Android基础入门教程——8.3.17 Canvas API详解(Part 2)剪切方法合集

http://blog.csdn.net/coder_pig/article/details/49779565

本节引言：

本节继续带来Android绘图系列详解之Canvas API详解(Part 2)，今天要讲解的是Canvas

中的ClipXxx方法族！我们可以看到文档中给我们提供的Clip方法有三种类型：

clipPath( )，clipRect( )，clipRegion( )；

通过Path，Rect，Region的不同组合，几乎可以支持任意形状的裁剪区域！

Path：可以是开放或闭合的曲线，线构成的复杂的集合图形

Rect：矩形区域

Region：可以理解为区域组合，比如可以将两个区域相加，相减，并，疑惑等！

Region.Op定义了Region支持的区域间运算种类！等下我们会讲到，

另外要说一点，我们平时理解的剪切可能是对已经存在的图形进行Clip，但是Android中对

Canvas进行Clip，是要在画图前进行的，如果画图后再对Canvas进行Clip的话将不会影响

到已经画好的图形，记住Clip是针对Canvas而非图形！

嗯，不BB，直接开始本节内容！

官方API文档：Canvas

1.Region.Op组合方式详解

其实难点无非这个，Region代表着区域，表示的是Canvas图层上的某一块封闭区域！

当然，有时间你可以自己慢慢去扣这个类，而我们一般关注的只是他的一个枚举值：Op



下面我们来看看个个枚举值所起的作用：

我们假设两个裁剪区域A和B，那么我们调用Region.Op对应的枚举值：

DIFFERENCE：A和B的差集范围，即A - B，只有在此范围内的绘制内容才会被显示；

INTERSECT：即A和B的交集范围，只有在此范围内的绘制内容才会被显示

UNION：即A和B的并集范围，即两者所包括的范围的绘制内容都会被显示；

XOR：A和B的补集范围，此例中即A除去B以外的范围，只有在此范围内的绘制内容才会被显示；

REVERSE_DIFFERENCE：B和A的差集范围，即B - A，只有在此范围内的绘制内容才会被显示；

REPLACE：不论A和B的集合状况，B的范围将全部进行显示，如果和A有交集，则将覆盖A的交集范围；

如果你学过集合，那么画个Venn(韦恩图)就一清二楚了，没学过？没事，我们写个例子来试试

对应的结果~！写个初始化画笔以及画矩形的方法:

<code class="language-Java hljs cs has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">    <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">init</span>() {
mPaint = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> Paint();
mPaint.setAntiAlias(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">true</span>);
mPaint.setStrokeWidth(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">6</span>);
mPaint.setColor(getResources().getColor(R.color.blush));
}

<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">drawScene</span>(Canvas canvas){
canvas.drawRect(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">200</span>, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">200</span>, mPaint);
}</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li></ul>

Op.DIFFERENCE：

<code class="language-Java hljs mel has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">canvas</span>.clipRect(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">10</span>, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">10</span>, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">110</span>, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">110</span>);        <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//第一个</span>
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">canvas</span>.clipRect(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">50</span>, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">50</span>, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">150</span>, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">150</span>, Region.Op.DIFFERENCE); <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//第二个</span>
drawScene(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">canvas</span>);</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li></ul>

结果：



先后在(10,10)以及(50,50)为起点，裁剪了两个100*100的矩形，得出的裁剪结果是：

A和B的差集 = A - (A和B相交的部分)

Op.INTERSECT：

<code class="language-Java hljs mel has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">canvas</span>.clipRect(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">10</span>, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">10</span>, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">110</span>, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">110</span>);        <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//第一个</span>
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">canvas</span>.clipRect(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">50</span>, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">50</span>, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">150</span>, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">150</span>, Region.Op.INTERSECT); <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//第二个</span>
drawScene(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">canvas</span>);</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li></ul>

结果：



先后在(10,10)以及(50,50)为起点，裁剪了两个100*100的矩形，得出的裁剪结果是：

A和B的交集 = A和B相交的部分

Op.UNION：

<code class="language-Java hljs mel has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">canvas</span>.clipRect(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">10</span>, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">10</span>, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">110</span>, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">110</span>);        <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//第一个</span>
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">canvas</span>.clipRect(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">40</span>, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">40</span>, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">140</span>, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">140</span>, Region.Op.UNION); <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//第二个</span>
drawScene(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">canvas</span>);</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li></ul>

结果：



先后在(10,10)以及(50,50)为起点，裁剪了两个100*100的矩形，得出的裁剪结果是：

A和B的并集 = A的区域 + B的区域

Op.XOR：

<code class="language-Java hljs mel has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">canvas</span>.clipRect(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">10</span>, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">10</span>, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">110</span>, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">110</span>);        <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//第一个</span>
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">canvas</span>.clipRect(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">50</span>, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">50</span>, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">150</span>, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">150</span>, Region.Op.XOR); <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//第二个</span>
drawScene(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">canvas</span>);</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li></ul>

结果：



先后在(10,10)以及(50,50)为起点，裁剪了两个100*100的矩形，得出的裁剪结果是：

A和B的补集 = A和B的合集 - A和B的交集

Op.REVERSE_DIFFERENCE：

<code class="language-Java hljs mel has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">canvas</span>.clipRect(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">10</span>, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">10</span>, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">110</span>, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">110</span>);        <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//第一个</span>
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">canvas</span>.clipRect(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">50</span>, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">50</span>, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">150</span>, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">150</span>, Region.Op.REVERSE_DIFFERENCE); <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//第二个</span>
drawScene(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">canvas</span>);</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li></ul>

结果：



先后在(10,10)以及(50,50)为起点，裁剪了两个100*100的矩形，得出的裁剪结果是：

B和A的差集 = B - A和B的交集

Op.REPLACE

<code class="language-Java hljs mel has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">canvas</span>.clipRect(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">10</span>, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">10</span>, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">110</span>, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">110</span>);        <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//第一个</span>
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">canvas</span>.clipRect(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">50</span>, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">50</span>, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">150</span>, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">150</span>, Region.Op.REPLACE); <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//第二个</span>
drawScene(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">canvas</span>);</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li></ul>

结果：



先后在(10,10)以及(50,50)为起点，裁剪了两个100*100的矩形，得出的裁剪结果是：

不论A和B的集合状况，B的范围将全部进行显示，如果和A有交集，则将覆盖A的交集范围；

2.Region.Op使用实例：

例子参考自：Android 2D Graphics学习（二）、Canvas篇2、Canvas裁剪和Region、RegionIterator

运行效果图：



关键部分代码 MyView.java：

<code class="language-Java hljs java has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-javadoc" style="color: rgb(136, 0, 0); box-sizing: border-box;">/**
* Created by Jay on 2015/11/10 0010.
*/</span>
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-class" style="box-sizing: border-box;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">class</span> <span class="hljs-title" style="box-sizing: border-box; color: rgb(102, 0, 102);">MyView</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">extends</span> <span class="hljs-title" style="box-sizing: border-box; color: rgb(102, 0, 102);">View</span>{</span>

<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> Bitmap mBitmap = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">null</span>;
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> limitLength = <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>;     <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//</span>
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> width;
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> heigth;
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">static</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">final</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> CLIP_HEIGHT = <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">50</span>;

<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">boolean</span> status = HIDE;<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//显示还是隐藏的状态，最开始为HIDE</span>
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">static</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">final</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">boolean</span> SHOW = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">true</span>;<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//显示图片</span>
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">static</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">final</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">boolean</span> HIDE = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">false</span>;<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//隐藏图片</span>

<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-title" style="box-sizing: border-box;">MyView</span>(Context context) {
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>(context, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">null</span>);
}

<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-title" style="box-sizing: border-box;">MyView</span>(Context context, AttributeSet attrs) {
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">super</span>(context, attrs);
mBitmap = BitmapFactory.decodeResource(getResources(), R.mipmap.img_meizi);
limitLength = width = mBitmap.getWidth();
heigth = mBitmap.getHeight();
}

<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-title" style="box-sizing: border-box;">MyView</span>(Context context, AttributeSet attrs, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> defStyleAttr) {
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">super</span>(context, attrs, defStyleAttr);
}

<span class="hljs-annotation" style="color: rgb(155, 133, 157); box-sizing: border-box;">@Override</span>
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">protected</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">onDraw</span>(Canvas canvas) {
Region region = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> Region();
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> i = <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>;
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">while</span> (i * CLIP_HEIGHT <= heigth) {<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//计算clip的区域</span>
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (i % <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">2</span> == <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>) {
region.union(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> Rect(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>, i * CLIP_HEIGHT, limitLength, (i + <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">1</span>) * CLIP_HEIGHT));
} <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">else</span> {
region.union(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> Rect(width - limitLength, i * CLIP_HEIGHT, width, (i + <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">1</span>)
* CLIP_HEIGHT));
}
i++;
}
canvas.clipRegion(region);
canvas.drawBitmap(mBitmap, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> Paint());
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (status == HIDE) {<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//如果此时是隐藏</span>
limitLength -= <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">10</span>;
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span>(limitLength <= <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>)
status=SHOW;
} <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">else</span> {<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//如果此时是显示</span>
limitLength += <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">5</span>;
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span>(limitLength >= width)
status=HIDE;
}
invalidate();
}
}</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li><li style="box-sizing: border-box; padding: 0px 5px;">26</li><li style="box-sizing: border-box; padding: 0px 5px;">27</li><li style="box-sizing: border-box; padding: 0px 5px;">28</li><li style="box-sizing: border-box; padding: 0px 5px;">29</li><li style="box-sizing: border-box; padding: 0px 5px;">30</li><li style="box-sizing: border-box; padding: 0px 5px;">31</li><li style="box-sizing: border-box; padding: 0px 5px;">32</li><li style="box-sizing: border-box; padding: 0px 5px;">33</li><li style="box-sizing: border-box; padding: 0px 5px;">34</li><li style="box-sizing: border-box; padding: 0px 5px;">35</li><li style="box-sizing: border-box; padding: 0px 5px;">36</li><li style="box-sizing: border-box; padding: 0px 5px;">37</li><li style="box-sizing: border-box; padding: 0px 5px;">38</li><li style="box-sizing: border-box; padding: 0px 5px;">39</li><li style="box-sizing: border-box; padding: 0px 5px;">40</li><li style="box-sizing: border-box; padding: 0px 5px;">41</li><li style="box-sizing: border-box; padding: 0px 5px;">42</li><li style="box-sizing: border-box; padding: 0px 5px;">43</li><li style="box-sizing: border-box; padding: 0px 5px;">44</li><li style="box-sizing: border-box; padding: 0px 5px;">45</li><li style="box-sizing: border-box; padding: 0px 5px;">46</li><li style="box-sizing: border-box; padding: 0px 5px;">47</li><li style="box-sizing: border-box; padding: 0px 5px;">48</li><li style="box-sizing: border-box; padding: 0px 5px;">49</li><li style="box-sizing: border-box; padding: 0px 5px;">50</li><li style="box-sizing: border-box; padding: 0px 5px;">51</li><li style="box-sizing: border-box; padding: 0px 5px;">52</li><li style="box-sizing: border-box; padding: 0px 5px;">53</li><li style="box-sizing: border-box; padding: 0px 5px;">54</li><li style="box-sizing: border-box; padding: 0px 5px;">55</li><li style="box-sizing: border-box; padding: 0px 5px;">56</li><li style="box-sizing: border-box; padding: 0px 5px;">57</li></ul>

实现分析：

初始化的时候获得宽高，然后循环，可以理解把图片分割成一条条的线，循环条件是：i * 每条的高度

不大于高度，然后线又分两种情况，调用的是Region的union，其实就是结合方式为UNINO的剪切方式

而已，最后是对此时图片的是否显示做下判断，隐藏和显示的情况做不同的处理，最后调用invalidate()

重绘！还是蛮简单的，自己理解理解吧~

另外要说一点：Canvas的变换对clipRegion没有作用

3.clipRect方法详解：

clipRect提供了七个重载方法：



参数介绍如下：

rect：Rect对象，用于定义裁剪区的范围，Rect和RectF功能类似，精度和提供的方法不同而已

left：矩形裁剪区的左边位置

top：矩形裁剪区的上边位置

right：矩形裁剪区的右边位置

bottom：矩形裁剪区的下边位置

op：裁剪区域的组合方式

上述四个值可以是浮点型或者整型

使用示例：

<code class="language-Java hljs avrasm has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">        mPaint = new Paint()<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>
mPaint<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.setAntiAlias</span>(true)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>
mPaint<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.setColor</span>(Color<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.BLACK</span>)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>
mPaint<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.setTextSize</span>(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">60</span>)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>

canvas<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.translate</span>(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">300</span>,<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">300</span>)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>
canvas<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.clipRect</span>(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">100</span>, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">100</span>, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">300</span>, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">300</span>)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;                //设置显示范围</span>
canvas<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.drawColor</span>(Color<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.WHITE</span>)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;                      //白色背景</span>
canvas<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.drawText</span>(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"双11，继续吃我的狗粮..."</span>, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">150</span>, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">300</span>, mPaint)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">; //绘制字符串</span></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li></ul>

运行结果：



从上面的例子，不知道你发现了没？

clipRect会受Canvas变换的影响，白色区域是不花的区域，所以clipRect裁剪的是画布，

而我们的绘制是在这个裁剪后的画布上进行的！超过该区域的不显示！

4.clipPath方法详解：

相比起clipRect，clipPath就只有两个重载方法，使用方法非常简单，自己绘制一个Paht然后

传入即可！



使用示例：

这里复用我们以前在ImageView那里写的圆形ImageView的例子~

实现代码：

自定义ImageView：RoundImageView.java

<code class="language-Java hljs java has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-javadoc" style="color: rgb(136, 0, 0); box-sizing: border-box;">/**
* Created by coder-pig on 2015/7/18 0018.
*/</span>
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-class" style="box-sizing: border-box;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">class</span> <span class="hljs-title" style="box-sizing: border-box; color: rgb(102, 0, 102);">RoundImageView</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">extends</span> <span class="hljs-title" style="box-sizing: border-box; color: rgb(102, 0, 102);">ImageView</span> {</span>

<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> Bitmap mBitmap;
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> Rect mRect = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> Rect();
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> PaintFlagsDrawFilter pdf = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> PaintFlagsDrawFilter(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>, Paint.ANTI_ALIAS_FLAG);
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> Paint mPaint = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> Paint();
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> Path mPath=<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> Path();
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-title" style="box-sizing: border-box;">RoundImageView</span>(Context context, AttributeSet attrs) {
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">super</span>(context, attrs);
init();
}

<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//传入一个Bitmap对象</span>
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">setBitmap</span>(Bitmap bitmap) {
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>.mBitmap = bitmap;
}

<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">init</span>() {
mPaint.setStyle(Paint.Style.STROKE);
mPaint.setFlags(Paint.ANTI_ALIAS_FLAG);
mPaint.setAntiAlias(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">true</span>);<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// 抗锯尺</span>
}

<span class="hljs-annotation" style="color: rgb(155, 133, 157); box-sizing: border-box;">@Override</span>
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">protected</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">onDraw</span>(Canvas canvas) {
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">super</span>.onDraw(canvas);
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span>(mBitmap == <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">null</span>)
{
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span>;
}
mRect.set(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>,<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>,getWidth(),getHeight());
canvas.save();
canvas.setDrawFilter(pdf);
mPath.addCircle(getWidth() / <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">2</span>, getWidth() / <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">2</span>, getHeight() / <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">2</span>, Path.Direction.CCW);
canvas.clipPath(mPath, Region.Op.REPLACE);
canvas.drawBitmap(mBitmap, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">null</span>, mRect, mPaint);
canvas.restore();
}
}</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li><li style="box-sizing: border-box; padding: 0px 5px;">26</li><li style="box-sizing: border-box; padding: 0px 5px;">27</li><li style="box-sizing: border-box; padding: 0px 5px;">28</li><li style="box-sizing: border-box; padding: 0px 5px;">29</li><li style="box-sizing: border-box; padding: 0px 5px;">30</li><li style="box-sizing: border-box; padding: 0px 5px;">31</li><li style="box-sizing: border-box; padding: 0px 5px;">32</li><li style="box-sizing: border-box; padding: 0px 5px;">33</li><li style="box-sizing: border-box; padding: 0px 5px;">34</li><li style="box-sizing: border-box; padding: 0px 5px;">35</li><li style="box-sizing: border-box; padding: 0px 5px;">36</li><li style="box-sizing: border-box; padding: 0px 5px;">37</li><li style="box-sizing: border-box; padding: 0px 5px;">38</li><li style="box-sizing: border-box; padding: 0px 5px;">39</li><li style="box-sizing: border-box; padding: 0px 5px;">40</li><li style="box-sizing: border-box; padding: 0px 5px;">41</li><li style="box-sizing: border-box; padding: 0px 5px;">42</li><li style="box-sizing: border-box; padding: 0px 5px;">43</li><li style="box-sizing: border-box; padding: 0px 5px;">44</li><li style="box-sizing: border-box; padding: 0px 5px;">45</li></ul>

布局代码：activity_main.xml:

<code class="language-XML hljs avrasm has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">  <<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">com</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.jay</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.demo</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.imageviewdemo</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.RoundImageView</span>
android:id=<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"@+id/img_round"</span>
android:layout_width=<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"200dp"</span>
android:layout_height=<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"200dp"</span>
android:layout_margin=<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"5px"</span>/></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li></ul>

MainActivity.java:

<code class="language-Java hljs java has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-class" style="box-sizing: border-box;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">class</span> <span class="hljs-title" style="box-sizing: border-box; color: rgb(102, 0, 102);">MainActivity</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">extends</span> <span class="hljs-title" style="box-sizing: border-box; color: rgb(102, 0, 102);">AppCompatActivity</span> {</span>

<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> RoundImageView img_round;

<span class="hljs-annotation" style="color: rgb(155, 133, 157); box-sizing: border-box;">@Override</span>
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">protected</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">onCreate</span>(Bundle savedInstanceState) {
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">super</span>.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
img_round = (RoundImageView) findViewById(R.id.img_round);
Bitmap bitmap = BitmapFactory.decodeResource(getResources(),R.mipmap.meinv);
img_round.setBitmap(bitmap);
}
}</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li></ul>

运行效果图：



另外使用该方法制作的圆角ImageView会有锯齿明显，即使你为Paint，Canvas设置了

抗锯齿也没用~假如你要求高的，可以使用Xfermode-PorterDuff设置图像混排来实现，

基本没锯齿，可见：Android基础入门教程——8.3.6 Paint API之—— Xfermode与PorterDuff详解(三)