自定义控件三部曲之绘图篇(十九)——LinearGradient与闪动文字效果

前言：家和万事兴

相关文章： 
《Android自定义控件三部曲文章索引》：http://blog.csdn.net/harvic880925/article/details/50995268

博主这段时间工作实在是太忙了，全天无尿点……博客一直没更新，实在对不住大家……

这篇就给大家讲setShader的另一个参数，LinearGradient，使用过shape标签的同学，对这个方法估计都不莫生，就是线性渐变。跟PhotoShop中的线性渐变的原理和作用是一样的。这篇文章的最终会实现一个闪动文字效果控件：

一、引言

有关渐变，以前有讲过一篇《详解shape标签》，其中讲述了

<gradient/>

标签的用法：

<code class="language-xml hljs  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-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);">gradient</span>
<span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">android:type</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">["linear"</span> | "<span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">radial</span>" | "<span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">sweep</span>"]    //共有<span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">3</span>中渐变类型，线性渐变（默认）/放射渐变/扫描式渐变
<span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">android:angle</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"integer"</span>     //渐变角度，必须为<span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">45</span>的倍数，<span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">0</span>为从左到右，<span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">90</span>为从上到下
<span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">android:centerX</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"float"</span>     //渐变中心<span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">X</span>的相当位置，范围为<span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">0</span>～<span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">1</span>
<span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">android:centerY</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"float"</span>     //渐变中心<span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">Y</span>的相当位置，范围为<span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">0</span>～<span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">1</span>
<span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">android:startColor</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"color"</span>   //渐变开始点的颜色
<span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">android:centerColor</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"color"</span>  //渐变中间点的颜色，在开始与结束点之间
<span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">android:endColor</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"color"</span>    //渐变结束点的颜色
<span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">android:gradientRadius</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">"float"</span>  //渐变的半径，只有当渐变类型为<span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">radial</span>时才能使用
<span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">android:useLevel</span>=<span class="hljs-value" style="box-sizing: border-box; color: rgb(0, 136, 0);">["true"</span> | "<span class="hljs-attribute" style="box-sizing: border-box; color: rgb(102, 0, 102);">false</span>"] /></span>  //使用LevelListDrawable时就要设置为true。设为false时才有渐变效果    </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><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>

其中的渐变类型有”linear” | “radial” | “sweep”,在代码中对应的类分别是LinearGradient、RaialGradient、SweepGradient；有关

<gradient/>

各个渐变效果的用法，不知道的同学强烈建议你先看看这篇文章。 

这篇我们要讲就是线性渐变的LinearGradient；

二、LinearGradient基本使用

1、构造函数

我们先来看下LinearGradient的构造函数： 
第一个构造函数：

<code class="language-java hljs  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-title" style="box-sizing: border-box;">LinearGradient</span>(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">float</span> x0, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">float</span> y0, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">float</span> x1, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">float</span> y1,<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> color0, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> color1, TileMode tile)</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></ul><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></ul>

用过PhotoShop的线性激变工具的同学，应该都知道，线性渐变其实是在指定的两个点之间填充渐变颜色。 

- 参数中的(x0,y0)就是起始渐变点坐标，参数中(x1,y1)就是结束渐变点坐标； 

- color0就是起始颜色，color1就是终止颜色；颜色值必须使用0xAARRGGBB形式的16进制表示！表示透明度的AA一定不能少。 

- TileMode tile：与BitmapShader一样，用于指定控件区域大于指定的渐变区域时，空白区域的颜色填充方法。

很显然！这个方法，只能指定两种颜色之间的渐变。如果需要多种颜色之间的渐变，就需要使用下面的这个构造函数了。

第二个构造函数：

<code class="language-java hljs  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-title" style="box-sizing: border-box;">LinearGradient</span>(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">float</span> x0, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">float</span> y0, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">float</span> x1, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">float</span> y1,<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> colors[], <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">float</span> positions[], TileMode tile)</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></ul><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></ul>

同样，(x0,y0)就是起始渐变点坐标，参数中(x1,y1)就是结束渐变点坐标 

colors[]用于指定渐变的颜色值数组，同样，颜色值必须使用0xAARRGGBB形式的16进制表示！表示透明度的AA一定不能少。 

positions[]与渐变的颜色相对应，取值是0-1的float类型，表示在每一个颜色在整条渐变线中的百分比位置

2、两色渐变使用示例

我们先来看看两色渐变的构造函数是如何来使用的：

<code class="language-java hljs  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);">LinearGradientView</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> Paint mPaint;
<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;">LinearGradientView</span>(Context context) {
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">super</span>(context);
init();
}

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

<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>(){
setLayerType(LAYER_TYPE_SOFTWARE,<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">null</span>);
mPaint = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> Paint();
}

<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);
mPaint.setShader(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> LinearGradient(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>,getHeight()/<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">2</span>,getWidth(),getHeight()/<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;">0xffff0000</span>,<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0xff00ff00</span>, Shader.TileMode.CLAMP));
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>,getWidth(),getHeight(),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><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></ul><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></ul>

很简单，只需要在绘图的时候构造LinearGradient实例，通过Paint.setShader设置进去即可。 

大家注意一下，我这里设置的渐变范围是从控件的左边中点到右边中点：

<code class="language-java hljs  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.setShader(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> LinearGradient(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>,getHeight()/<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">2</span>,getWidth(),getHeight()/<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;">0xffff0000</span>,<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0xff00ff00</span>, Shader.TileMode.CLAMP));</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></ul><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></ul>

最后通过canvas.drawRect把整个控件区域画出来：

<code class="language-java hljs  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;">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>,getWidth(),getHeight(),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></ul><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></ul>

这里大家注意一下，上面我们也已经提到了，颜色值必须使用0xAARRGGBB的完整16进制的颜色样式表示，我们这里的颜色值就是0xffff0000和0xff00ff00；大家自己可以进行尝试，如果把红色的透明度值去掉，改写成0xff00000，是不会有任何显示的。 

效果图如下： 

3、多色渐变使用示例

下面我们来看第二个构造函数，多色渐变的使用方法：

<code class="language-java hljs  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;">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;">int</span>[] colors = {<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0xffff0000</span>,<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0xff00ff00</span>,<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0xff0000ff</span>,<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0xffffff00</span>,<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0xff00ffff</span>};
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">float</span>[]  pos = {<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>f,<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0.2</span>f,<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0.4</span>f,<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0.6</span>f,<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">1.0</span>f};
LinearGradient multiGradient = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> LinearGradient(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>,getHeight()/<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">2</span>,getWidth(),getHeight()/<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">2</span>,colors,pos, Shader.TileMode.CLAMP);
mPaint.setShader(multiGradient);
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>,getWidth(),getHeight(),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></ul><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></ul>

从这里可以看出，渐变的开始点同样是控件左边中点，渐变的结束点也同样是控件右边中点；这里我们指定了五种渐变颜色，而且指定了每个颜色的位置，前四种颜色是按20%均匀分布的，最后两种颜色相距40%；最后通过canvas.drawRect把整个控件区域画出来

效果图如下： 



注意： 

colors和pos的个数一定要相等，也就是说必须指定每一个颜色值的位置！如果多或少都会直接报错：（Signal 11是SO内部错误） 

2、渐变起始坐标与填充的关系——矩形填充

我们上面的示例中都是从控件左边中间到控件右边中点；如果我们改成从左上角到右上角的填充方式，结果会怎样呢？

<code class="language-java hljs  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;">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;">int</span>[] colors = {<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0xffff0000</span>,<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0xff00ff00</span>,<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0xff0000ff</span>,<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0xffffff00</span>,<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0xff00ffff</span>};
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">float</span>[]  pos = {<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>f,<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0.2</span>f,<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0.4</span>f,<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0.6</span>f,<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">1.0</span>f};
LinearGradient multiGradient = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> LinearGradient(<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(),colors,pos, Shader.TileMode.CLAMP);
mPaint.setShader(multiGradient);
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>,getWidth(),getHeight(),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></ul><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></ul>

渐变线是从控件的左上角到控件的右下角位置：

<code class="language-java hljs  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;">LinearGradient multiGradient = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> LinearGradient(<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(),colors,pos, Shader.TileMode.CLAMP);</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></ul><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></ul>

效果图如下： 


 

形成原理如下： 


 

就是说，首先是两个渐变点之间连线，然后以连线为对角线形成一个矩形，各种颜色都是以这条对角线为矩形的填充的。

3、TileMode重复方式

在讲到BitmapShader的时候，我们已经详细讲过TileMode的意义：当控件区域大小渐变区域时，用于填充空白位置的。 

下面我们就逐个看一下TileMode不同时，对于线性渐变的有什么作用。 
（1）、X、Y轴共用填充参数 

首先，我们再回来看一下LinearGradient的构造函数：

<code class="language-java hljs  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-title" style="box-sizing: border-box;">LinearGradient</span>(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">float</span> x0, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">float</span> y0, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">float</span> x1, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">float</span> y1,<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> colors[], <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">float</span> positions[], TileMode tile)
<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;">LinearGradient</span>(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">float</span> x0, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">float</span> y0, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">float</span> x1, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">float</span> y1,<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> color0, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> color1, TileMode tile)</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></ul><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></ul>

从构造函数中可以看出，LiearGradient只有一个TileMode参数，这说明X轴与Y轴共用这一个TileMode填充参数，而不能像BitmapShader那样分别指定X轴与Y轴的填充参数。 
（2）、TileMode.CLAMP

<code class="language-java hljs  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;">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-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">////        多色渐变</span>
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span>[] colors = {<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0xffff0000</span>,<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0xff00ff00</span>,<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0xff0000ff</span>,<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0xffffff00</span>,<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0xff00ffff</span>};
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">float</span>[]  pos = {<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>f,<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0.2</span>f,<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0.4</span>f,<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0.6</span>f,<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">1.0</span>f};
LinearGradient multiGradient = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> LinearGradient(<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()/<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>,colors,pos, Shader.TileMode.CLAMP);
mPaint.setShader(multiGradient);
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>,getWidth(),getHeight(),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></ul><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>

这里做了一个多色渐变，渐变点是从(0,0)到屏幕的中间点(width/2,height.2)； 

效果图如下： 


 

从效果图中可以看到，效果很好理解，就是以(0,0)到(width/2,height.2)为矩形对角线，来填充各种颜色渐变，对于之外的区域，用边缘色彩来填充。 
（3）、TileMode.REPEAT 

同样是上面的代码，渐变点是从(0,0)到屏幕的中间点(width/2,height.2)，当空白区域填充模式改为TileMode.REPEAT时，效果图如下： 


 

大家初次看到这个效果，可能一脸懵逼 —_—!!!, 其实也不难理解，我们需要先找到哪块是我们的渐变，哪块是空白像素的填充： 



在这个图中，蓝色块是我们原始的渐变图形，从从(0,0)到屏幕的中间点(width/2,height.2)，另外的没有遮起来的部分是空白位置填充的。 

在填充时，结束点做为填充点的起点，即填充的线性渐变的位置为从(width/2,height/2)到(width,height)，即从中间点到右下角点位置的填充。 
（4）、TileMode.MIRROR 

同样，如果我们把填充模式改为镜像模式，效果图如下： 


 

很容易理解，就不再讲了。

4、填充方式：从控件左上角开始填充

与BitmapShader一样，同样是从控件左上角开始填充整个控件，利用canvas.drawXXX系列函数只是用来指定显示哪一块 

比如：

<code class="language-java hljs  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;">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-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//多色渐变</span>
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span>[] colors = {<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0xffff0000</span>,<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0xff00ff00</span>,<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0xff0000ff</span>,<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0xffffff00</span>,<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0xff00ffff</span>};
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">float</span>[]  pos = {<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>f,<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0.2</span>f,<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0.4</span>f,<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0.6</span>f,<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">1.0</span>f};
LinearGradient multiGradient = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> LinearGradient(<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()/<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>,colors,pos, Shader.TileMode.MIRROR);
mPaint.setShader(multiGradient);
canvas.drawRect(<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;">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></ul><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>

同样是使用镜像模式，但我们不再全屏绘制，而只是绘出其中一小部分： 


 

我们再来看看全屏绘制的镜像模式的效果图： 


 

很明显，这里所绘制的一小块，跟从全屏绘制的效果图上摘下来的一块一样。

这就说明了： 

无论哪种Shader，都是从控件的左上角开始填充的，利用canvas.drawXXX系列函数只是用来指定显示哪一块

我们说了如果利用drawXXX系列函数只是用来指定显示哪一块，那如果我们利用DrawText来显示，那是不是就会显示出彩色文字了？

<code class="language-java hljs  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;">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-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//多色渐变</span>
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span>[] colors = {<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0xffff0000</span>,<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0xff00ff00</span>,<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0xff0000ff</span>,<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0xffffff00</span>,<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0xff00ffff</span>};
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">float</span>[]  pos = {<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>f,<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0.2</span>f,<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0.4</span>f,<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0.6</span>f,<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">1.0</span>f};
LinearGradient multiGradient = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> LinearGradient(<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()/<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>,colors,pos, Shader.TileMode.MIRROR);
mPaint.setShader(multiGradient);
mPaint.setTextSize(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">50</span>);
canvas.drawText(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"欢迎关注启舰的blog"</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>,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><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>

效果图如下： 


 

有没有感觉很酷炫……看似牛逼的效果其实就是这么简单…… 

如果我们把渐变效果移动起来，就直接实现了我们开篇时说的文字渐变的动画效果了。 

下面我们加入动画，让颜色动起来吧

三、闪光字符串实现

这部分我们要实现的效果图如下： 


 

闪光效果有木有……看起来很碉堡吧，我们就来具体看下原理吧，这个控件只给大家讲基本原理，就不再封装成控件了，博主近期太忙了，大家自己封装下吧…… 

我们先来看下原理图：

1、原理

（1）、初始状态

首先，我们要有一个渐变的LinearGradient,颜色是从文字颜色的黑色到中间的绿色，然后再到黑色，填充模式为 Shader.TileMode.CLAMP，初始的位置在文字的左侧； 

对应图像为： 


 

我这里为了表述文字效果，特地做了几个处理； 

1.首先我把渐变图像用红边框了起来。由于填充模式是Shader.TileMode.CLAMP，所以右侧文字的位置会被填充为边缘颜色黑色 

2.为了表述当前文字的位置，我特地把文字写成了红色。而文字真正的颜色应该是其底部LinearGradient的填充色才对的，大家这点注意。 

对应代码为：

<code class="language-java hljs  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;">mLinearGradient = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> LinearGradient(- getMeasuredWidth(),<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;">0</span>,<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span>[]{
getCurrentTextColor(),<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0xff00ff00</span>,getCurrentTextColor()},
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">float</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;">0.5</span>f,
<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">1</span>
},
Shader.TileMode.CLAMP
);
}</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><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>

（2）、运动中

下图显示的是当渐变的LinearGradient移动到文字部分的时的状态 


 

由于使用的是Shader.TileMode.CLAMP填充模式，所以两次空白区域都会被填充为LinearGradient的边缘颜色，即文字的黑色。 

上面我们讲了，文字会显示其下方LinearGradient的填充颜色，所以现在文字的文字就会有一部分变绿了。

（3）、终止状态

在终止状态时，LinearGradient移动到文字的右侧 


 

同样是由于Shader.TileMode.CLAMP填充模式，文字会被填充为文字原本的颜色。

从上面的原理中，我们需要理出来几个点： 

第一：创建的LinearGradient渐变的构造方法，前面已经列出来代码了，初始位置是在文字左侧的，而且大小与文字所占位置相同，填充模式使用边缘填充 

第二：从起始位置和终止位置可以看出，LinearGradient渐变的运动长度是两个文字的长度。

二、代码实现

其实看了原理之后，实现起来就没有什么难度了，我们还是列出完整代码，然后针对性的讲一点就可以了，如果大家还没看懂，可以把示例源码下下来，自己再研究研究

<code class="language-java hljs  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);">ShimmerTextView</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);">TextView</span> {</span>
<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;">private</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> mDx;
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> LinearGradient mLinearGradient;
<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;">ShimmerTextView</span>(Context context) {
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">super</span>(context);
init();
}

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

<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 =getPaint();
}

<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;">onLayout</span>(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">boolean</span> changed, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> left, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> top, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> right, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> bottom) {
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">super</span>.onLayout(changed, left, top, right, bottom);

ValueAnimator animator = ValueAnimator.ofInt(<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;">2</span>*getMeasuredWidth());
animator.addUpdateListener(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> ValueAnimator.AnimatorUpdateListener() {
<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;">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;">onAnimationUpdate</span>(ValueAnimator animation) {
mDx = (Integer) animation.getAnimatedValue();
postInvalidate();
}
});
animator.setRepeatMode(ValueAnimator.RESTART);
animator.setRepeatCount(ValueAnimator.INFINITE);
animator.setDuration(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">2000</span>);
animator.start();

mLinearGradient = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> LinearGradient(- getMeasuredWidth(),<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;">0</span>,<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span>[]{
getCurrentTextColor(),<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0xff00ff00</span>,getCurrentTextColor()
},
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">float</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;">0.5</span>f,
<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">1</span>
},
Shader.TileMode.CLAMP
);
}

<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) {

Matrix matrix = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> Matrix();
matrix.setTranslate(mDx,<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>);
mLinearGradient.setLocalMatrix(matrix);
mPaint.setShader(mLinearGradient);

<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">super</span>.onDraw(canvas);
}
}</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><li style="box-sizing: border-box; padding: 0px 5px;">58</li><li style="box-sizing: border-box; padding: 0px 5px;">59</li><li style="box-sizing: border-box; padding: 0px 5px;">60</li><li style="box-sizing: border-box; padding: 0px 5px;">61</li><li style="box-sizing: border-box; padding: 0px 5px;">62</li><li style="box-sizing: border-box; padding: 0px 5px;">63</li></ul><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><li style="box-sizing: border-box; padding: 0px 5px;">58</li><li style="box-sizing: border-box; padding: 0px 5px;">59</li><li style="box-sizing: border-box; padding: 0px 5px;">60</li><li style="box-sizing: border-box; padding: 0px 5px;">61</li><li style="box-sizing: border-box; padding: 0px 5px;">62</li><li style="box-sizing: border-box; padding: 0px 5px;">63</li></ul>

1、派生自TextView 

首先需要注意的是，控件派生自TextView，所以可以使用TextView的自带方法getCurrentTextColor()来获取文字颜色。 
2、如何移动LinearGradient 

然后，上面我们讲了如何给文字加上渐变效果，其实让它动起来办法很简单，还记得我们说过Shader有一个setLocalMatrix(Matrix localM) 方法可以设置位置矩阵么，我们只需要给LinearGradient设置上逐渐平移的矩阵就可以了。 

比如：

<code class="language-java hljs  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-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) {

Matrix matrix = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> Matrix();
matrix.setTranslate(mDx,<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>);
mLinearGradient.setLocalMatrix(matrix);
mPaint.setShader(mLinearGradient);

<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">super</span>.onDraw(canvas);
}</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><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>

其中向右偏移的距离mDx，是由ValueAnimator生成的； 
3、ValueAnimator的创建 

前面我们讲了LinearGradient移动距离是从0到两倍的text距离，我们通过getMeasuredWidth()可以得到TextView的宽度，乘以2就可以了，创建代码如下：

<code class="language-java hljs  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;">ValueAnimator animator = ValueAnimator.ofInt(<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;">2</span>*getMeasuredWidth());
animator.addUpdateListener(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> ValueAnimator.AnimatorUpdateListener() {
<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;">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;">onAnimationUpdate</span>(ValueAnimator animation) {
mDx = (Integer) animation.getAnimatedValue();
postInvalidate();
}
});
animator.setRepeatMode(ValueAnimator.RESTART);
animator.setRepeatCount(ValueAnimator.INFINITE);
animator.setDuration(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">2000</span>);
animator.start();</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></ul><div class="save_code tracking-ad" data-mod="popu_249" style="box-sizing: border-box; position: absolute; height: 60px; right: 30px; top: 5px; color: rgb(255, 255, 255); cursor: pointer; z-index: 2;"><a target=_blank target="_blank" style="color: rgb(51, 102, 153); box-sizing: border-box;"><img src="http://static.blog.csdn.net/images/save_snippets.png" style="border: none; box-sizing: border-box; max-width: 100%;" alt="" /></a></div><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></ul>

有关ValueAnimator的使用方法，如果有不理解的同学，请先去看《Android自定义三部曲之动画篇》；

好了，本篇到这里就结束了，下篇我们再来看最后一个渐变RadialGradient的使用方法与效果吧。

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源码下载地址：http://download.csdn.net/detail/harvic880925/9615494 

转载请标明出处，http://blog.csdn.net/harvic880925/article/details/52350154谢谢