SVG & VectorDrawable

VectorDrawable

Android L开始提供了新的API VectorDrawable 可以使用SVG类型的资源，也就是矢量图。在xml文件中的标签是<vector>，下面是一个例子

<code class="language-xml hljs  has-numbering" style="display: block; padding: 0px; background-color: transparent; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-top-left-radius: 0px; border-top-right-radius: 0px; border-bottom-right-radius: 0px; border-bottom-left-radius: 0px; word-wrap: normal; background-position: initial initial; background-repeat: initial initial;"><span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;"><!-- res/drawable/heart.xml --></span>
<span class="hljs-tag" style="color: rgb(0, 102, 102); box-sizing: border-box;"><<span class="hljs-title" style="box-sizing: border-box; color: rgb(0, 0, 136);">vector</span> <span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">xmlns:android</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"http://schemas.android.com/apk/res/android"</span>
    <!<span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">--</span> <span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">intrinsic</span> <span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">size</span> <span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">of</span> <span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">the</span> <span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">drawable</span> <span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">--</span>></span>
    android:height="256dp"
    android:width="256dp"
    <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;"><!-- size of the virtual canvas --></span>
    android:viewportWidth="32"
    android:viewportHeight="32">

  <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;"><!-- draw a path --></span>
  <span class="hljs-tag" style="color: rgb(0, 102, 102); box-sizing: border-box;"><<span class="hljs-title" style="box-sizing: border-box; color: rgb(0, 0, 136);">path</span> <span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">android:fillColor</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"#8fff"</span>
      <span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">android:pathData</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"M20.5,9.5
                        c-1.955,0,-3.83,1.268,-4.5,3
                        c-0.67,-1.732,-2.547,-3,-4.5,-3
                        C8.957,9.5,7,11.432,7,14
                        c0,3.53,3.793,6.257,9,11.5
                        c5.207,-5.242,9,-7.97,9,-11.5
                        C25,11.432,23.043,9.5,20.5,9.5z"</span> /></span>
<span class="hljs-tag" style="color: rgb(0, 102, 102); box-sizing: border-box;"></<span class="hljs-title" style="box-sizing: border-box; color: rgb(0, 0, 136);">vector</span>></span></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; background-color: rgb(238, 238, 238); 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;"><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></ul>

这样就定义好了一个静态的矢量图，可以像一般的图片资源使用，设置到imageView中会显示出一个心形。控制显示心形的就是上面path这个标签，一个path代表一个元素，绘制的内容是pathData下的一长串字符，里面是SVG绘制的一系列命令，提供moveTo、lineTo、close等操作，可以和Graphics 中的Path操作对应起来，具体可以查看SVG path Ref，后面会简要说明一下。 
VectorDrawable定义的是一张静态图，还有一个类AnimatedVectorDrawable，可以让矢量图有动画效果。一般需要三个步骤：

• 定义VectorDrawable

<code class="language-xml hljs  has-numbering" style="display: block; padding: 0px; background-color: transparent; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-top-left-radius: 0px; border-top-right-radius: 0px; border-bottom-right-radius: 0px; border-bottom-left-radius: 0px; word-wrap: normal; background-position: initial initial; background-repeat: initial initial;"><span class="hljs-tag" style="color: rgb(0, 102, 102); box-sizing: border-box;"><<span class="hljs-title" style="box-sizing: border-box; color: rgb(0, 0, 136);">vector</span> <span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">xmlns:android</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"http://schemas.android.com/apk/res/android"</span>
     <span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">android:height</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"64dp"</span>
     <span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">android:width</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"64dp"</span>
     <span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">android:viewportHeight</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"600"</span>
     <span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">android:viewportWidth</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"600"</span> ></span>
     <span class="hljs-tag" style="color: rgb(0, 102, 102); box-sizing: border-box;"><<span class="hljs-title" style="box-sizing: border-box; color: rgb(0, 0, 136);">group
</span>         <span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">android:name</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"rotationGroup"</span>
         <span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">android:pivotX</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"300.0"</span>
         <span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">android:pivotY</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"300.0"</span>
         <span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">android:rotation</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"45.0"</span> ></span>
         <span class="hljs-tag" style="color: rgb(0, 102, 102); box-sizing: border-box;"><<span class="hljs-title" style="box-sizing: border-box; color: rgb(0, 0, 136);">path
</span>             <span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">android:name</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"v"</span>
             <span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">android:fillColor</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"#000000"</span>
             <span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">android:pathData</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"M300,70 l 0,-70 70,70 0,0 -70,70z"</span> /></span>
     <span class="hljs-tag" style="color: rgb(0, 102, 102); box-sizing: border-box;"></<span class="hljs-title" style="box-sizing: border-box; color: rgb(0, 0, 136);">group</span>></span>
 <span class="hljs-tag" style="color: rgb(0, 102, 102); box-sizing: border-box;"></<span class="hljs-title" style="box-sizing: border-box; color: rgb(0, 0, 136);">vector</span>></span></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; background-color: rgb(238, 238, 238); 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;"><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></ul>

• 定义AnimatedVectorDrawable，给上面矢量图的元素添加动画

<code class="language-xml hljs  has-numbering" style="display: block; padding: 0px; background-color: transparent; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-top-left-radius: 0px; border-top-right-radius: 0px; border-bottom-right-radius: 0px; border-bottom-left-radius: 0px; word-wrap: normal; background-position: initial initial; background-repeat: initial initial;"><span class="hljs-tag" style="color: rgb(0, 102, 102); box-sizing: border-box;"><<span class="hljs-title" style="box-sizing: border-box; color: rgb(0, 0, 136);">animated-vector</span> <span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">xmlns:android</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"http://schemas.android.com/apk/res/android"</span>
   <span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">android:drawable</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"@drawable/vectordrawable"</span> ></span>
     <span class="hljs-tag" style="color: rgb(0, 102, 102); box-sizing: border-box;"><<span class="hljs-title" style="box-sizing: border-box; color: rgb(0, 0, 136);">target
</span>         <span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">android:name</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"rotationGroup"</span>
         <span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">android:animation</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"@anim/rotation"</span> /></span>
     <span class="hljs-tag" style="color: rgb(0, 102, 102); box-sizing: border-box;"><<span class="hljs-title" style="box-sizing: border-box; color: rgb(0, 0, 136);">target
</span>         <span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">android:name</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"v"</span>
         <span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">android:animation</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"@anim/path_morph"</span> /></span>
 <span class="hljs-tag" style="color: rgb(0, 102, 102); box-sizing: border-box;"></<span class="hljs-title" style="box-sizing: border-box; color: rgb(0, 0, 136);">animated-vector</span>></span></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; background-color: rgb(238, 238, 238); 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;"><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>

• 定义动画文件

<code class="language-xml hljs  has-numbering" style="display: block; padding: 0px; background-color: transparent; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-top-left-radius: 0px; border-top-right-radius: 0px; border-bottom-right-radius: 0px; border-bottom-left-radius: 0px; word-wrap: normal; background-position: initial initial; background-repeat: initial initial;"><span class="hljs-tag" style="color: rgb(0, 102, 102); box-sizing: border-box;"><<span class="hljs-title" style="box-sizing: border-box; color: rgb(0, 0, 136);">objectAnimator
</span>     <span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">android:duration</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"6000"</span>
     <span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">android:propertyName</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"rotation"</span>
     <span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">android:valueFrom</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"0"</span>
     <span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">android:valueTo</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"360"</span> /></span></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; background-color: rgb(238, 238, 238); 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;"><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>

<code class="language-xml hljs  has-numbering" style="display: block; padding: 0px; background-color: transparent; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-top-left-radius: 0px; border-top-right-radius: 0px; border-bottom-right-radius: 0px; border-bottom-left-radius: 0px; word-wrap: normal; background-position: initial initial; background-repeat: initial initial;"><span class="hljs-tag" style="color: rgb(0, 102, 102); box-sizing: border-box;"><<span class="hljs-title" style="box-sizing: border-box; color: rgb(0, 0, 136);">set</span> <span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">xmlns:android</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"http://schemas.android.com/apk/res/android"</span>></span>
     <span class="hljs-tag" style="color: rgb(0, 102, 102); box-sizing: border-box;"><<span class="hljs-title" style="box-sizing: border-box; color: rgb(0, 0, 136);">objectAnimator
</span>         <span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">android:duration</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"3000"</span>
         <span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">android:propertyName</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"pathData"</span>
         <span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">android:valueFrom</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"M300,70 l 0,-70 70,70 0,0   -70,70z"</span>
         <span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">android:valueTo</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"M300,70 l 0,-70 70,0  0,140 -70,0 z"</span>
         <span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">android:valueType</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"pathType"</span>/></span>
 <span class="hljs-tag" style="color: rgb(0, 102, 102); box-sizing: border-box;"></<span class="hljs-title" style="box-sizing: border-box; color: rgb(0, 0, 136);">set</span>></span></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; background-color: rgb(238, 238, 238); 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;"><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></ul>

由于矢量图的特点，AnimatedVectorDawable可以实现一些很特别的效果，对VectorDrawable里的pathData做动画，可以从一个图形渐变到另一个图形，比如Material Design里的toolbar icon；对trimPathStart、trimPathEnd做动画，可以得到图形的绘制轨迹。

SVG Path Data

主要有以下一些命令

• M： move to 移动绘制点
• L：line to 直线
• Z：close 闭合
• C：cubic bezier 三次贝塞尔曲线
• Q：quatratic bezier 二次贝塞尔曲线
• A：ellipse 圆弧

每个命令都有大小写形式，大写代表后面的参数是绝对坐标，小写表示相对坐标。参数之间用空格或逗号隔开

命令详解：

• M (x y) 移动到x,y
• L (x y) 直线连到x,y，还有简化命令H(x) 水平连接、V(y)垂直连接
• Z，没有参数，连接起点和终点
• C(x1 y1 x2 y2 x y)，控制点x1,y1 x2,y2，终点x,y
• Q(x1 y1 x y)，控制点x1,y1，终点x,y
• A(rx ry x-axis-rotation large-arc-flag sweep-flag x y) 
  rx ry 椭圆半径 
  x-axis-rotation x轴旋转角度 
  large-arc-flag 为0时表示取小弧度，1时取大弧度 
  sweep-flag 0取逆时针方向，1取顺时针方向 
  有个图解： 
  

应用

在github上看到一个VectorDrawable应用的例子，实现了一个动态效果的searchbar，原理就是对VectorDrawable trimPathStart这个属性做动画。最初的设计在这里，照着实现一下：

Reference

• https://developer.android.com/training/material/drawables.html
• https://developer.android.com/reference/android/graphics/drawable/VectorDrawable.html
• https://developer.android.com/reference/android/graphics/drawable/AnimatedVectorDrawable.html
• http://www.w3.org/TR/SVG11/paths.html#PathData

转子  http://blog.csdn.net/xu_fu/article/details/44004841