.setDuration(&span class=&hljs-number& style=&color: rgb(0, 102, 102); box-sizing: border-&&2000&/span&);
valueAnimator.setRepeatCount(ValueAnimator.INFINITE);
valueAnimator.start();
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&public&/span& &span class=&hljs-title& style=&box-sizing: border-&&PathPainter&/span&(Context context, AttributeSet attrs, &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&int&/span& defStyleAttr) {
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&super&/span&(context, attrs, defStyleAttr);
&span class=&hljs-annotation& style=&color: rgb(155, 133, 157); box-sizing: border-&&@Override&/span&
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&protected&/span& &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&void&/span& &span class=&hljs-title& style=&box-sizing: border-&&onDraw&/span&(Canvas canvas) {
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&super&/span&.onDraw(canvas);
mDst.reset();
&span class=&hljs-comment& style=&color: rgb(136, 0, 0); box-sizing: border-&&// 硬件加速的BUG&/span&
mDst.lineTo(&span class=&hljs-number& style=&color: rgb(0, 102, 102); box-sizing: border-&&0&/span&,&span class=&hljs-number& style=&color: rgb(0, 102, 102); box-sizing: border-&&0&/span&);
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&float&/span& stop = mLength * mAnimatorV
mPathMeasure.getSegment(&span class=&hljs-number& style=&color: rgb(0, 102, 102); box-sizing: border-&&0&/span&, stop, mDst, &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&true&/span&);
canvas.drawPath(mDst, mPaint);
&/code&&p&&code class=&hljs java has-numbering& style=&display: padding: 0 color: box-sizing: border- font-family: 'Source Code Pro',font-size: white-space: border-radius: 0 word-wrap: background:&&
}&/code&&code class=&hljs java has-numbering& style=&display: padding: 0 color: box-sizing: border- font-family: 'Source Code Pro',font-size: white-space: border-radius: 0 word-wrap: background:&&
&/code&&code class=&hljs java has-numbering& style=&display: padding: 0 color: box-sizing: border- font-family: 'Source Code Pro',font-size: white-space: border-radius: 0 word-wrap: background:&&
&/code&&code class=&hljs java has-numbering& style=&display: padding: 0 color: box-sizing: border- font-family: 'Source Code Pro',font-size: white-space: border-radius: 0 word-wrap: background:&&&/code&&/p&&p style=&margin-top: 0 margin-bottom: 1.1 padding-top: 0 padding-bottom: 0 box-sizing: border- color: rgb(85, 85, 85); font-family: 'microsoft yahei'; font-size: 14 line-height: 35&&通过这种方式，只需要做一点点小的修改，就可以完成一个比较有意思的loading图，效果如下所示：&/p&&p style=&margin-top: 0 margin-bottom: 1.1 padding-top: 0 padding-bottom: 0 box-sizing: border- color: rgb(85, 85, 85); font-family: 'microsoft yahei'; font-size: 14 line-height: 35&&&img src=&http://img.blog.csdn.net/13306& alt=&这里写图片描述& title=&& style=&border: box-sizing: border- max-width: 602 height:& /&&/p&&p style=&margin-top: 0 margin-bottom: 1.1 padding-top: 0 padding-bottom: 0 box-sizing: border- color: rgb(85, 85, 85); font-family: 'microsoft yahei'; font-size: 14 line-height: 35&&我们只需要修改下起始值的数字即可，关键代码如下：&/p&&pre class=&prettyprint& name=&code& style=&white-space: word-wrap: break- box-sizing: border- position: overflow-y: overflow-x: margin-top: 0 margin-bottom: 1.1 font-family: 'Source Code Pro', padding: 5px 5px 5px 60 font-size: 14 line-height: 1.45; word-break: break- color: rgb(51, 51, 51); border: 1px solid rgba(128, 128, 128, 0.0745098); border-radius: 0 background-color: rgba(128, 128, 128, 0.0470588);&&&code class=&hljs java has-numbering& style=&display: padding: 0 color: box-sizing: border- font-family: 'Source Code Pro',font-size: white-space: border-radius: 0 word-wrap: background:&&&span class=&hljs-annotation& style=&color: rgb(155, 133, 157); box-sizing: border-&&@Override&/span&
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&protected&/span& &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&void&/span& &span class=&hljs-title& style=&box-sizing: border-&&onDraw&/span&(Canvas canvas) {
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&super&/span&.onDraw(canvas);
mDst.reset();
&span class=&hljs-comment& style=&color: rgb(136, 0, 0); box-sizing: border-&&// 硬件加速的BUG&/span&
mDst.lineTo(&span class=&hljs-number& style=&color: rgb(0, 102, 102); box-sizing: border-&&0&/span&,&span class=&hljs-number& style=&color: rgb(0, 102, 102); box-sizing: border-&&0&/span&);
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&float&/span& stop = mLength * mAnimatorV
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&float&/span& start = (&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&float&/span&) (stop - ((&span class=&hljs-number& style=&color: rgb(0, 102, 102); box-sizing: border-&&0.5&/span& - Math.abs(mAnimatorValue - &span class=&hljs-number& style=&color: rgb(0, 102, 102); box-sizing: border-&&0.5&/span&)) * mLength));
mPathMeasure.getSegment(start, stop, mDst, &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&true&/span&);
canvas.drawPath(mDst, mPaint);
}&/code&&ul class=&pre-numbering& style=&box-sizing: border- position: width: 50 top: 0 left: 0 margin: 0 padding: 6px 0px 40 border-right-width: 1 border-right-style: border-right-color: rgb(221, 221, 221); list-style: text-align: background-color: rgb(238, 238, 238);&&&li style=&box-sizing: border- padding: 0px 5&&1&/li&&li style=&box-sizing: border- padding: 0px 5&&2&/li&&li style=&box-sizing: border- padding: 0px 5&&3&/li&&li style=&box-sizing: border- padding: 0px 5&&4&/li&&li style=&box-sizing: border- padding: 0px 5&&5&/li&&li style=&box-sizing: border- padding: 0px 5&&6&/li&&li style=&box-sizing: border- padding: 0px 5&&7&/li&&li style=&box-sizing: border- padding: 0px 5&&8&/li&&li style=&box-sizing: border- padding: 0px 5&&9&/li&&li style=&box-sizing: border- padding: 0px 5&&10&/li&&li style=&box-sizing: border- padding: 0px 5&&11&/li&&/ul&&ul class=&pre-numbering& style=&box-sizing: border- position: width: 50 top: 0 left: 0 margin: 0 padding: 6px 0px 40 border-right-width: 1 border-right-style: border-right-color: rgb(221, 221, 221); list-style: text-align: background-color: rgb(238, 238, 238);&&&li style=&box-sizing: border- padding: 0px 5&&1&/li&&li style=&box-sizing: border- padding: 0px 5&&2&/li&&li style=&box-sizing: border- padding: 0px 5&&3&/li&&li style=&box-sizing: border- padding: 0px 5&&4&/li&&li style=&box-sizing: border- padding: 0px 5&&5&/li&&li style=&box-sizing: border- padding: 0px 5&&6&/li&&li style=&box-sizing: border- padding: 0px 5&&7&/li&&li style=&box-sizing: border- padding: 0px 5&&8&/li&&li style=&box-sizing: border- padding: 0px 5&&9&/li&&li style=&box-sizing: border- padding: 0px 5&&10&/li&&li style=&box-sizing: border- padding: 0px 5&&11&/li&&/ul&
路径绘制——另辟蹊径
关于路径绘制，View的始祖Romain Guy曾经有一篇文章讲解了一个很使用的技巧，地址如下所示：
Romain Guy使用DashPathEffect来实现了路径绘制。
&code class=&hljs cs has-numbering& style=&display: padding: 0 color: box-sizing: border- font-family: 'Source Code Pro',font-size: white-space: border-radius: 0 word-wrap: background:&&DashPathEffect(&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&float&/span&[] intervals, &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&float&/span& phase)&/code&&ul class=&pre-numbering& style=&box-sizing: border- position: width: 50 top: 0 left: 0 margin: 0 padding: 6px 0px 40 border-right-width: 1 border-right-style: border-right-color: rgb(221, 221, 221); list-style: text-align: background-color: rgb(238, 238, 238);&&&li style=&box-sizing: border- padding: 0px 5&&1&/li&&/ul&&ul class=&pre-numbering& style=&box-sizing: border- position: width: 50 top: 0 left: 0 margin: 0 padding: 6px 0px 40 border-right-width: 1 border-right-style: border-right-color: rgb(221, 221, 221); list-style: text-align: background-color: rgb(238, 238, 238);&&&li style=&box-sizing: border- padding: 0px 5&&1&/li&&/ul&
DashPathEffect传入了一个intervals数组，用来控制实线和虚线的数组的显示，那么当实线和虚线都是整个路径的长度时，整个路径就只显示实线或者虚线了，这时候通过第二个参数phase来控制起始偏移量，就可以完成整个路径的绘制了，这的确是一个非常trick而且有效的方式，效果如图所示：
代码如下所示：
&code class=&hljs java has-numbering& style=&display: padding: 0 color: box-sizing: border- font-family: 'Source Code Pro',font-size: white-space: border-radius: 0 word-wrap: background:&&&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&package&/span& .pathart.
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&import&/span& android.animation.ValueA
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&import&/span& android.content.C
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&import&/span& android.graphics.C
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&import&/span& android.graphics.C
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&import&/span& android.graphics.DashPathE
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&import&/span& android.graphics.P
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&import&/span& android.graphics.P
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&import&/span& android.graphics.PathE
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&import&/span& android.graphics.PathM
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&import&/span& android.util.AttributeS
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&import&/span& android.view.V
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&import&/span& android.view.animation.AccelerateDecelerateI
&span class=&hljs-javadoc& style=&color: rgb(136, 0, 0); box-sizing: border-&&/**
* 路径绘制——DashPathEffect
* Created by xuyisheng on 16/7/15.
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&public&/span& &span class=&hljs-class& style=&box-sizing: border-&&&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&class&/span& &span class=&hljs-title& style=&box-sizing: border- color: rgb(102, 0, 102);&&PathPainterEffect&/span& &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&extends&/span& &span class=&hljs-title& style=&box-sizing: border- color: rgb(102, 0, 102);&&View&/span& &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&implements&/span& &span class=&hljs-title& style=&box-sizing: border- color: rgb(102, 0, 102);&&View&/span&.&span class=&hljs-title& style=&box-sizing: border- color: rgb(102, 0, 102);&&OnClickListener&/span&{&/span&
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&private&/span& Paint mP
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&private&/span& Path mP
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&private&/span& PathMeasure mPathM
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&private&/span& PathEffect mE
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&private&/span& &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&float&/span& fraction = &span class=&hljs-number& style=&color: rgb(0, 102, 102); box-sizing: border-&&0&/span&;
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&private&/span& ValueAnimator mA
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&public&/span& &span class=&hljs-title& style=&box-sizing: border-&&PathPainterEffect&/span&(Context context) {
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&super&/span&(context);
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&public&/span& &span class=&hljs-title& style=&box-sizing: border-&&PathPainterEffect&/span&(Context context, AttributeSet attrs) {
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&super&/span&(context, attrs);
mPath = &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&new&/span& Path();
mPath.reset();
mPath.moveTo(&span class=&hljs-number& style=&color: rgb(0, 102, 102); box-sizing: border-&&100&/span&, &span class=&hljs-number& style=&color: rgb(0, 102, 102); box-sizing: border-&&100&/span&);
mPath.lineTo(&span class=&hljs-number& style=&color: rgb(0, 102, 102); box-sizing: border-&&100&/span&, &span class=&hljs-number& style=&color: rgb(0, 102, 102); box-sizing: border-&&500&/span&);
mPath.lineTo(&span class=&hljs-number& style=&color: rgb(0, 102, 102); box-sizing: border-&&400&/span&, &span class=&hljs-number& style=&color: rgb(0, 102, 102); box-sizing: border-&&300&/span&);
mPath.close();
mPaint = &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&new&/span& Paint();
mPaint.setColor(Color.BLACK);
mPaint.setStyle(Paint.Style.STROKE);
mPaint.setStrokeWidth(&span class=&hljs-number& style=&color: rgb(0, 102, 102); box-sizing: border-&&5&/span&);
mPathMeasure = &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&new&/span& PathMeasure(mPath, &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&false&/span&);
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&final&/span& &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&float&/span& length = mPathMeasure.getLength();
mAnimator = ValueAnimator.ofFloat(&span class=&hljs-number& style=&color: rgb(0, 102, 102); box-sizing: border-&&1&/span&, &span class=&hljs-number& style=&color: rgb(0, 102, 102); box-sizing: border-&&0&/span&);
mAnimator.setInterpolator(&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&new&/span& AccelerateDecelerateInterpolator());
mAnimator.setDuration(&span class=&hljs-number& style=&color: rgb(0, 102, 102); box-sizing: border-&&2000&/span&);
mAnimator.addUpdateListener(&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&new&/span& ValueAnimator.AnimatorUpdateListener() {
&span class=&hljs-annotation& style=&color: rgb(155, 133, 157); box-sizing: border-&&@Override&/span&
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&public&/span& &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&void&/span& &span class=&hljs-title& style=&box-sizing: border-&&onAnimationUpdate&/span&(ValueAnimator valueAnimator) {
fraction = (&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&float&/span&) valueAnimator.getAnimatedValue();
mEffect = &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&new&/span& DashPathEffect(&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&new&/span& &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&float&/span&[]{length, length}, fraction * length);
mPaint.setPathEffect(mEffect);
invalidate();
setOnClickListener(&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&this&/span&);
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&public&/span& &span class=&hljs-title& style=&box-sizing: border-&&PathPainterEffect&/span&(Context context, AttributeSet attrs, &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&int&/span& defStyleAttr) {
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&super&/span&(context, attrs, defStyleAttr);
&span class=&hljs-annotation& style=&color: rgb(155, 133, 157); box-sizing: border-&&@Override&/span&
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&protected&/span& &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&void&/span& &span class=&hljs-title& style=&box-sizing: border-&&onDraw&/span&(Canvas canvas) {
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&super&/span&.onDraw(canvas);
canvas.drawPath(mPath, mPaint);
&span class=&hljs-annotation& style=&color: rgb(155, 133, 157); box-sizing: border-&&@Override&/span&
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&public&/span& &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&void&/span& &span class=&hljs-title& style=&box-sizing: border-&&onClick&/span&(View view) {
mAnimator.start();
&/code&&ul class=&pre-numbering& style=&box-sizing: border- position: width: 50 top: 0 left: 0 margin: 0 padding: 6px 0px 40 border-right-width: 1 border-right-style: border-right-color: rgb(221, 221, 221); list-style: text-align: background-color: rgb(238, 238, 238);&&&li style=&box-sizing: border- padding: 0px 5&&1&/li&&li style=&box-sizing: border- padding: 0px 5&&2&/li&&li style=&box-sizing: border- padding: 0px 5&&3&/li&&li style=&box-sizing: border- padding: 0px 5&&4&/li&&li style=&box-sizing: border- padding: 0px 5&&5&/li&&li style=&box-sizing: border- padding: 0px 5&&6&/li&&li style=&box-sizing: border- padding: 0px 5&&7&/li&&li style=&box-sizing: border- padding: 0px 5&&8&/li&&li style=&box-sizing: border- padding: 0px 5&&9&/li&&li style=&box-sizing: border- padding: 0px 5&&10&/li&&li style=&box-sizing: border- padding: 0px 5&&11&/li&&li style=&box-sizing: border- padding: 0px 5&&12&/li&&li style=&box-sizing: border- padding: 0px 5&&13&/li&&li style=&box-sizing: border- padding: 0px 5&&14&/li&&li style=&box-sizing: border- padding: 0px 5&&15&/li&&li style=&box-sizing: border- padding: 0px 5&&16&/li&&li style=&box-sizing: border- padding: 0px 5&&17&/li&&li style=&box-sizing: border- padding: 0px 5&&18&/li&&li style=&box-sizing: border- padding: 0px 5&&19&/li&&li style=&box-sizing: border- padding: 0px 5&&20&/li&&li style=&box-sizing: border- padding: 0px 5&&21&/li&&li style=&box-sizing: border- padding: 0px 5&&22&/li&&li style=&box-sizing: border- padding: 0px 5&&23&/li&&li style=&box-sizing: border- padding: 0px 5&&24&/li&&li style=&box-sizing: border- padding: 0px 5&&25&/li&&li style=&box-sizing: border- padding: 0px 5&&26&/li&&li style=&box-sizing: border- padding: 0px 5&&27&/li&&li style=&box-sizing: border- padding: 0px 5&&28&/li&&li style=&box-sizing: border- padding: 0px 5&&29&/li&&li style=&box-sizing: border- padding: 0px 5&&30&/li&&li style=&box-sizing: border- padding: 0px 5&&31&/li&&li style=&box-sizing: border- padding: 0px 5&&32&/li&&li style=&box-sizing: border- padding: 0px 5&&33&/li&&li style=&box-sizing: border- padding: 0px 5&&34&/li&&li style=&box-sizing: border- padding: 0px 5&&35&/li&&li style=&box-sizing: border- padding: 0px 5&&36&/li&&li style=&box-sizing: border- padding: 0px 5&&37&/li&&li style=&box-sizing: border- padding: 0px 5&&38&/li&&li style=&box-sizing: border- padding: 0px 5&&39&/li&&li style=&box-sizing: border- padding: 0px 5&&40&/li&&li style=&box-sizing: border- padding: 0px 5&&41&/li&&li style=&box-sizing: border- padding: 0px 5&&42&/li&&li style=&box-sizing: border- padding: 0px 5&&43&/li&&li style=&box-sizing: border- padding: 0px 5&&44&/li&&li style=&box-sizing: border- padding: 0px 5&&45&/li&&li style=&box-sizing: border- padding: 0px 5&&46&/li&&li style=&box-sizing: border- padding: 0px 5&&47&/li&&li style=&box-sizing: border- padding: 0px 5&&48&/li&&li style=&box-sizing: border- padding: 0px 5&&49&/li&&li style=&box-sizing: border- padding: 0px 5&&50&/li&&li style=&box-sizing: border- padding: 0px 5&&51&/li&&li style=&box-sizing: border- padding: 0px 5&&52&/li&&li style=&box-sizing: border- padding: 0px 5&&53&/li&&li style=&box-sizing: border- padding: 0px 5&&54&/li&&li style=&box-sizing: border- padding: 0px 5&&55&/li&&li style=&box-sizing: border- padding: 0px 5&&56&/li&&li style=&box-sizing: border- padding: 0px 5&&57&/li&&li style=&box-sizing: border- padding: 0px 5&&58&/li&&li style=&box-sizing: border- padding: 0px 5&&59&/li&&li style=&box-sizing: border- padding: 0px 5&&60&/li&&li style=&box-sizing: border- padding: 0px 5&&61&/li&&li style=&box-sizing: border- padding: 0px 5&&62&/li&&li style=&box-sizing: border- padding: 0px 5&&63&/li&&li style=&box-sizing: border- padding: 0px 5&&64&/li&&li style=&box-sizing: border- padding: 0px 5&&65&/li&&li style=&box-sizing: border- padding: 0px 5&&66&/li&&li style=&box-sizing: border- padding: 0px 5&&67&/li&&li style=&box-sizing: border- padding: 0px 5&&68&/li&&li style=&box-sizing: border- padding: 0px 5&&69&/li&&li style=&box-sizing: border- padding: 0px 5&&70&/li&&li style=&box-sizing: border- padding: 0px 5&&71&/li&&li style=&box-sizing: border- padding: 0px 5&&72&/li&&li style=&box-sizing: border- padding: 0px 5&&73&/li&&li style=&box-sizing: border- padding: 0px 5&&74&/li&&li style=&box-sizing: border- padding: 0px 5&&75&/li&&li style=&box-sizing: border- padding: 0px 5&&76&/li&&li style=&box-sizing: border- padding: 0px 5&&77&/li&&li style=&box-sizing: border- padding: 0px 5&&78&/li&&li style=&box-sizing: border- padding: 0px 5&&79&/li&&li style=&box-sizing: border- padding: 0px 5&&80&/li&&li style=&box-sizing: border- padding: 0px 5&&81&/li&&/ul&&ul class=&pre-numbering& style=&box-sizing: border- position: width: 50 top: 0 left: 0 margin: 0 padding: 6px 0px 40 border-right-width: 1 border-right-style: border-right-color: rgb(221, 221, 221); list-style: text-align: background-color: rgb(238, 238, 238);&&&li style=&box-sizing: border- padding: 0px 5&&1&/li&&li style=&box-sizing: border- padding: 0px 5&&2&/li&&li style=&box-sizing: border- padding: 0px 5&&3&/li&&li style=&box-sizing: border- padding: 0px 5&&4&/li&&li style=&box-sizing: border- padding: 0px 5&&5&/li&&li style=&box-sizing: border- padding: 0px 5&&6&/li&&li style=&box-sizing: border- padding: 0px 5&&7&/li&&li style=&box-sizing: border- padding: 0px 5&&8&/li&&li style=&box-sizing: border- padding: 0px 5&&9&/li&&li style=&box-sizing: border- padding: 0px 5&&10&/li&&li style=&box-sizing: border- padding: 0px 5&&11&/li&&li style=&box-sizing: border- padding: 0px 5&&12&/li&&li style=&box-sizing: border- padding: 0px 5&&13&/li&&li style=&box-sizing: border- padding: 0px 5&&14&/li&&li style=&box-sizing: border- padding: 0px 5&&15&/li&&li style=&box-sizing: border- padding: 0px 5&&16&/li&&li style=&box-sizing: border- padding: 0px 5&&17&/li&&li style=&box-sizing: border- padding: 0px 5&&18&/li&&li style=&box-sizing: border- padding: 0px 5&&19&/li&&li style=&box-sizing: border- padding: 0px 5&&20&/li&&li style=&box-sizing: border- padding: 0px 5&&21&/li&&li style=&box-sizing: border- padding: 0px 5&&22&/li&&li style=&box-sizing: border- padding: 0px 5&&23&/li&&li style=&box-sizing: border- padding: 0px 5&&24&/li&&li style=&box-sizing: border- padding: 0px 5&&25&/li&&li style=&box-sizing: border- padding: 0px 5&&26&/li&&li style=&box-sizing: border- padding: 0px 5&&27&/li&&li style=&box-sizing: border- padding: 0px 5&&28&/li&&li style=&box-sizing: border- padding: 0px 5&&29&/li&&li style=&box-sizing: border- padding: 0px 5&&30&/li&&li style=&box-sizing: border- padding: 0px 5&&31&/li&&li style=&box-sizing: border- padding: 0px 5&&32&/li&&li style=&box-sizing: border- padding: 0px 5&&33&/li&&li style=&box-sizing: border- padding: 0px 5&&34&/li&&li style=&box-sizing: border- padding: 0px 5&&35&/li&&li style=&box-sizing: border- padding: 0px 5&&36&/li&&li style=&box-sizing: border- padding: 0px 5&&37&/li&&li style=&box-sizing: border- padding: 0px 5&&38&/li&&li style=&box-sizing: border- padding: 0px 5&&39&/li&&li style=&box-sizing: border- padding: 0px 5&&40&/li&&li style=&box-sizing: border- padding: 0px 5&&41&/li&&li style=&box-sizing: border- padding: 0px 5&&42&/li&&li style=&box-sizing: border- padding: 0px 5&&43&/li&&li style=&box-sizing: border- padding: 0px 5&&44&/li&&li style=&box-sizing: border- padding: 0px 5&&45&/li&&li style=&box-sizing: border- padding: 0px 5&&46&/li&&li style=&box-sizing: border- padding: 0px 5&&47&/li&&li style=&box-sizing: border- padding: 0px 5&&48&/li&&li style=&box-sizing: border- padding: 0px 5&&49&/li&&li style=&box-sizing: border- padding: 0px 5&&50&/li&&li style=&box-sizing: border- padding: 0px 5&&51&/li&&li style=&box-sizing: border- padding: 0px 5&&52&/li&&li style=&box-sizing: border- padding: 0px 5&&53&/li&&li style=&box-sizing: border- padding: 0px 5&&54&/li&&li style=&box-sizing: border- padding: 0px 5&&55&/li&&li style=&box-sizing: border- padding: 0px 5&&56&/li&&li style=&box-sizing: border- padding: 0px 5&&57&/li&&li style=&box-sizing: border- padding: 0px 5&&58&/li&&li style=&box-sizing: border- padding: 0px 5&&59&/li&&li style=&box-sizing: border- padding: 0px 5&&60&/li&&li style=&box-sizing: border- padding: 0px 5&&61&/li&&li style=&box-sizing: border- padding: 0px 5&&62&/li&&li style=&box-sizing: border- padding: 0px 5&&63&/li&&li style=&box-sizing: border- padding: 0px 5&&64&/li&&li style=&box-sizing: border- padding: 0px 5&&65&/li&&li style=&box-sizing: border- padding: 0px 5&&66&/li&&li style=&box-sizing: border- padding: 0px 5&&67&/li&&li style=&box-sizing: border- padding: 0px 5&&68&/li&&li style=&box-sizing: border- padding: 0px 5&&69&/li&&li style=&box-sizing: border- padding: 0px 5&&70&/li&&li style=&box-sizing: border- padding: 0px 5&&71&/li&&li style=&box-sizing: border- padding: 0px 5&&72&/li&&li style=&box-sizing: border- padding: 0px 5&&73&/li&&li style=&box-sizing: border- padding: 0px 5&&74&/li&&li style=&box-sizing: border- padding: 0px 5&&75&/li&&li style=&box-sizing: border- padding: 0px 5&&76&/li&&li style=&box-sizing: border- padding: 0px 5&&77&/li&&li style=&box-sizing: border- padding: 0px 5&&78&/li&&li style=&box-sizing: border- padding: 0px 5&&79&/li&&li style=&box-sizing: border- padding: 0px 5&&80&/li&&li style=&box-sizing: border- padding: 0px 5&&81&/li&&/ul&
其关键代码就是在于设置：
&code class=&hljs glsl has-numbering& style=&display: padding: 0 color: box-sizing: border- font-family: 'Source Code Pro',font-size: white-space: border-radius: 0 word-wrap: background:&&mEffect = new DashPathEffect(new &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&float&/span&[]{&span class=&hljs-built_in& style=&color: rgb(102, 0, 102); box-sizing: border-&&length&/span&, &span class=&hljs-built_in& style=&color: rgb(102, 0, 102); box-sizing: border-&&length&/span&}, fraction * &span class=&hljs-built_in& style=&color: rgb(102, 0, 102); box-sizing: border-&&length&/span&);&/code&&ul class=&pre-numbering& style=&box-sizing: border- position: width: 50 top: 0 left: 0 margin: 0 padding: 6px 0px 40 border-right-width: 1 border-right-style: border-right-color: rgb(221, 221, 221); list-style: text-align: background-color: rgb(238, 238, 238);&&&li style=&box-sizing: border- padding: 0px 5&&1&/li&&/ul&&ul class=&pre-numbering& style=&box-sizing: border- position: width: 50 top: 0 left: 0 margin: 0 padding: 6px 0px 40 border-right-width: 1 border-right-style: border-right-color: rgb(221, 221, 221); list-style: text-align: background-color: rgb(238, 238, 238);&&&li style=&box-sizing: border- padding: 0px 5&&1&/li&&/ul&
后面通过属性动画来控制路径绘制即可。
坐标与切线
PathMeasure的getPosTan()方法，可以获取路径上的坐标点和对应点的切线坐标，其中，路径上对应的点非常好理解，就是对应的点的坐标，而另一个参数tan[]数组，它用于返回当前点的运动轨迹的斜率，要理解这个API，我们首先来看下Math中的atan2这个方法：
&code class=&hljs cs has-numbering& style=&display: padding: 0 color: box-sizing: border- font-family: 'Source Code Pro',font-size: white-space: border-radius: 0 word-wrap: background:&&&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&public&/span& &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&static&/span& &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&double&/span& &span class=&hljs-title& style=&box-sizing: border-&&atan2&/span& (&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&double&/span& y, &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&double&/span& x)&/code&&ul class=&pre-numbering& style=&box-sizing: border- position: width: 50 top: 0 left: 0 margin: 0 padding: 6px 0px 40 border-right-width: 1 border-right-style: border-right-color: rgb(221, 221, 221); list-style: text-align: background-color: rgb(238, 238, 238);&&&li style=&box-sizing: border- padding: 0px 5&&1&/li&&/ul&&ul class=&pre-numbering& style=&box-sizing: border- position: width: 50 top: 0 left: 0 margin: 0 padding: 6px 0px 40 border-right-width: 1 border-right-style: border-right-color: rgb(221, 221, 221); list-style: text-align: background-color: rgb(238, 238, 238);&&&li style=&box-sizing: border- padding: 0px 5&&1&/li&&/ul&
虽然atan()方法可以用于求一个反正切值，但是他传入的是一个角度，所以我们使用atan2()方法：
Math.atan2()函数返回点(x,y)和原点(0,0)之间直线的倾斜角
那么如何计算任意两点间直线的倾斜角呢?只需要将两点x,y坐标分别相减得到一个新的点(x2-x1,y2-y1)。然后利用它求出角度即可——Math.atan2(y2-y1,x2-x1)。
利用这个API，通常可以获取Path上的点坐标和点的运动趋势，对于运动趋势，通常通过Math.atan2()来转换为切线的角度，代码如下所示：
&code class=&hljs java has-numbering& style=&display: padding: 0 color: box-sizing: border- font-family: 'Source Code Pro',font-size: white-space: border-radius: 0 word-wrap: background:&&&span class=&hljs-annotation& style=&color: rgb(155, 133, 157); box-sizing: border-&&@Override&/span&
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&protected&/span& &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&void&/span& &span class=&hljs-title& style=&box-sizing: border-&&onDraw&/span&(Canvas canvas) {
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&super&/span&.onDraw(canvas);
mMeasure.getPosTan(mMeasure.getLength() * currentValue, pos, tan);
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&float&/span& degrees = (&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&float&/span&) (Math.atan2(tan[&span class=&hljs-number& style=&color: rgb(0, 102, 102); box-sizing: border-&&1&/span&], tan[&span class=&hljs-number& style=&color: rgb(0, 102, 102); box-sizing: border-&&0&/span&]) * &span class=&hljs-number& style=&color: rgb(0, 102, 102); box-sizing: border-&&180.0&/span& / Math.PI);
}&/code&&ul class=&pre-numbering& style=&box-sizing: border- position: width: 50 top: 0 left: 0 margin: 0 padding: 6px 0px 40 border-right-width: 1 border-right-style: border-right-color: rgb(221, 221, 221); list-style: text-align: background-color: rgb(238, 238, 238);&&&li style=&box-sizing: border- padding: 0px 5&&1&/li&&li style=&box-sizing: border- padding: 0px 5&&2&/li&&li style=&box-sizing: border- padding: 0px 5&&3&/li&&li style=&box-sizing: border- padding: 0px 5&&4&/li&&li style=&box-sizing: border- padding: 0px 5&&5&/li&&li style=&box-sizing: border- padding: 0px 5&&6&/li&&/ul&&ul class=&pre-numbering& style=&box-sizing: border- position: width: 50 top: 0 left: 0 margin: 0 padding: 6px 0px 40 border-right-width: 1 border-right-style: border-right-color: rgb(221, 221, 221); list-style: text-align: background-color: rgb(238, 238, 238);&&&li style=&box-sizing: border- padding: 0px 5&&1&/li&&li style=&box-sizing: border- padding: 0px 5&&2&/li&&li style=&box-sizing: border- padding: 0px 5&&3&/li&&li style=&box-sizing: border- padding: 0px 5&&4&/li&&li style=&box-sizing: border- padding: 0px 5&&5&/li&&li style=&box-sizing: border- padding: 0px 5&&6&/li&&/ul&
根据这个API，我们可以模拟一个圆上的点和点的运动趋势，代码如下：
&code class=&hljs java has-numbering& style=&display: padding: 0 color: box-sizing: border- font-family: 'Source Code Pro',font-size: white-space: border-radius: 0 word-wrap: background:&&&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&package&/span& .pathart.
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&import&/span& android.animation.ValueA
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&import&/span& android.content.C
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&import&/span& android.graphics.C
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&import&/span& android.graphics.P
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&import&/span& android.graphics.P
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&import&/span& android.graphics.PathM
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&import&/span& android.util.AttributeS
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&import&/span& android.view.V
&span class=&hljs-javadoc& style=&color: rgb(136, 0, 0); box-sizing: border-&&/**
* 曲线上切点
* Created by xuyisheng on 16/7/15.
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&public&/span& &span class=&hljs-class& style=&box-sizing: border-&&&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&class&/span& &span class=&hljs-title& style=&box-sizing: border- color: rgb(102, 0, 102);&&PathTan&/span& &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&extends&/span& &span class=&hljs-title& style=&box-sizing: border- color: rgb(102, 0, 102);&&View&/span& &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&implements&/span& &span class=&hljs-title& style=&box-sizing: border- color: rgb(102, 0, 102);&&View&/span&.&span class=&hljs-title& style=&box-sizing: border- color: rgb(102, 0, 102);&&OnClickListener&/span& {&/span&
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&private&/span& Path mP
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&private&/span& &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&float&/span&[]
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&private&/span& &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&float&/span&[]
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&private&/span& Paint mP
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&float&/span& currentValue = &span class=&hljs-number& style=&color: rgb(0, 102, 102); box-sizing: border-&&0&/span&;
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&private&/span& PathMeasure mM
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&public&/span& &span class=&hljs-title& style=&box-sizing: border-&&PathTan&/span&(Context context) {
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&super&/span&(context);
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&public&/span& &span class=&hljs-title& style=&box-sizing: border-&&PathTan&/span&(Context context, AttributeSet attrs) {
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&super&/span&(context, attrs);
mPath = &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&new&/span& Path();
mPaint = &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&new&/span& Paint();
mPaint.setStyle(Paint.Style.STROKE);
mPaint.setStrokeWidth(&span class=&hljs-number& style=&color: rgb(0, 102, 102); box-sizing: border-&&4&/span&);
mMeasure = &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&new&/span& PathMeasure();
mPath.addCircle(&span class=&hljs-number& style=&color: rgb(0, 102, 102); box-sizing: border-&&0&/span&, &span class=&hljs-number& style=&color: rgb(0, 102, 102); box-sizing: border-&&0&/span&, &span class=&hljs-number& style=&color: rgb(0, 102, 102); box-sizing: border-&&200&/span&, Path.Direction.CW);
mMeasure.setPath(mPath, &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&false&/span&);
pos = &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&new&/span& &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&float&/span&[&span class=&hljs-number& style=&color: rgb(0, 102, 102); box-sizing: border-&&2&/span&];
tan = &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&new&/span& &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&float&/span&[&span class=&hljs-number& style=&color: rgb(0, 102, 102); box-sizing: border-&&2&/span&];
setOnClickListener(&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&this&/span&);
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&public&/span& &span class=&hljs-title& style=&box-sizing: border-&&PathTan&/span&(Context context, AttributeSet attrs, &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&int&/span& defStyleAttr) {
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&super&/span&(context, attrs, defStyleAttr);
&span class=&hljs-annotation& style=&color: rgb(155, 133, 157); box-sizing: border-&&@Override&/span&
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&protected&/span& &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&void&/span& &span class=&hljs-title& style=&box-sizing: border-&&onDraw&/span&(Canvas canvas) {
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&super&/span&.onDraw(canvas);
mMeasure.getPosTan(mMeasure.getLength() * currentValue, pos, tan);
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&float&/span& degrees = (&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&float&/span&) (Math.atan2(tan[&span class=&hljs-number& style=&color: rgb(0, 102, 102); box-sizing: border-&&1&/span&], tan[&span class=&hljs-number& style=&color: rgb(0, 102, 102); box-sizing: border-&&0&/span&]) * &span class=&hljs-number& style=&color: rgb(0, 102, 102); box-sizing: border-&&180.0&/span& / Math.PI);
canvas.save();
canvas.translate(&span class=&hljs-number& style=&color: rgb(0, 102, 102); box-sizing: border-&&400&/span&, &span class=&hljs-number& style=&color: rgb(0, 102, 102); box-sizing: border-&&400&/span&);
canvas.drawPath(mPath, mPaint);
canvas.drawCircle(pos[&span class=&hljs-number& style=&color: rgb(0, 102, 102); box-sizing: border-&&0&/span&], pos[&span class=&hljs-number& style=&color: rgb(0, 102, 102); box-sizing: border-&&1&/span&], &span class=&hljs-number& style=&color: rgb(0, 102, 102); box-sizing: border-&&10&/span&, mPaint);
canvas.rotate(degrees);
canvas.drawLine(&span class=&hljs-number& style=&color: rgb(0, 102, 102); box-sizing: border-&&0&/span&, -&span class=&hljs-number& style=&color: rgb(0, 102, 102); box-sizing: border-&&200&/span&, &span class=&hljs-number& style=&color: rgb(0, 102, 102); box-sizing: border-&&300&/span&, -&span class=&hljs-number& style=&color: rgb(0, 102, 102); box-sizing: border-&&200&/span&, mPaint);
canvas.restore();
&span class=&hljs-annotation& style=&color: rgb(155, 133, 157); box-sizing: border-&&@Override&/span&
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&public&/span& &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&void&/span& &span class=&hljs-title& style=&box-sizing: border-&&onClick&/span&(View view) {
ValueAnimator animator = ValueAnimator.ofFloat(&span class=&hljs-number& style=&color: rgb(0, 102, 102); box-sizing: border-&&0&/span&, &span class=&hljs-number& style=&color: rgb(0, 102, 102); box-sizing: border-&&1&/span&);
animator.addUpdateListener(&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&new&/span& ValueAnimator.AnimatorUpdateListener() {
&span class=&hljs-annotation& style=&color: rgb(155, 133, 157); box-sizing: border-&&@Override&/span&
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&public&/span& &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&void&/span& &span class=&hljs-title& style=&box-sizing: border-&&onAnimationUpdate&/span&(ValueAnimator valueAnimator) {
currentValue = (&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&float&/span&) valueAnimator.getAnimatedValue();
invalidate();
animator.setDuration(&span class=&hljs-number& style=&color: rgb(0, 102, 102); box-sizing: border-&&3000&/span&);
animator.setRepeatCount(ValueAnimator.INFINITE);
animator.start();
&/code&&ul class=&pre-numbering& style=&box-sizing: border- position: width: 50 top: 0 left: 0 margin: 0 padding: 6px 0px 40 border-right-width: 1 border-right-style: border-right-color: rgb(221, 221, 221); list-style: text-align: background-color: rgb(238, 238, 238);&&&li style=&box-sizing: border- padding: 0px 5&&1&/li&&li style=&box-sizing: border- padding: 0px 5&&2&/li&&li style=&box-sizing: border- padding: 0px 5&&3&/li&&li style=&box-sizing: border- padding: 0px 5&&4&/li&&li style=&box-sizing: border- padding: 0px 5&&5&/li&&li style=&box-sizing: border- padding: 0px 5&&6&/li&&li style=&box-sizing: border- padding: 0px 5&&7&/li&&li style=&box-sizing: border- padding: 0px 5&&8&/li&&li style=&box-sizing: border- padding: 0px 5&&9&/li&&li style=&box-sizing: border- padding: 0px 5&&10&/li&&li style=&box-sizing: border- padding: 0px 5&&11&/li&&li style=&box-sizing: border- padding: 0px 5&&12&/li&&li style=&box-sizing: border- padding: 0px 5&&13&/li&&li style=&box-sizing: border- padding: 0px 5&&14&/li&&li style=&box-sizing: border- padding: 0px 5&&15&/li&&li style=&box-sizing: border- padding: 0px 5&&16&/li&&li style=&box-sizing: border- padding: 0px 5&&17&/li&&li style=&box-sizing: border- padding: 0px 5&&18&/li&&li style=&box-sizing: border- padding: 0px 5&&19&/li&&li style=&box-sizing: border- padding: 0px 5&&20&/li&&li style=&box-sizing: border- padding: 0px 5&&21&/li&&li style=&box-sizing: border- padding: 0px 5&&22&/li&&li style=&box-sizing: border- padding: 0px 5&&23&/li&&li style=&box-sizing: border- padding: 0px 5&&24&/li&&li style=&box-sizing: border- padding: 0px 5&&25&/li&&li style=&box-sizing: border- padding: 0px 5&&26&/li&&li style=&box-sizing: border- padding: 0px 5&&27&/li&&li style=&box-sizing: border- padding: 0px 5&&28&/li&&li style=&box-sizing: border- padding: 0px 5&&29&/li&&li style=&box-sizing: border- padding: 0px 5&&30&/li&&li style=&box-sizing: border- padding: 0px 5&&31&/li&&li style=&box-sizing: border- padding: 0px 5&&32&/li&&li style=&box-sizing: border- padding: 0px 5&&33&/li&&li style=&box-sizing: border- padding: 0px 5&&34&/li&&li style=&box-sizing: border- padding: 0px 5&&35&/li&&li style=&box-sizing: border- padding: 0px 5&&36&/li&&li style=&box-sizing: border- padding: 0px 5&&37&/li&&li style=&box-sizing: border- padding: 0px 5&&38&/li&&li style=&box-sizing: border- padding: 0px 5&&39&/li&&li style=&box-sizing: border- padding: 0px 5&&40&/li&&li style=&box-sizing: border- padding: 0px 5&&41&/li&&li style=&box-sizing: border- padding: 0px 5&&42&/li&&li style=&box-sizing: border- padding: 0px 5&&43&/li&&li style=&box-sizing: border- padding: 0px 5&&44&/li&&li style=&box-sizing: border- padding: 0px 5&&45&/li&&li style=&box-sizing: border- padding: 0px 5&&46&/li&&li style=&box-sizing: border- padding: 0px 5&&47&/li&&li style=&box-sizing: border- padding: 0px 5&&48&/li&&li style=&box-sizing: border- padding: 0px 5&&49&/li&&li style=&box-sizing: border- padding: 0px 5&&50&/li&&li style=&box-sizing: border- padding: 0px 5&&51&/li&&li style=&box-sizing: border- padding: 0px 5&&52&/li&&li style=&box-sizing: border- padding: 0px 5&&53&/li&&li style=&box-sizing: border- padding: 0px 5&&54&/li&&li style=&box-sizing: border- padding: 0px 5&&55&/li&&li style=&box-sizing: border- padding: 0px 5&&56&/li&&li style=&box-sizing: border- padding: 0px 5&&57&/li&&li style=&box-sizing: border- padding: 0px 5&&58&/li&&li style=&box-sizing: border- padding: 0px 5&&59&/li&&li style=&box-sizing: border- padding: 0px 5&&60&/li&&li style=&box-sizing: border- padding: 0px 5&&61&/li&&li style=&box-sizing: border- padding: 0px 5&&62&/li&&li style=&box-sizing: border- padding: 0px 5&&63&/li&&li style=&box-sizing: border- padding: 0px 5&&64&/li&&li style=&box-sizing: border- padding: 0px 5&&65&/li&&li style=&box-sizing: border- padding: 0px 5&&66&/li&&li style=&box-sizing: border- padding: 0px 5&&67&/li&&li style=&box-sizing: border- padding: 0px 5&&68&/li&&li style=&box-sizing: border- padding: 0px 5&&69&/li&&li style=&box-sizing: border- padding: 0px 5&&70&/li&&li style=&box-sizing: border- padding: 0px 5&&71&/li&&li style=&box-sizing: border- padding: 0px 5&&72&/li&&li style=&box-sizing: border- padding: 0px 5&&73&/li&&li style=&box-sizing: border- padding: 0px 5&&74&/li&&li style=&box-sizing: border- padding: 0px 5&&75&/li&&li style=&box-sizing: border- padding: 0px 5&&76&/li&&li style=&box-sizing: border- padding: 0px 5&&77&/li&&li style=&box-sizing: border- padding: 0px 5&&78&/li&&/ul&&ul class=&pre-numbering& style=&box-sizing: border- position: width: 50 top: 0 left: 0 margin: 0 padding: 6px 0px 40 border-right-width: 1 border-right-style: border-right-color: rgb(221, 221, 221); list-style: text-align: background-color: rgb(238, 238, 238);&&&li style=&box-sizing: border- padding: 0px 5&&1&/li&&li style=&box-sizing: border- padding: 0px 5&&2&/li&&li style=&box-sizing: border- padding: 0px 5&&3&/li&&li style=&box-sizing: border- padding: 0px 5&&4&/li&&li style=&box-sizing: border- padding: 0px 5&&5&/li&&li style=&box-sizing: border- padding: 0px 5&&6&/li&&li style=&box-sizing: border- padding: 0px 5&&7&/li&&li style=&box-sizing: border- padding: 0px 5&&8&/li&&li style=&box-sizing: border- padding: 0px 5&&9&/li&&li style=&box-sizing: border- padding: 0px 5&&10&/li&&li style=&box-sizing: border- padding: 0px 5&&11&/li&&li style=&box-sizing: border- padding: 0px 5&&12&/li&&li style=&box-sizing: border- padding: 0px 5&&13&/li&&li style=&box-sizing: border- padding: 0px 5&&14&/li&&li style=&box-sizing: border- padding: 0px 5&&15&/li&&li style=&box-sizing: border- padding: 0px 5&&16&/li&&li style=&box-sizing: border- padding: 0px 5&&17&/li&&li style=&box-sizing: border- padding: 0px 5&&18&/li&&li style=&box-sizing: border- padding: 0px 5&&19&/li&&li style=&box-sizing: border- padding: 0px 5&&20&/li&&li style=&box-sizing: border- padding: 0px 5&&21&/li&&li style=&box-sizing: border- padding: 0px 5&&22&/li&&li style=&box-sizing: border- padding: 0px 5&&23&/li&&li style=&box-sizing: border- padding: 0px 5&&24&/li&&li style=&box-sizing: border- padding: 0px 5&&25&/li&&li style=&box-sizing: border- padding: 0px 5&&26&/li&&li style=&box-sizing: border- padding: 0px 5&&27&/li&&li style=&box-sizing: border- padding: 0px 5&&28&/li&&li style=&box-sizing: border- padding: 0px 5&&29&/li&&li style=&box-sizing: border- padding: 0px 5&&30&/li&&li style=&box-sizing: border- padding: 0px 5&&31&/li&&li style=&box-sizing: border- padding: 0px 5&&32&/li&&li style=&box-sizing: border- padding: 0px 5&&33&/li&&li style=&box-sizing: border- padding: 0px 5&&34&/li&&li style=&box-sizing: border- padding: 0px 5&&35&/li&&li style=&box-sizing: border- padding: 0px 5&&36&/li&&li style=&box-sizing: border- padding: 0px 5&&37&/li&&li style=&box-sizing: border- padding: 0px 5&&38&/li&&li style=&box-sizing: border- padding: 0px 5&&39&/li&&li style=&box-sizing: border- padding: 0px 5&&40&/li&&li style=&box-sizing: border- padding: 0px 5&&41&/li&&li style=&box-sizing: border- padding: 0px 5&&42&/li&&li style=&box-sizing: border- padding: 0px 5&&43&/li&&li style=&box-sizing: border- padding: 0px 5&&44&/li&&li style=&box-sizing: border- padding: 0px 5&&45&/li&&li style=&box-sizing: border- padding: 0px 5&&46&/li&&li style=&box-sizing: border- padding: 0px 5&&47&/li&&li style=&box-sizing: border- padding: 0px 5&&48&/li&&li style=&box-sizing: border- padding: 0px 5&&49&/li&&li style=&box-sizing: border- padding: 0px 5&&50&/li&&li style=&box-sizing: border- padding: 0px 5&&51&/li&&li style=&box-sizing: border- padding: 0px 5&&52&/li&&li style=&box-sizing: border- padding: 0px 5&&53&/li&&li style=&box-sizing: border- padding: 0px 5&&54&/li&&li style=&box-sizing: border- padding: 0px 5&&55&/li&&li style=&box-sizing: border- padding: 0px 5&&56&/li&&li style=&box-sizing: border- padding: 0px 5&&57&/li&&li style=&box-sizing: border- padding: 0px 5&&58&/li&&li style=&box-sizing: border- padding: 0px 5&&59&/li&&li style=&box-sizing: border- padding: 0px 5&&60&/li&&li style=&box-sizing: border- padding: 0px 5&&61&/li&&li style=&box-sizing: border- padding: 0px 5&&62&/li&&li style=&box-sizing: border- padding: 0px 5&&63&/li&&li style=&box-sizing: border- padding: 0px 5&&64&/li&&li style=&box-sizing: border- padding: 0px 5&&65&/li&&li style=&box-sizing: border- padding: 0px 5&&66&/li&&li style=&box-sizing: border- padding: 0px 5&&67&/li&&li style=&box-sizing: border- padding: 0px 5&&68&/li&&li style=&box-sizing: border- padding: 0px 5&&69&/li&&li style=&box-sizing: border- padding: 0px 5&&70&/li&&li style=&box-sizing: border- padding: 0px 5&&71&/li&&li style=&box-sizing: border- padding: 0px 5&&72&/li&&li style=&box-sizing: border- padding: 0px 5&&73&/li&&li style=&box-sizing: border- padding: 0px 5&&74&/li&&li style=&box-sizing: border- padding: 0px 5&&75&/li&&li style=&box-sizing: border- padding: 0px 5&&76&/li&&li style=&box-sizing: border- padding: 0px 5&&77&/li&&li style=&box-sizing: border- padding: 0px 5&&78&/li&&/ul&
Demo效果如图所示：
只不过这里在绘制的时候，使用了一些Trick，先通过canvas.translate方法将原点移动的圆心，同时，通过canvas.rotate将运动趋势的角度转换为画布的旋转，这样每次绘制切线，就只需要画一条同样的切线即可。
阅读排行榜}
本帖子已过去太久远了，不再提供回复功能。> 问题详情
求解Java程序设计编写一个日期对应的星期几程序
悬赏：0&答案豆
提问人：匿名网友
发布时间：
求解Java程序设计编写一个日期对应的星期几程序
论文写作技巧
我有更好的答案
请先输入下方的验证码查看最佳答案
图形验证：
验证码提交中……PathMeasure之迷径追踪
Path，不论是在自定义View还是动画，都占有举足轻重的地位。绘制Path，可以通过提供的API，或者是贝塞尔曲线、数学函数、图形组合等等方式，而要获取Path上每一个构成点的坐标，一般需要知道Path的函数方法，例如求解贝塞尔曲线上的点的De
Casteljau算法，但对于一般的Path来说，是很难通过简单的函数方法来进行计算的，那么，如何来定位任意一个给定Path的任意一个点的坐标呢？
Android SDK提供了一个非常有用的API来帮助开发者实现这样一个Path路径点的坐标追踪，这个类就是PathMeasure，它可以认为是一个Path的坐标计算器。
PathMeasure类似一个计算器，对它进行初始化只需要new一个PathMeasure对象即可：
&code class=&hljs fix has-numbering& style=&display: padding: 0 color: box-sizing: border- font-family: 'Source Code Pro',font-size: white-space: border-radius: 0 word-wrap: background:&&&span class=&hljs-attribute& style=&box-sizing: border-&&PathMeasure pathMeasure &/span&=&span class=&hljs-string& style=&color: rgb(0, 136, 0); box-sizing: border-&& new PathMeasure();&/span&&/code&&ul class=&pre-numbering& style=&box-sizing: border- position: width: 50 top: 0 left: 0 margin: 0 padding: 6px 0px 40 border-right-width: 1 border-right-style: border-right-color: rgb(221, 221, 221); list-style: text-align: background-color: rgb(238, 238, 238);&&&li style=&box-sizing: border- padding: 0px 5&&1&/li&&/ul&&ul class=&pre-numbering& style=&box-sizing: border- position: width: 50 top: 0 left: 0 margin: 0 padding: 6px 0px 40 border-right-width: 1 border-right-style: border-right-color: rgb(221, 221, 221); list-style: text-align: background-color: rgb(238, 238, 238);&&&li style=&box-sizing: border- padding: 0px 5&&1&/li&&/ul&
初始化PathMeasure后，可以通过PathMeasure.setPath()的方式来将Path和PathMeasure进行绑定，例如：
&code class=&hljs bash has-numbering& style=&display: padding: 0 color: box-sizing: border- font-family: 'Source Code Pro',font-size: white-space: border-radius: 0 word-wrap: background:&&pathMeasure.setPath(path, &span class=&hljs-literal& style=&color: rgb(0, 102, 102); box-sizing: border-&&true&/span&);&/code&&ul class=&pre-numbering& style=&box-sizing: border- position: width: 50 top: 0 left: 0 margin: 0 padding: 6px 0px 40 border-right-width: 1 border-right-style: border-right-color: rgb(221, 221, 221); list-style: text-align: background-color: rgb(238, 238, 238);&&&li style=&box-sizing: border- padding: 0px 5&&1&/li&&/ul&&ul class=&pre-numbering& style=&box-sizing: border- position: width: 50 top: 0 left: 0 margin: 0 padding: 6px 0px 40 border-right-width: 1 border-right-style: border-right-color: rgb(221, 221, 221); list-style: text-align: background-color: rgb(238, 238, 238);&&&li style=&box-sizing: border- padding: 0px 5&&1&/li&&/ul&
当然，你也可以直接使用PathMeasure的有参构造方法来进行初始化：
&code class=&hljs java has-numbering& style=&display: padding: 0 color: box-sizing: border- font-family: 'Source Code Pro',font-size: white-space: border-radius: 0 word-wrap: background:&&PathMeasure (Path path, &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&boolean&/span& forceClosed)&/code&&ul class=&pre-numbering& style=&box-sizing: border- position: width: 50 top: 0 left: 0 margin: 0 padding: 6px 0px 40 border-right-width: 1 border-right-style: border-right-color: rgb(221, 221, 221); list-style: text-align: background-color: rgb(238, 238, 238);&&&li style=&box-sizing: border- padding: 0px 5&&1&/li&&/ul&&ul class=&pre-numbering& style=&box-sizing: border- position: width: 50 top: 0 left: 0 margin: 0 padding: 6px 0px 40 border-right-width: 1 border-right-style: border-right-color: rgb(221, 221, 221); list-style: text-align: background-color: rgb(238, 238, 238);&&&li style=&box-sizing: border- padding: 0px 5&&1&/li&&/ul&
这里最不容易理解的就是第二个boolean参数forceClosed。
forceClosed参数
这个参数——forceClosed，简单的说，就是Path最终是否需要闭合，如果为True的话，则不管关联的Path是否是闭合的，都会被闭合。
但是这个参数对Path和PathMeasure的影响是需要解释下的：
forceClosed参数对绑定的Path不会产生任何影响，例如一个折线段的Path，本身是没有闭合的，forceClosed设置为True的时候，PathMeasure计算的Path是闭合的，但Path本身绘制出来是不会闭合的。forceClosed参数对PathMeasure的测量结果有影响，还是例如前面说的一个折线段的Path，本身没有闭合，forceClosed设置为True，PathMeasure的计算就会包含最后一段闭合的路径，与原来的Path不同。
PathMeasure的API非常容易理解，几乎都是望文生义。
PathMeasure.getLength()的使用非常广泛，其作用就是获取计算的路径长度。
getSegment
&code class=&hljs java has-numbering& style=&display: padding: 0 color: box-sizing: border- font-family: 'Source Code Pro',font-size: white-space: border-radius: 0 word-wrap: background:&&&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&boolean&/span& getSegment (&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&float&/span& startD, &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&float&/span& stopD, Path dst, &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&boolean&/span& startWithMoveTo)&/code&&ul class=&pre-numbering& style=&box-sizing: border- position: width: 50 top: 0 left: 0 margin: 0 padding: 6px 0px 40 border-right-width: 1 border-right-style: border-right-color: rgb(221, 221, 221); list-style: text-align: background-color: rgb(238, 238, 238);&&&li style=&box-sizing: border- padding: 0px 5&&1&/li&&/ul&&ul class=&pre-numbering& style=&box-sizing: border- position: width: 50 top: 0 left: 0 margin: 0 padding: 6px 0px 40 border-right-width: 1 border-right-style: border-right-color: rgb(221, 221, 221); list-style: text-align: background-color: rgb(238, 238, 238);&&&li style=&box-sizing: border- padding: 0px 5&&1&/li&&/ul&
这个API用于截取整个Path的片段，通过参数startD和stopD来控制截取的长度，并将截取的Path保存到dst中，最后一个参数startWithMoveTo表示起始点是否使用moveTo方法，通常为True，保证每次截取的Path片段都是正常的、完整的。
如果startWithMoveTo设置为false，通常是和dst一起使用，因为dst中保存的Path是被不断添加的，而不是每次被覆盖，设置为false，则新增的片段会从上一次Path终点开始计算，这样可以保存截取的Path片段数组连续起来。
nextContour
nextContour()方法用的比较少，比较大部分情况下都只会有一个Path而不是多个，毕竟这样会增加Path的复杂度，但是如果真有一个Path，包含了多个Path，那么通过nextContour这个方法，就可以进行切换，同时，默认的API，例如getLength，获取的也是当前的这段Path所对应的长度，而不是所有的Path的长度，同时，nextContour获取Path的顺序，与Path的添加顺序是相同的。
&code class=&hljs glsl has-numbering& style=&display: padding: 0 color: box-sizing: border- font-family: 'Source Code Pro',font-size: white-space: border-radius: 0 word-wrap: background:&&boolean getPosTan (&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&float&/span& &span class=&hljs-built_in& style=&color: rgb(102, 0, 102); box-sizing: border-&&distance&/span&, &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&float&/span&[] pos, &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&float&/span&[] &span class=&hljs-built_in& style=&color: rgb(102, 0, 102); box-sizing: border-&&tan&/span&)&/code&&ul class=&pre-numbering& style=&box-sizing: border- position: width: 50 top: 0 left: 0 margin: 0 padding: 6px 0px 40 border-right-width: 1 border-right-style: border-right-color: rgb(221, 221, 221); list-style: text-align: background-color: rgb(238, 238, 238);&&&li style=&box-sizing: border- padding: 0px 5&&1&/li&&/ul&&ul class=&pre-numbering& style=&box-sizing: border- position: width: 50 top: 0 left: 0 margin: 0 padding: 6px 0px 40 border-right-width: 1 border-right-style: border-right-color: rgb(221, 221, 221); list-style: text-align: background-color: rgb(238, 238, 238);&&&li style=&box-sizing: border- padding: 0px 5&&1&/li&&/ul&
这个API用于获取路径上某点的坐标及其切线的坐标，这个API非常强大，但是比较难理解，后面会结合例子来讲解。
简单的说，就是通过指定distance（0
硬件加速的Bug
由于硬件加速的问题，PathMeasure中的getSegment在讲Path添加到dst数组中时会被导致一些错误，需要通过mDst.lineTo(0,0)来避免这样一个Bug。
路径绘制是PathMeasure最常用的功能，其原理就是通过getSegment来不断截取Path片段，从而不断绘制完整的路径，效果如图所示：
代码如下所示：
&code class=&hljs java has-numbering& style=&display: padding: 0 color: box-sizing: border- font-family: 'Source Code Pro',font-size: white-space: border-radius: 0 word-wrap: background:&&&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&package&/span& .pathart.
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&import&/span& android.animation.ValueA
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&import&/span& android.content.C
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&import&/span& android.graphics.C
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&import&/span& android.graphics.P
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&import&/span& android.graphics.P
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&import&/span& android.graphics.PathM
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&import&/span& android.util.AttributeS
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&import&/span& android.view.V
&span class=&hljs-javadoc& style=&color: rgb(136, 0, 0); box-sizing: border-&&/**
* 路径动画 PathMeasure
* Created by xuyisheng on 16/7/15.
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&public&/span& &span class=&hljs-class& style=&box-sizing: border-&&&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&class&/span& &span class=&hljs-title& style=&box-sizing: border- color: rgb(102, 0, 102);&&PathPainter&/span& &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&extends&/span& &span class=&hljs-title& style=&box-sizing: border- color: rgb(102, 0, 102);&&View&/span& {&/span&
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&private&/span& Path mP
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&private&/span& Paint mP
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&private&/span& PathMeasure mPathM
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&private&/span& &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&float&/span& mAnimatorV
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&private&/span& Path mD
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&private&/span& &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&float&/span& mL
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&public&/span& &span class=&hljs-title& style=&box-sizing: border-&&PathPainter&/span&(Context context) {
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&super&/span&(context);
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&public&/span& &span class=&hljs-title& style=&box-sizing: border-&&PathPainter&/span&(Context context, AttributeSet attrs) {
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&super&/span&(context, attrs);
mPathMeasure = &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&new&/span& PathMeasure();
mPaint = &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&new&/span& Paint(Paint.ANTI_ALIAS_FLAG);
mPaint.setStyle(Paint.Style.STROKE);
mPaint.setStrokeWidth(&span class=&hljs-number& style=&color: rgb(0, 102, 102); box-sizing: border-&&5&/span&);
mPath = &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&new&/span& Path();
mPath.addCircle(&span class=&hljs-number& style=&color: rgb(0, 102, 102); box-sizing: border-&&400&/span&, &span class=&hljs-number& style=&color: rgb(0, 102, 102); box-sizing: border-&&400&/span&, &span class=&hljs-number& style=&color: rgb(0, 102, 102); box-sizing: border-&&100&/span&, Path.Direction.CW);
mPathMeasure.setPath(mPath, &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&true&/span&);
mLength = mPathMeasure.getLength();
mDst = &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&new&/span& Path();
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&final&/span& ValueAnimator valueAnimator = ValueAnimator.ofFloat(&span class=&hljs-number& style=&color: rgb(0, 102, 102); box-sizing: border-&&0&/span&, &span class=&hljs-number& style=&color: rgb(0, 102, 102); box-sizing: border-&&1&/span&);
valueAnimator.addUpdateListener(&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&new&/span& ValueAnimator.AnimatorUpdateListener() {
&span class=&hljs-annotation& style=&color: rgb(155, 133, 157); box-sizing: border-&&@Override&/span&
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&public&/span& &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&void&/span& &span class=&hljs-title& style=&box-sizing: border-&&onAnimationUpdate&/span&(ValueAnimator valueAnimator) {
mAnimatorValue = (&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&float&/span&) valueAnimator.getAnimatedValue();
invalidate();
valueAnimator.setDuration(&span class=&hljs-number& style=&color: rgb(0, 102, 102); box-sizing: border-&&2000&/span&);
valueAnimator.setRepeatCount(ValueAnimator.INFINITE);
valueAnimator.start();
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&public&/span& &span class=&hljs-title& style=&box-sizing: border-&&PathPainter&/span&(Context context, AttributeSet attrs, &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&int&/span& defStyleAttr) {
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&super&/span&(context, attrs, defStyleAttr);
&span class=&hljs-annotation& style=&color: rgb(155, 133, 157); box-sizing: border-&&@Override&/span&
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&protected&/span& &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&void&/span& &span class=&hljs-title& style=&box-sizing: border-&&onDraw&/span&(Canvas canvas) {
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&super&/span&.onDraw(canvas);
mDst.reset();
&span class=&hljs-comment& style=&color: rgb(136, 0, 0); box-sizing: border-&&// 硬件加速的BUG&/span&
mDst.lineTo(&span class=&hljs-number& style=&color: rgb(0, 102, 102); box-sizing: border-&&0&/span&,&span class=&hljs-number& style=&color: rgb(0, 102, 102); box-sizing: border-&&0&/span&);
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&float&/span& stop = mLength * mAnimatorV
mPathMeasure.getSegment(&span class=&hljs-number& style=&color: rgb(0, 102, 102); box-sizing: border-&&0&/span&, stop, mDst, &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&true&/span&);
canvas.drawPath(mDst, mPaint);
&/code&&p&&code class=&hljs java has-numbering& style=&display: padding: 0 color: box-sizing: border- font-family: 'Source Code Pro',font-size: white-space: border-radius: 0 word-wrap: background:&&
}&/code&&code class=&hljs java has-numbering& style=&display: padding: 0 color: box-sizing: border- font-family: 'Source Code Pro',font-size: white-space: border-radius: 0 word-wrap: background:&&
&/code&&code class=&hljs java has-numbering& style=&display: padding: 0 color: box-sizing: border- font-family: 'Source Code Pro',font-size: white-space: border-radius: 0 word-wrap: background:&&
&/code&&code class=&hljs java has-numbering& style=&display: padding: 0 color: box-sizing: border- font-family: 'Source Code Pro',font-size: white-space: border-radius: 0 word-wrap: background:&&&/code&&/p&&p style=&margin-top: 0 margin-bottom: 1.1 padding-top: 0 padding-bottom: 0 box-sizing: border- color: rgb(85, 85, 85); font-family: 'microsoft yahei'; font-size: 14 line-height: 35&&通过这种方式，只需要做一点点小的修改，就可以完成一个比较有意思的loading图，效果如下所示：&/p&&p style=&margin-top: 0 margin-bottom: 1.1 padding-top: 0 padding-bottom: 0 box-sizing: border- color: rgb(85, 85, 85); font-family: 'microsoft yahei'; font-size: 14 line-height: 35&&&img src=&http://img.blog.csdn.net/13306& alt=&这里写图片描述& title=&& style=&border: box-sizing: border- max-width: 602 height:& /&&/p&&p style=&margin-top: 0 margin-bottom: 1.1 padding-top: 0 padding-bottom: 0 box-sizing: border- color: rgb(85, 85, 85); font-family: 'microsoft yahei'; font-size: 14 line-height: 35&&我们只需要修改下起始值的数字即可，关键代码如下：&/p&&pre class=&prettyprint& name=&code& style=&white-space: word-wrap: break- box-sizing: border- position: overflow-y: overflow-x: margin-top: 0 margin-bottom: 1.1 font-family: 'Source Code Pro', padding: 5px 5px 5px 60 font-size: 14 line-height: 1.45; word-break: break- color: rgb(51, 51, 51); border: 1px solid rgba(128, 128, 128, 0.0745098); border-radius: 0 background-color: rgba(128, 128, 128, 0.0470588);&&&code class=&hljs java has-numbering& style=&display: padding: 0 color: box-sizing: border- font-family: 'Source Code Pro',font-size: white-space: border-radius: 0 word-wrap: background:&&&span class=&hljs-annotation& style=&color: rgb(155, 133, 157); box-sizing: border-&&@Override&/span&
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&protected&/span& &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&void&/span& &span class=&hljs-title& style=&box-sizing: border-&&onDraw&/span&(Canvas canvas) {
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&super&/span&.onDraw(canvas);
mDst.reset();
&span class=&hljs-comment& style=&color: rgb(136, 0, 0); box-sizing: border-&&// 硬件加速的BUG&/span&
mDst.lineTo(&span class=&hljs-number& style=&color: rgb(0, 102, 102); box-sizing: border-&&0&/span&,&span class=&hljs-number& style=&color: rgb(0, 102, 102); box-sizing: border-&&0&/span&);
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&float&/span& stop = mLength * mAnimatorV
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&float&/span& start = (&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&float&/span&) (stop - ((&span class=&hljs-number& style=&color: rgb(0, 102, 102); box-sizing: border-&&0.5&/span& - Math.abs(mAnimatorValue - &span class=&hljs-number& style=&color: rgb(0, 102, 102); box-sizing: border-&&0.5&/span&)) * mLength));
mPathMeasure.getSegment(start, stop, mDst, &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&true&/span&);
canvas.drawPath(mDst, mPaint);
}&/code&&ul class=&pre-numbering& style=&box-sizing: border- position: width: 50 top: 0 left: 0 margin: 0 padding: 6px 0px 40 border-right-width: 1 border-right-style: border-right-color: rgb(221, 221, 221); list-style: text-align: background-color: rgb(238, 238, 238);&&&li style=&box-sizing: border- padding: 0px 5&&1&/li&&li style=&box-sizing: border- padding: 0px 5&&2&/li&&li style=&box-sizing: border- padding: 0px 5&&3&/li&&li style=&box-sizing: border- padding: 0px 5&&4&/li&&li style=&box-sizing: border- padding: 0px 5&&5&/li&&li style=&box-sizing: border- padding: 0px 5&&6&/li&&li style=&box-sizing: border- padding: 0px 5&&7&/li&&li style=&box-sizing: border- padding: 0px 5&&8&/li&&li style=&box-sizing: border- padding: 0px 5&&9&/li&&li style=&box-sizing: border- padding: 0px 5&&10&/li&&li style=&box-sizing: border- padding: 0px 5&&11&/li&&/ul&&ul class=&pre-numbering& style=&box-sizing: border- position: width: 50 top: 0 left: 0 margin: 0 padding: 6px 0px 40 border-right-width: 1 border-right-style: border-right-color: rgb(221, 221, 221); list-style: text-align: background-color: rgb(238, 238, 238);&&&li style=&box-sizing: border- padding: 0px 5&&1&/li&&li style=&box-sizing: border- padding: 0px 5&&2&/li&&li style=&box-sizing: border- padding: 0px 5&&3&/li&&li style=&box-sizing: border- padding: 0px 5&&4&/li&&li style=&box-sizing: border- padding: 0px 5&&5&/li&&li style=&box-sizing: border- padding: 0px 5&&6&/li&&li style=&box-sizing: border- padding: 0px 5&&7&/li&&li style=&box-sizing: border- padding: 0px 5&&8&/li&&li style=&box-sizing: border- padding: 0px 5&&9&/li&&li style=&box-sizing: border- padding: 0px 5&&10&/li&&li style=&box-sizing: border- padding: 0px 5&&11&/li&&/ul&
路径绘制——另辟蹊径
关于路径绘制，View的始祖Romain Guy曾经有一篇文章讲解了一个很使用的技巧，地址如下所示：
Romain Guy使用DashPathEffect来实现了路径绘制。
&code class=&hljs cs has-numbering& style=&display: padding: 0 color: box-sizing: border- font-family: 'Source Code Pro',font-size: white-space: border-radius: 0 word-wrap: background:&&DashPathEffect(&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&float&/span&[] intervals, &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&float&/span& phase)&/code&&ul class=&pre-numbering& style=&box-sizing: border- position: width: 50 top: 0 left: 0 margin: 0 padding: 6px 0px 40 border-right-width: 1 border-right-style: border-right-color: rgb(221, 221, 221); list-style: text-align: background-color: rgb(238, 238, 238);&&&li style=&box-sizing: border- padding: 0px 5&&1&/li&&/ul&&ul class=&pre-numbering& style=&box-sizing: border- position: width: 50 top: 0 left: 0 margin: 0 padding: 6px 0px 40 border-right-width: 1 border-right-style: border-right-color: rgb(221, 221, 221); list-style: text-align: background-color: rgb(238, 238, 238);&&&li style=&box-sizing: border- padding: 0px 5&&1&/li&&/ul&
DashPathEffect传入了一个intervals数组，用来控制实线和虚线的数组的显示，那么当实线和虚线都是整个路径的长度时，整个路径就只显示实线或者虚线了，这时候通过第二个参数phase来控制起始偏移量，就可以完成整个路径的绘制了，这的确是一个非常trick而且有效的方式，效果如图所示：
代码如下所示：
&code class=&hljs java has-numbering& style=&display: padding: 0 color: box-sizing: border- font-family: 'Source Code Pro',font-size: white-space: border-radius: 0 word-wrap: background:&&&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&package&/span& .pathart.
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&import&/span& android.animation.ValueA
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&import&/span& android.content.C
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&import&/span& android.graphics.C
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&import&/span& android.graphics.C
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&import&/span& android.graphics.DashPathE
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&import&/span& android.graphics.P
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&import&/span& android.graphics.P
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&import&/span& android.graphics.PathE
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&import&/span& android.graphics.PathM
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&import&/span& android.util.AttributeS
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&import&/span& android.view.V
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&import&/span& android.view.animation.AccelerateDecelerateI
&span class=&hljs-javadoc& style=&color: rgb(136, 0, 0); box-sizing: border-&&/**
* 路径绘制——DashPathEffect
* Created by xuyisheng on 16/7/15.
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&public&/span& &span class=&hljs-class& style=&box-sizing: border-&&&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&class&/span& &span class=&hljs-title& style=&box-sizing: border- color: rgb(102, 0, 102);&&PathPainterEffect&/span& &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&extends&/span& &span class=&hljs-title& style=&box-sizing: border- color: rgb(102, 0, 102);&&View&/span& &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&implements&/span& &span class=&hljs-title& style=&box-sizing: border- color: rgb(102, 0, 102);&&View&/span&.&span class=&hljs-title& style=&box-sizing: border- color: rgb(102, 0, 102);&&OnClickListener&/span&{&/span&
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&private&/span& Paint mP
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&private&/span& Path mP
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&private&/span& PathMeasure mPathM
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&private&/span& PathEffect mE
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&private&/span& &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&float&/span& fraction = &span class=&hljs-number& style=&color: rgb(0, 102, 102); box-sizing: border-&&0&/span&;
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&private&/span& ValueAnimator mA
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&public&/span& &span class=&hljs-title& style=&box-sizing: border-&&PathPainterEffect&/span&(Context context) {
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&super&/span&(context);
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&public&/span& &span class=&hljs-title& style=&box-sizing: border-&&PathPainterEffect&/span&(Context context, AttributeSet attrs) {
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&super&/span&(context, attrs);
mPath = &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&new&/span& Path();
mPath.reset();
mPath.moveTo(&span class=&hljs-number& style=&color: rgb(0, 102, 102); box-sizing: border-&&100&/span&, &span class=&hljs-number& style=&color: rgb(0, 102, 102); box-sizing: border-&&100&/span&);
mPath.lineTo(&span class=&hljs-number& style=&color: rgb(0, 102, 102); box-sizing: border-&&100&/span&, &span class=&hljs-number& style=&color: rgb(0, 102, 102); box-sizing: border-&&500&/span&);
mPath.lineTo(&span class=&hljs-number& style=&color: rgb(0, 102, 102); box-sizing: border-&&400&/span&, &span class=&hljs-number& style=&color: rgb(0, 102, 102); box-sizing: border-&&300&/span&);
mPath.close();
mPaint = &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&new&/span& Paint();
mPaint.setColor(Color.BLACK);
mPaint.setStyle(Paint.Style.STROKE);
mPaint.setStrokeWidth(&span class=&hljs-number& style=&color: rgb(0, 102, 102); box-sizing: border-&&5&/span&);
mPathMeasure = &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&new&/span& PathMeasure(mPath, &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&false&/span&);
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&final&/span& &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&float&/span& length = mPathMeasure.getLength();
mAnimator = ValueAnimator.ofFloat(&span class=&hljs-number& style=&color: rgb(0, 102, 102); box-sizing: border-&&1&/span&, &span class=&hljs-number& style=&color: rgb(0, 102, 102); box-sizing: border-&&0&/span&);
mAnimator.setInterpolator(&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&new&/span& AccelerateDecelerateInterpolator());
mAnimator.setDuration(&span class=&hljs-number& style=&color: rgb(0, 102, 102); box-sizing: border-&&2000&/span&);
mAnimator.addUpdateListener(&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&new&/span& ValueAnimator.AnimatorUpdateListener() {
&span class=&hljs-annotation& style=&color: rgb(155, 133, 157); box-sizing: border-&&@Override&/span&
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&public&/span& &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&void&/span& &span class=&hljs-title& style=&box-sizing: border-&&onAnimationUpdate&/span&(ValueAnimator valueAnimator) {
fraction = (&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&float&/span&) valueAnimator.getAnimatedValue();
mEffect = &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&new&/span& DashPathEffect(&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&new&/span& &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&float&/span&[]{length, length}, fraction * length);
mPaint.setPathEffect(mEffect);
invalidate();
setOnClickListener(&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&this&/span&);
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&public&/span& &span class=&hljs-title& style=&box-sizing: border-&&PathPainterEffect&/span&(Context context, AttributeSet attrs, &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&int&/span& defStyleAttr) {
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&super&/span&(context, attrs, defStyleAttr);
&span class=&hljs-annotation& style=&color: rgb(155, 133, 157); box-sizing: border-&&@Override&/span&
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&protected&/span& &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&void&/span& &span class=&hljs-title& style=&box-sizing: border-&&onDraw&/span&(Canvas canvas) {
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&super&/span&.onDraw(canvas);
canvas.drawPath(mPath, mPaint);
&span class=&hljs-annotation& style=&color: rgb(155, 133, 157); box-sizing: border-&&@Override&/span&
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&public&/span& &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&void&/span& &span class=&hljs-title& style=&box-sizing: border-&&onClick&/span&(View view) {
mAnimator.start();
&/code&&ul class=&pre-numbering& style=&box-sizing: border- position: width: 50 top: 0 left: 0 margin: 0 padding: 6px 0px 40 border-right-width: 1 border-right-style: border-right-color: rgb(221, 221, 221); list-style: text-align: background-color: rgb(238, 238, 238);&&&li style=&box-sizing: border- padding: 0px 5&&1&/li&&li style=&box-sizing: border- padding: 0px 5&&2&/li&&li style=&box-sizing: border- padding: 0px 5&&3&/li&&li style=&box-sizing: border- padding: 0px 5&&4&/li&&li style=&box-sizing: border- padding: 0px 5&&5&/li&&li style=&box-sizing: border- padding: 0px 5&&6&/li&&li style=&box-sizing: border- padding: 0px 5&&7&/li&&li style=&box-sizing: border- padding: 0px 5&&8&/li&&li style=&box-sizing: border- padding: 0px 5&&9&/li&&li style=&box-sizing: border- padding: 0px 5&&10&/li&&li style=&box-sizing: border- padding: 0px 5&&11&/li&&li style=&box-sizing: border- padding: 0px 5&&12&/li&&li style=&box-sizing: border- padding: 0px 5&&13&/li&&li style=&box-sizing: border- padding: 0px 5&&14&/li&&li style=&box-sizing: border- padding: 0px 5&&15&/li&&li style=&box-sizing: border- padding: 0px 5&&16&/li&&li style=&box-sizing: border- padding: 0px 5&&17&/li&&li style=&box-sizing: border- padding: 0px 5&&18&/li&&li style=&box-sizing: border- padding: 0px 5&&19&/li&&li style=&box-sizing: border- padding: 0px 5&&20&/li&&li style=&box-sizing: border- padding: 0px 5&&21&/li&&li style=&box-sizing: border- padding: 0px 5&&22&/li&&li style=&box-sizing: border- padding: 0px 5&&23&/li&&li style=&box-sizing: border- padding: 0px 5&&24&/li&&li style=&box-sizing: border- padding: 0px 5&&25&/li&&li style=&box-sizing: border- padding: 0px 5&&26&/li&&li style=&box-sizing: border- padding: 0px 5&&27&/li&&li style=&box-sizing: border- padding: 0px 5&&28&/li&&li style=&box-sizing: border- padding: 0px 5&&29&/li&&li style=&box-sizing: border- padding: 0px 5&&30&/li&&li style=&box-sizing: border- padding: 0px 5&&31&/li&&li style=&box-sizing: border- padding: 0px 5&&32&/li&&li style=&box-sizing: border- padding: 0px 5&&33&/li&&li style=&box-sizing: border- padding: 0px 5&&34&/li&&li style=&box-sizing: border- padding: 0px 5&&35&/li&&li style=&box-sizing: border- padding: 0px 5&&36&/li&&li style=&box-sizing: border- padding: 0px 5&&37&/li&&li style=&box-sizing: border- padding: 0px 5&&38&/li&&li style=&box-sizing: border- padding: 0px 5&&39&/li&&li style=&box-sizing: border- padding: 0px 5&&40&/li&&li style=&box-sizing: border- padding: 0px 5&&41&/li&&li style=&box-sizing: border- padding: 0px 5&&42&/li&&li style=&box-sizing: border- padding: 0px 5&&43&/li&&li style=&box-sizing: border- padding: 0px 5&&44&/li&&li style=&box-sizing: border- padding: 0px 5&&45&/li&&li style=&box-sizing: border- padding: 0px 5&&46&/li&&li style=&box-sizing: border- padding: 0px 5&&47&/li&&li style=&box-sizing: border- padding: 0px 5&&48&/li&&li style=&box-sizing: border- padding: 0px 5&&49&/li&&li style=&box-sizing: border- padding: 0px 5&&50&/li&&li style=&box-sizing: border- padding: 0px 5&&51&/li&&li style=&box-sizing: border- padding: 0px 5&&52&/li&&li style=&box-sizing: border- padding: 0px 5&&53&/li&&li style=&box-sizing: border- padding: 0px 5&&54&/li&&li style=&box-sizing: border- padding: 0px 5&&55&/li&&li style=&box-sizing: border- padding: 0px 5&&56&/li&&li style=&box-sizing: border- padding: 0px 5&&57&/li&&li style=&box-sizing: border- padding: 0px 5&&58&/li&&li style=&box-sizing: border- padding: 0px 5&&59&/li&&li style=&box-sizing: border- padding: 0px 5&&60&/li&&li style=&box-sizing: border- padding: 0px 5&&61&/li&&li style=&box-sizing: border- padding: 0px 5&&62&/li&&li style=&box-sizing: border- padding: 0px 5&&63&/li&&li style=&box-sizing: border- padding: 0px 5&&64&/li&&li style=&box-sizing: border- padding: 0px 5&&65&/li&&li style=&box-sizing: border- padding: 0px 5&&66&/li&&li style=&box-sizing: border- padding: 0px 5&&67&/li&&li style=&box-sizing: border- padding: 0px 5&&68&/li&&li style=&box-sizing: border- padding: 0px 5&&69&/li&&li style=&box-sizing: border- padding: 0px 5&&70&/li&&li style=&box-sizing: border- padding: 0px 5&&71&/li&&li style=&box-sizing: border- padding: 0px 5&&72&/li&&li style=&box-sizing: border- padding: 0px 5&&73&/li&&li style=&box-sizing: border- padding: 0px 5&&74&/li&&li style=&box-sizing: border- padding: 0px 5&&75&/li&&li style=&box-sizing: border- padding: 0px 5&&76&/li&&li style=&box-sizing: border- padding: 0px 5&&77&/li&&li style=&box-sizing: border- padding: 0px 5&&78&/li&&li style=&box-sizing: border- padding: 0px 5&&79&/li&&li style=&box-sizing: border- padding: 0px 5&&80&/li&&li style=&box-sizing: border- padding: 0px 5&&81&/li&&/ul&&ul class=&pre-numbering& style=&box-sizing: border- position: width: 50 top: 0 left: 0 margin: 0 padding: 6px 0px 40 border-right-width: 1 border-right-style: border-right-color: rgb(221, 221, 221); list-style: text-align: background-color: rgb(238, 238, 238);&&&li style=&box-sizing: border- padding: 0px 5&&1&/li&&li style=&box-sizing: border- padding: 0px 5&&2&/li&&li style=&box-sizing: border- padding: 0px 5&&3&/li&&li style=&box-sizing: border- padding: 0px 5&&4&/li&&li style=&box-sizing: border- padding: 0px 5&&5&/li&&li style=&box-sizing: border- padding: 0px 5&&6&/li&&li style=&box-sizing: border- padding: 0px 5&&7&/li&&li style=&box-sizing: border- padding: 0px 5&&8&/li&&li style=&box-sizing: border- padding: 0px 5&&9&/li&&li style=&box-sizing: border- padding: 0px 5&&10&/li&&li style=&box-sizing: border- padding: 0px 5&&11&/li&&li style=&box-sizing: border- padding: 0px 5&&12&/li&&li style=&box-sizing: border- padding: 0px 5&&13&/li&&li style=&box-sizing: border- padding: 0px 5&&14&/li&&li style=&box-sizing: border- padding: 0px 5&&15&/li&&li style=&box-sizing: border- padding: 0px 5&&16&/li&&li style=&box-sizing: border- padding: 0px 5&&17&/li&&li style=&box-sizing: border- padding: 0px 5&&18&/li&&li style=&box-sizing: border- padding: 0px 5&&19&/li&&li style=&box-sizing: border- padding: 0px 5&&20&/li&&li style=&box-sizing: border- padding: 0px 5&&21&/li&&li style=&box-sizing: border- padding: 0px 5&&22&/li&&li style=&box-sizing: border- padding: 0px 5&&23&/li&&li style=&box-sizing: border- padding: 0px 5&&24&/li&&li style=&box-sizing: border- padding: 0px 5&&25&/li&&li style=&box-sizing: border- padding: 0px 5&&26&/li&&li style=&box-sizing: border- padding: 0px 5&&27&/li&&li style=&box-sizing: border- padding: 0px 5&&28&/li&&li style=&box-sizing: border- padding: 0px 5&&29&/li&&li style=&box-sizing: border- padding: 0px 5&&30&/li&&li style=&box-sizing: border- padding: 0px 5&&31&/li&&li style=&box-sizing: border- padding: 0px 5&&32&/li&&li style=&box-sizing: border- padding: 0px 5&&33&/li&&li style=&box-sizing: border- padding: 0px 5&&34&/li&&li style=&box-sizing: border- padding: 0px 5&&35&/li&&li style=&box-sizing: border- padding: 0px 5&&36&/li&&li style=&box-sizing: border- padding: 0px 5&&37&/li&&li style=&box-sizing: border- padding: 0px 5&&38&/li&&li style=&box-sizing: border- padding: 0px 5&&39&/li&&li style=&box-sizing: border- padding: 0px 5&&40&/li&&li style=&box-sizing: border- padding: 0px 5&&41&/li&&li style=&box-sizing: border- padding: 0px 5&&42&/li&&li style=&box-sizing: border- padding: 0px 5&&43&/li&&li style=&box-sizing: border- padding: 0px 5&&44&/li&&li style=&box-sizing: border- padding: 0px 5&&45&/li&&li style=&box-sizing: border- padding: 0px 5&&46&/li&&li style=&box-sizing: border- padding: 0px 5&&47&/li&&li style=&box-sizing: border- padding: 0px 5&&48&/li&&li style=&box-sizing: border- padding: 0px 5&&49&/li&&li style=&box-sizing: border- padding: 0px 5&&50&/li&&li style=&box-sizing: border- padding: 0px 5&&51&/li&&li style=&box-sizing: border- padding: 0px 5&&52&/li&&li style=&box-sizing: border- padding: 0px 5&&53&/li&&li style=&box-sizing: border- padding: 0px 5&&54&/li&&li style=&box-sizing: border- padding: 0px 5&&55&/li&&li style=&box-sizing: border- padding: 0px 5&&56&/li&&li style=&box-sizing: border- padding: 0px 5&&57&/li&&li style=&box-sizing: border- padding: 0px 5&&58&/li&&li style=&box-sizing: border- padding: 0px 5&&59&/li&&li style=&box-sizing: border- padding: 0px 5&&60&/li&&li style=&box-sizing: border- padding: 0px 5&&61&/li&&li style=&box-sizing: border- padding: 0px 5&&62&/li&&li style=&box-sizing: border- padding: 0px 5&&63&/li&&li style=&box-sizing: border- padding: 0px 5&&64&/li&&li style=&box-sizing: border- padding: 0px 5&&65&/li&&li style=&box-sizing: border- padding: 0px 5&&66&/li&&li style=&box-sizing: border- padding: 0px 5&&67&/li&&li style=&box-sizing: border- padding: 0px 5&&68&/li&&li style=&box-sizing: border- padding: 0px 5&&69&/li&&li style=&box-sizing: border- padding: 0px 5&&70&/li&&li style=&box-sizing: border- padding: 0px 5&&71&/li&&li style=&box-sizing: border- padding: 0px 5&&72&/li&&li style=&box-sizing: border- padding: 0px 5&&73&/li&&li style=&box-sizing: border- padding: 0px 5&&74&/li&&li style=&box-sizing: border- padding: 0px 5&&75&/li&&li style=&box-sizing: border- padding: 0px 5&&76&/li&&li style=&box-sizing: border- padding: 0px 5&&77&/li&&li style=&box-sizing: border- padding: 0px 5&&78&/li&&li style=&box-sizing: border- padding: 0px 5&&79&/li&&li style=&box-sizing: border- padding: 0px 5&&80&/li&&li style=&box-sizing: border- padding: 0px 5&&81&/li&&/ul&
其关键代码就是在于设置：
&code class=&hljs glsl has-numbering& style=&display: padding: 0 color: box-sizing: border- font-family: 'Source Code Pro',font-size: white-space: border-radius: 0 word-wrap: background:&&mEffect = new DashPathEffect(new &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&float&/span&[]{&span class=&hljs-built_in& style=&color: rgb(102, 0, 102); box-sizing: border-&&length&/span&, &span class=&hljs-built_in& style=&color: rgb(102, 0, 102); box-sizing: border-&&length&/span&}, fraction * &span class=&hljs-built_in& style=&color: rgb(102, 0, 102); box-sizing: border-&&length&/span&);&/code&&ul class=&pre-numbering& style=&box-sizing: border- position: width: 50 top: 0 left: 0 margin: 0 padding: 6px 0px 40 border-right-width: 1 border-right-style: border-right-color: rgb(221, 221, 221); list-style: text-align: background-color: rgb(238, 238, 238);&&&li style=&box-sizing: border- padding: 0px 5&&1&/li&&/ul&&ul class=&pre-numbering& style=&box-sizing: border- position: width: 50 top: 0 left: 0 margin: 0 padding: 6px 0px 40 border-right-width: 1 border-right-style: border-right-color: rgb(221, 221, 221); list-style: text-align: background-color: rgb(238, 238, 238);&&&li style=&box-sizing: border- padding: 0px 5&&1&/li&&/ul&
后面通过属性动画来控制路径绘制即可。
坐标与切线
PathMeasure的getPosTan()方法，可以获取路径上的坐标点和对应点的切线坐标，其中，路径上对应的点非常好理解，就是对应的点的坐标，而另一个参数tan[]数组，它用于返回当前点的运动轨迹的斜率，要理解这个API，我们首先来看下Math中的atan2这个方法：
&code class=&hljs cs has-numbering& style=&display: padding: 0 color: box-sizing: border- font-family: 'Source Code Pro',font-size: white-space: border-radius: 0 word-wrap: background:&&&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&public&/span& &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&static&/span& &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&double&/span& &span class=&hljs-title& style=&box-sizing: border-&&atan2&/span& (&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&double&/span& y, &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&double&/span& x)&/code&&ul class=&pre-numbering& style=&box-sizing: border- position: width: 50 top: 0 left: 0 margin: 0 padding: 6px 0px 40 border-right-width: 1 border-right-style: border-right-color: rgb(221, 221, 221); list-style: text-align: background-color: rgb(238, 238, 238);&&&li style=&box-sizing: border- padding: 0px 5&&1&/li&&/ul&&ul class=&pre-numbering& style=&box-sizing: border- position: width: 50 top: 0 left: 0 margin: 0 padding: 6px 0px 40 border-right-width: 1 border-right-style: border-right-color: rgb(221, 221, 221); list-style: text-align: background-color: rgb(238, 238, 238);&&&li style=&box-sizing: border- padding: 0px 5&&1&/li&&/ul&
虽然atan()方法可以用于求一个反正切值，但是他传入的是一个角度，所以我们使用atan2()方法：
Math.atan2()函数返回点(x,y)和原点(0,0)之间直线的倾斜角
那么如何计算任意两点间直线的倾斜角呢?只需要将两点x,y坐标分别相减得到一个新的点(x2-x1,y2-y1)。然后利用它求出角度即可——Math.atan2(y2-y1,x2-x1)。
利用这个API，通常可以获取Path上的点坐标和点的运动趋势，对于运动趋势，通常通过Math.atan2()来转换为切线的角度，代码如下所示：
&code class=&hljs java has-numbering& style=&display: padding: 0 color: box-sizing: border- font-family: 'Source Code Pro',font-size: white-space: border-radius: 0 word-wrap: background:&&&span class=&hljs-annotation& style=&color: rgb(155, 133, 157); box-sizing: border-&&@Override&/span&
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&protected&/span& &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&void&/span& &span class=&hljs-title& style=&box-sizing: border-&&onDraw&/span&(Canvas canvas) {
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&super&/span&.onDraw(canvas);
mMeasure.getPosTan(mMeasure.getLength() * currentValue, pos, tan);
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&float&/span& degrees = (&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&float&/span&) (Math.atan2(tan[&span class=&hljs-number& style=&color: rgb(0, 102, 102); box-sizing: border-&&1&/span&], tan[&span class=&hljs-number& style=&color: rgb(0, 102, 102); box-sizing: border-&&0&/span&]) * &span class=&hljs-number& style=&color: rgb(0, 102, 102); box-sizing: border-&&180.0&/span& / Math.PI);
}&/code&&ul class=&pre-numbering& style=&box-sizing: border- position: width: 50 top: 0 left: 0 margin: 0 padding: 6px 0px 40 border-right-width: 1 border-right-style: border-right-color: rgb(221, 221, 221); list-style: text-align: background-color: rgb(238, 238, 238);&&&li style=&box-sizing: border- padding: 0px 5&&1&/li&&li style=&box-sizing: border- padding: 0px 5&&2&/li&&li style=&box-sizing: border- padding: 0px 5&&3&/li&&li style=&box-sizing: border- padding: 0px 5&&4&/li&&li style=&box-sizing: border- padding: 0px 5&&5&/li&&li style=&box-sizing: border- padding: 0px 5&&6&/li&&/ul&&ul class=&pre-numbering& style=&box-sizing: border- position: width: 50 top: 0 left: 0 margin: 0 padding: 6px 0px 40 border-right-width: 1 border-right-style: border-right-color: rgb(221, 221, 221); list-style: text-align: background-color: rgb(238, 238, 238);&&&li style=&box-sizing: border- padding: 0px 5&&1&/li&&li style=&box-sizing: border- padding: 0px 5&&2&/li&&li style=&box-sizing: border- padding: 0px 5&&3&/li&&li style=&box-sizing: border- padding: 0px 5&&4&/li&&li style=&box-sizing: border- padding: 0px 5&&5&/li&&li style=&box-sizing: border- padding: 0px 5&&6&/li&&/ul&
根据这个API，我们可以模拟一个圆上的点和点的运动趋势，代码如下：
&code class=&hljs java has-numbering& style=&display: padding: 0 color: box-sizing: border- font-family: 'Source Code Pro',font-size: white-space: border-radius: 0 word-wrap: background:&&&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&package&/span& .pathart.
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&import&/span& android.animation.ValueA
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&import&/span& android.content.C
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&import&/span& android.graphics.C
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&import&/span& android.graphics.P
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&import&/span& android.graphics.P
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&import&/span& android.graphics.PathM
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&import&/span& android.util.AttributeS
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&import&/span& android.view.V
&span class=&hljs-javadoc& style=&color: rgb(136, 0, 0); box-sizing: border-&&/**
* 曲线上切点
* Created by xuyisheng on 16/7/15.
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&public&/span& &span class=&hljs-class& style=&box-sizing: border-&&&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&class&/span& &span class=&hljs-title& style=&box-sizing: border- color: rgb(102, 0, 102);&&PathTan&/span& &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&extends&/span& &span class=&hljs-title& style=&box-sizing: border- color: rgb(102, 0, 102);&&View&/span& &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&implements&/span& &span class=&hljs-title& style=&box-sizing: border- color: rgb(102, 0, 102);&&View&/span&.&span class=&hljs-title& style=&box-sizing: border- color: rgb(102, 0, 102);&&OnClickListener&/span& {&/span&
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&private&/span& Path mP
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&private&/span& &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&float&/span&[]
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&private&/span& &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&float&/span&[]
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&private&/span& Paint mP
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&float&/span& currentValue = &span class=&hljs-number& style=&color: rgb(0, 102, 102); box-sizing: border-&&0&/span&;
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&private&/span& PathMeasure mM
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&public&/span& &span class=&hljs-title& style=&box-sizing: border-&&PathTan&/span&(Context context) {
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&super&/span&(context);
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&public&/span& &span class=&hljs-title& style=&box-sizing: border-&&PathTan&/span&(Context context, AttributeSet attrs) {
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&super&/span&(context, attrs);
mPath = &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&new&/span& Path();
mPaint = &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&new&/span& Paint();
mPaint.setStyle(Paint.Style.STROKE);
mPaint.setStrokeWidth(&span class=&hljs-number& style=&color: rgb(0, 102, 102); box-sizing: border-&&4&/span&);
mMeasure = &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&new&/span& PathMeasure();
mPath.addCircle(&span class=&hljs-number& style=&color: rgb(0, 102, 102); box-sizing: border-&&0&/span&, &span class=&hljs-number& style=&color: rgb(0, 102, 102); box-sizing: border-&&0&/span&, &span class=&hljs-number& style=&color: rgb(0, 102, 102); box-sizing: border-&&200&/span&, Path.Direction.CW);
mMeasure.setPath(mPath, &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&false&/span&);
pos = &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&new&/span& &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&float&/span&[&span class=&hljs-number& style=&color: rgb(0, 102, 102); box-sizing: border-&&2&/span&];
tan = &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&new&/span& &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&float&/span&[&span class=&hljs-number& style=&color: rgb(0, 102, 102); box-sizing: border-&&2&/span&];
setOnClickListener(&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&this&/span&);
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&public&/span& &span class=&hljs-title& style=&box-sizing: border-&&PathTan&/span&(Context context, AttributeSet attrs, &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&int&/span& defStyleAttr) {
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&super&/span&(context, attrs, defStyleAttr);
&span class=&hljs-annotation& style=&color: rgb(155, 133, 157); box-sizing: border-&&@Override&/span&
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&protected&/span& &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&void&/span& &span class=&hljs-title& style=&box-sizing: border-&&onDraw&/span&(Canvas canvas) {
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&super&/span&.onDraw(canvas);
mMeasure.getPosTan(mMeasure.getLength() * currentValue, pos, tan);
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&float&/span& degrees = (&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&float&/span&) (Math.atan2(tan[&span class=&hljs-number& style=&color: rgb(0, 102, 102); box-sizing: border-&&1&/span&], tan[&span class=&hljs-number& style=&color: rgb(0, 102, 102); box-sizing: border-&&0&/span&]) * &span class=&hljs-number& style=&color: rgb(0, 102, 102); box-sizing: border-&&180.0&/span& / Math.PI);
canvas.save();
canvas.translate(&span class=&hljs-number& style=&color: rgb(0, 102, 102); box-sizing: border-&&400&/span&, &span class=&hljs-number& style=&color: rgb(0, 102, 102); box-sizing: border-&&400&/span&);
canvas.drawPath(mPath, mPaint);
canvas.drawCircle(pos[&span class=&hljs-number& style=&color: rgb(0, 102, 102); box-sizing: border-&&0&/span&], pos[&span class=&hljs-number& style=&color: rgb(0, 102, 102); box-sizing: border-&&1&/span&], &span class=&hljs-number& style=&color: rgb(0, 102, 102); box-sizing: border-&&10&/span&, mPaint);
canvas.rotate(degrees);
canvas.drawLine(&span class=&hljs-number& style=&color: rgb(0, 102, 102); box-sizing: border-&&0&/span&, -&span class=&hljs-number& style=&color: rgb(0, 102, 102); box-sizing: border-&&200&/span&, &span class=&hljs-number& style=&color: rgb(0, 102, 102); box-sizing: border-&&300&/span&, -&span class=&hljs-number& style=&color: rgb(0, 102, 102); box-sizing: border-&&200&/span&, mPaint);
canvas.restore();
&span class=&hljs-annotation& style=&color: rgb(155, 133, 157); box-sizing: border-&&@Override&/span&
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&public&/span& &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&void&/span& &span class=&hljs-title& style=&box-sizing: border-&&onClick&/span&(View view) {
ValueAnimator animator = ValueAnimator.ofFloat(&span class=&hljs-number& style=&color: rgb(0, 102, 102); box-sizing: border-&&0&/span&, &span class=&hljs-number& style=&color: rgb(0, 102, 102); box-sizing: border-&&1&/span&);
animator.addUpdateListener(&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&new&/span& ValueAnimator.AnimatorUpdateListener() {
&span class=&hljs-annotation& style=&color: rgb(155, 133, 157); box-sizing: border-&&@Override&/span&
&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&public&/span& &span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&void&/span& &span class=&hljs-title& style=&box-sizing: border-&&onAnimationUpdate&/span&(ValueAnimator valueAnimator) {
currentValue = (&span class=&hljs-keyword& style=&color: rgb(0, 0, 136); box-sizing: border-&&float&/span&) valueAnimator.getAnimatedValue();
invalidate();
animator.setDuration(&span class=&hljs-number& style=&color: rgb(0, 102, 102); box-sizing: border-&&3000&/span&);
animator.setRepeatCount(ValueAnimator.INFINITE);
animator.start();
&/code&&ul class=&pre-numbering& style=&box-sizing: border- position: width: 50 top: 0 left: 0 margin: 0 padding: 6px 0px 40 border-right-width: 1 border-right-style: border-right-color: rgb(221, 221, 221); list-style: text-align: background-color: rgb(238, 238, 238);&&&li style=&box-sizing: border- padding: 0px 5&&1&/li&&li style=&box-sizing: border- padding: 0px 5&&2&/li&&li style=&box-sizing: border- padding: 0px 5&&3&/li&&li style=&box-sizing: border- padding: 0px 5&&4&/li&&li style=&box-sizing: border- padding: 0px 5&&5&/li&&li style=&box-sizing: border- padding: 0px 5&&6&/li&&li style=&box-sizing: border- padding: 0px 5&&7&/li&&li style=&box-sizing: border- padding: 0px 5&&8&/li&&li style=&box-sizing: border- padding: 0px 5&&9&/li&&li style=&box-sizing: border- padding: 0px 5&&10&/li&&li style=&box-sizing: border- padding: 0px 5&&11&/li&&li style=&box-sizing: border- padding: 0px 5&&12&/li&&li style=&box-sizing: border- padding: 0px 5&&13&/li&&li style=&box-sizing: border- padding: 0px 5&&14&/li&&li style=&box-sizing: border- padding: 0px 5&&15&/li&&li style=&box-sizing: border- padding: 0px 5&&16&/li&&li style=&box-sizing: border- padding: 0px 5&&17&/li&&li style=&box-sizing: border- padding: 0px 5&&18&/li&&li style=&box-sizing: border- padding: 0px 5&&19&/li&&li style=&box-sizing: border- padding: 0px 5&&20&/li&&li style=&box-sizing: border- padding: 0px 5&&21&/li&&li style=&box-sizing: border- padding: 0px 5&&22&/li&&li style=&box-sizing: border- padding: 0px 5&&23&/li&&li style=&box-sizing: border- padding: 0px 5&&24&/li&&li style=&box-sizing: border- padding: 0px 5&&25&/li&&li style=&box-sizing: border- padding: 0px 5&&26&/li&&li style=&box-sizing: border- padding: 0px 5&&27&/li&&li style=&box-sizing: border- padding: 0px 5&&28&/li&&li style=&box-sizing: border- padding: 0px 5&&29&/li&&li style=&box-sizing: border- padding: 0px 5&&30&/li&&li style=&box-sizing: border- padding: 0px 5&&31&/li&&li style=&box-sizing: border- padding: 0px 5&&32&/li&&li style=&box-sizing: border- padding: 0px 5&&33&/li&&li style=&box-sizing: border- padding: 0px 5&&34&/li&&li style=&box-sizing: border- padding: 0px 5&&35&/li&&li style=&box-sizing: border- padding: 0px 5&&36&/li&&li style=&box-sizing: border- padding: 0px 5&&37&/li&&li style=&box-sizing: border- padding: 0px 5&&38&/li&&li style=&box-sizing: border- padding: 0px 5&&39&/li&&li style=&box-sizing: border- padding: 0px 5&&40&/li&&li style=&box-sizing: border- padding: 0px 5&&41&/li&&li style=&box-sizing: border- padding: 0px 5&&42&/li&&li style=&box-sizing: border- padding: 0px 5&&43&/li&&li style=&box-sizing: border- padding: 0px 5&&44&/li&&li style=&box-sizing: border- padding: 0px 5&&45&/li&&li style=&box-sizing: border- padding: 0px 5&&46&/li&&li style=&box-sizing: border- padding: 0px 5&&47&/li&&li style=&box-sizing: border- padding: 0px 5&&48&/li&&li style=&box-sizing: border- padding: 0px 5&&49&/li&&li style=&box-sizing: border- padding: 0px 5&&50&/li&&li style=&box-sizing: border- padding: 0px 5&&51&/li&&li style=&box-sizing: border- padding: 0px 5&&52&/li&&li style=&box-sizing: border- padding: 0px 5&&53&/li&&li style=&box-sizing: border- padding: 0px 5&&54&/li&&li style=&box-sizing: border- padding: 0px 5&&55&/li&&li style=&box-sizing: border- padding: 0px 5&&56&/li&&li style=&box-sizing: border- padding: 0px 5&&57&/li&&li style=&box-sizing: border- padding: 0px 5&&58&/li&&li style=&box-sizing: border- padding: 0px 5&&59&/li&&li style=&box-sizing: border- padding: 0px 5&&60&/li&&li style=&box-sizing: border- padding: 0px 5&&61&/li&&li style=&box-sizing: border- padding: 0px 5&&62&/li&&li style=&box-sizing: border- padding: 0px 5&&63&/li&&li style=&box-sizing: border- padding: 0px 5&&64&/li&&li style=&box-sizing: border- padding: 0px 5&&65&/li&&li style=&box-sizing: border- padding: 0px 5&&66&/li&&li style=&box-sizing: border- padding: 0px 5&&67&/li&&li style=&box-sizing: border- padding: 0px 5&&68&/li&&li style=&box-sizing: border- padding: 0px 5&&69&/li&&li style=&box-sizing: border- padding: 0px 5&&70&/li&&li style=&box-sizing: border- padding: 0px 5&&71&/li&&li style=&box-sizing: border- padding: 0px 5&&72&/li&&li style=&box-sizing: border- padding: 0px 5&&73&/li&&li style=&box-sizing: border- padding: 0px 5&&74&/li&&li style=&box-sizing: border- padding: 0px 5&&75&/li&&li style=&box-sizing: border- padding: 0px 5&&76&/li&&li style=&box-sizing: border- padding: 0px 5&&77&/li&&li style=&box-sizing: border- padding: 0px 5&&78&/li&&/ul&&ul class=&pre-numbering& style=&box-sizing: border- position: width: 50 top: 0 left: 0 margin: 0 padding: 6px 0px 40 border-right-width: 1 border-right-style: border-right-color: rgb(221, 221, 221); list-style: text-align: background-color: rgb(238, 238, 238);&&&li style=&box-sizing: border- padding: 0px 5&&1&/li&&li style=&box-sizing: border- padding: 0px 5&&2&/li&&li style=&box-sizing: border- padding: 0px 5&&3&/li&&li style=&box-sizing: border- padding: 0px 5&&4&/li&&li style=&box-sizing: border- padding: 0px 5&&5&/li&&li style=&box-sizing: border- padding: 0px 5&&6&/li&&li style=&box-sizing: border- padding: 0px 5&&7&/li&&li style=&box-sizing: border- padding: 0px 5&&8&/li&&li style=&box-sizing: border- padding: 0px 5&&9&/li&&li style=&box-sizing: border- padding: 0px 5&&10&/li&&li style=&box-sizing: border- padding: 0px 5&&11&/li&&li style=&box-sizing: border- padding: 0px 5&&12&/li&&li style=&box-sizing: border- padding: 0px 5&&13&/li&&li style=&box-sizing: border- padding: 0px 5&&14&/li&&li style=&box-sizing: border- padding: 0px 5&&15&/li&&li style=&box-sizing: border- padding: 0px 5&&16&/li&&li style=&box-sizing: border- padding: 0px 5&&17&/li&&li style=&box-sizing: border- padding: 0px 5&&18&/li&&li style=&box-sizing: border- padding: 0px 5&&19&/li&&li style=&box-sizing: border- padding: 0px 5&&20&/li&&li style=&box-sizing: border- padding: 0px 5&&21&/li&&li style=&box-sizing: border- padding: 0px 5&&22&/li&&li style=&box-sizing: border- padding: 0px 5&&23&/li&&li style=&box-sizing: border- padding: 0px 5&&24&/li&&li style=&box-sizing: border- padding: 0px 5&&25&/li&&li style=&box-sizing: border- padding: 0px 5&&26&/li&&li style=&box-sizing: border- padding: 0px 5&&27&/li&&li style=&box-sizing: border- padding: 0px 5&&28&/li&&li style=&box-sizing: border- padding: 0px 5&&29&/li&&li style=&box-sizing: border- padding: 0px 5&&30&/li&&li style=&box-sizing: border- padding: 0px 5&&31&/li&&li style=&box-sizing: border- padding: 0px 5&&32&/li&&li style=&box-sizing: border- padding: 0px 5&&33&/li&&li style=&box-sizing: border- padding: 0px 5&&34&/li&&li style=&box-sizing: border- padding: 0px 5&&35&/li&&li style=&box-sizing: border- padding: 0px 5&&36&/li&&li style=&box-sizing: border- padding: 0px 5&&37&/li&&li style=&box-sizing: border- padding: 0px 5&&38&/li&&li style=&box-sizing: border- padding: 0px 5&&39&/li&&li style=&box-sizing: border- padding: 0px 5&&40&/li&&li style=&box-sizing: border- padding: 0px 5&&41&/li&&li style=&box-sizing: border- padding: 0px 5&&42&/li&&li style=&box-sizing: border- padding: 0px 5&&43&/li&&li style=&box-sizing: border- padding: 0px 5&&44&/li&&li style=&box-sizing: border- padding: 0px 5&&45&/li&&li style=&box-sizing: border- padding: 0px 5&&46&/li&&li style=&box-sizing: border- padding: 0px 5&&47&/li&&li style=&box-sizing: border- padding: 0px 5&&48&/li&&li style=&box-sizing: border- padding: 0px 5&&49&/li&&li style=&box-sizing: border- padding: 0px 5&&50&/li&&li style=&box-sizing: border- padding: 0px 5&&51&/li&&li style=&box-sizing: border- padding: 0px 5&&52&/li&&li style=&box-sizing: border- padding: 0px 5&&53&/li&&li style=&box-sizing: border- padding: 0px 5&&54&/li&&li style=&box-sizing: border- padding: 0px 5&&55&/li&&li style=&box-sizing: border- padding: 0px 5&&56&/li&&li style=&box-sizing: border- padding: 0px 5&&57&/li&&li style=&box-sizing: border- padding: 0px 5&&58&/li&&li style=&box-sizing: border- padding: 0px 5&&59&/li&&li style=&box-sizing: border- padding: 0px 5&&60&/li&&li style=&box-sizing: border- padding: 0px 5&&61&/li&&li style=&box-sizing: border- padding: 0px 5&&62&/li&&li style=&box-sizing: border- padding: 0px 5&&63&/li&&li style=&box-sizing: border- padding: 0px 5&&64&/li&&li style=&box-sizing: border- padding: 0px 5&&65&/li&&li style=&box-sizing: border- padding: 0px 5&&66&/li&&li style=&box-sizing: border- padding: 0px 5&&67&/li&&li style=&box-sizing: border- padding: 0px 5&&68&/li&&li style=&box-sizing: border- padding: 0px 5&&69&/li&&li style=&box-sizing: border- padding: 0px 5&&70&/li&&li style=&box-sizing: border- padding: 0px 5&&71&/li&&li style=&box-sizing: border- padding: 0px 5&&72&/li&&li style=&box-sizing: border- padding: 0px 5&&73&/li&&li style=&box-sizing: border- padding: 0px 5&&74&/li&&li style=&box-sizing: border- padding: 0px 5&&75&/li&&li style=&box-sizing: border- padding: 0px 5&&76&/li&&li style=&box-sizing: border- padding: 0px 5&&77&/li&&li style=&box-sizing: border- padding: 0px 5&&78&/li&&/ul&
Demo效果如图所示：
只不过这里在绘制的时候，使用了一些Trick，先通过canvas.translate方法将原点移动的圆心，同时，通过canvas.rotate将运动趋势的角度转换为画布的旋转，这样每次绘制切线，就只需要画一条同样的切线即可。
阅读排行榜}
我要回帖
更多关于 方舟生存进化显卡崩溃 的文章
更多推荐
- ·听说跃安门窗品牌的十大排名的产品销量如何？是否容易销售？
- ·中*电信天翼网盘下载限速吗云盘限速吗？
- ·想要彻底清洁隐形纱窗，是否需要使用戴森吸尘器清洗拆解，有哪些注意事项？
- ·oppo reno颜色11 曜石黑适合女生吗？
- ·oppo手机恢复旧版系统怎样恢复coloros
- ·政策百科我2017年农村房屋新政策三级残，房屋倒十多年，无能力修现在都没房住，现年也六十四岁了，该怎么办？
- ·苹果6p听歌老是自动停韩版插上耳机听歌有哧拉哧啦的噪音特别大，耳机插在6s上没有问
- ·pptv电视机哪里生产的，真的那么差吗？
- ·王者荣耀战区排名怎么改荣耀战区，别复制粘贴
- ·求动漫生肉动漫在线观看地址，我做MAD，需要很多生肉动漫在线观看素材，不知道有国内网页或贴吧什么的没，外文的话，下载太慢。
- ·今日头条自动评论软件里买了手表，发现网络评论都说是假货，货到付款，手表还没寄到，我怎么拒收？
- ·电脑插上雷蛇鼠标左键失灵就死机键鼠失灵怎么回事
- ·哎呦喂，我用手机下载了一个王牌御史电影下载，但是运行不了，是不是我下错版本了啊？怎么回事
- ·隆基泰和 点评的网站征婚上哪个网站
- ·我要微信装b小视频制作软件件
- ·你好，请问如何加微信公众号推送乱码号是一堆乱码的好友
- ·微信小程序 汉字乱码是一堆乱码怎么加好友
- ·现在微商怎么百度推广有效果么，求大神指教互相进步！？
- ·我的网贷不查征信的网贷上评分怎么那么低
- ·换手机了,微信忘密码了号码丢了怎么找回微信
- ·1050显卡 8G内存 可以玩方舟生存进化烧显卡么
- ·1050什么显卡能玩方舟 8G内存可以玩方舟么
- ·求海贼王系列cg第一期cg图很多期对吗，求大神了，1303789804，可以用钱买也可以，麻烦
- ·winrar怎么修复压缩包镜像包
- ·哇塞，我用MuMu电脑模拟器玩王者荣耀在电脑上玩的王牌御史，居然还有抽奖的活动的嘞，厉害了厉害了，哈哈，
- ·我在来分期买了一台华为p10值得买吗，到货了结果发现是别人用过的，是一台二手手机，可我下单的是全新手机，请
- ·微信分享链接打开app的视频链接打开总是进入下载优酷app界面怎么回事
- ·卖手机号码的网站丢了怎么找回
- ·百度云同步盘登陆不上版登陆155010
- ·新款华硕fx53v做系统f7700系统崩溃怎办?
- ·求美人为陷第一季免费三季的百度云链接，谢谢各位
- ·显卡1050 4G独显 内存8G能玩方舟显卡要求生存进化么
- ·wpsoffice 关联文件文件wpsoffice 关联文件文件密码忘了
- ·百度知道私密问答怎么在私密问答或者悬赏问答上提问问题
- ·听我男朋友说王牌御史电影挺好玩的，于是我就用MuMu模拟器在电脑上下载了这个游戏，但是我想问一下这
- ·谁给我求一个不要的微信号微信号
