摘抄自以下博客
shape标签能定义多少种类型的Drawable？
shape 可以定义四种类型的几何图形，由 android:shape 属性指定
line --> 线
rectangle --> 矩形（圆角矩形）
oval --> 椭圆，圆
ring --> 圆环
矩形（边框+填充）
image.png
矩形实线边框内部无填充：rect_solid_border.xml
<?xml version="1.0" encoding="utf-8"?>
<!-- 实线边框 -->
<shape xmlns:android="http://schemas.android.com/apk/res/android"
android:shape="rectangle"
android:useLevel="true">
<stroke
android:width="2dp"
android:color="#ffff0000" />
</shape>
矩形虚线边框内部无填充：rect_dashed_border.xml
<?xml version="1.0" encoding="utf-8"?>
<!-- 虚线边框 -->
<shape xmlns:android="http://schemas.android.com/apk/res/android"
android:shape="rectangle"
android:useLevel="true">
<stroke
android:width="2dp"
android:color="#ffff0000"
android:dashGap="5dp"
android:dashWidth="10dp" />
</shape>
矩形实线边框-内部填充：rect_solid_border_and_fill.xml
<?xml version="1.0" encoding="utf-8"?>
<!-- 实线边框+内部填充 -->
<shape xmlns:android="http://schemas.android.com/apk/res/android"
android:shape="rectangle"
android:useLevel="true">
<stroke
android:width="2dp"
android:color="#ffff0000" />
<solid android:color="#ff00ffff" />
</shape>
矩形虚线边框-内部填充：rect_dashed_border_and_fill.xml
<?xml version="1.0" encoding="utf-8"?>
<!-- 虚线边框+内部填充 -->
<shape xmlns:android="http://schemas.android.com/apk/res/android"
android:shape="rectangle"
android:useLevel="true">
<stroke
android:width="2dp"
android:color="#ffff0000"
android:dashGap="5dp"
android:dashWidth="10dp" />
<solid android:color="#ff00ffff" />
</shape>
圆角矩形
image.png
圆角矩形-只有边框：rect_rounded_border.xml
<?xml version="1.0" encoding="utf-8"?>
<!-- 矩形边框圆角 -->
<shape xmlns:android="http://schemas.android.com/apk/res/android"
android:shape="rectangle"
android:useLevel="true">
<size android:height="100dp"
android:width="100dp"/>
<stroke
android:width="2dp"
android:color="#ffff0000" />
<corners android:bottomLeftRadius="2dp"
android:bottomRightRadius="2dp"
android:topLeftRadius="2dp"
android:topRightRadius="2dp" />
</shape>
圆角矩形-只有内部填充：rect_rounded_fill.xml
<?xml version="1.0" encoding="utf-8"?>
<!-- 圆角矩形 -->
<shape xmlns:android="http://schemas.android.com/apk/res/android"
android:shape="rectangle"
android:useLevel="true">
<size android:height="100dp"
android:width="100dp"/>
<solid android:color="#8000ff00" />
<corners android:bottomLeftRadius="2dp"
android:bottomRightRadius="2dp"
android:topLeftRadius="2dp"
android:topRightRadius="2dp" />
</shape>
圆角矩形-有边框有填充:rect_rounded_border_and_fill.xml
<?xml version="1.0" encoding="utf-8"?>
<!-- 矩形边框+填充 圆角 -->
<shape xmlns:android="http://schemas.android.com/apk/res/android"
android:shape="rectangle"
android:useLevel="true">
<size android:height="100dp"
android:width="100dp"/>
<stroke
android:width="2dp"
android:color="#ffff0000" />
<solid android:color="#8000ff00" />
<corners android:bottomLeftRadius="2dp"
android:bottomRightRadius="2dp"
android:topLeftRadius="2dp"
android:topRightRadius="2dp" />
</shape>
圆角矩形-左边圆角为一个半圆弧：rect_rounded_left_arc.xml
<?xml version="1.0" encoding="utf-8"?>
<!-- 矩形圆角+左右两边为一个圆弧 -->
<shape xmlns:android="http://schemas.android.com/apk/res/android"
android:shape="rectangle"
android:useLevel="true">
<size
android:width="50dp"
android:height="10dp" />
<solid android:color="#8000ff00" />
<!-- 圆角半径是高度的一般就是一个圆弧了 -->
<corners
android:bottomLeftRadius="20dp"
android:topLeftRadius="20dp" />
</shape>
圆角矩形-左右两边都是半圆弧:rect_rounded_left_right_arc.xml
<?xml version="1.0" encoding="utf-8"?>
<!-- 矩形圆角+左右两边为一个圆弧 -->
<shape xmlns:android="http://schemas.android.com/apk/res/android"
android:shape="rectangle"
android:useLevel="true">
<size
android:width="50dp"
android:height="10dp" />
<solid android:color="#8000ff00" />
<!-- 圆角半径是高度的一般就是一个圆弧了 -->
<corners android:radius="20dp" />
</shape>
圆角矩形-左右两边都是半圆弧-带边框：rect_rounded_left_right_arc_border.xml
<?xml version="1.0" encoding="utf-8"?>
<!-- 矩形圆角+左右两边为一个圆弧 -->
<shape xmlns:android="http://schemas.android.com/apk/res/android"
android:shape="rectangle"
android:useLevel="true">
<size
android:width="50dp"
android:height="10dp" />
<stroke android:color="#ffff0000"
android:width="2dp"/>
<solid android:color="#8000ff00" />
<!-- 圆角半径是高度的一般就是一个圆弧了 -->
<corners android:radius="20dp" />
</shape>
圆角矩形-圆：rect_rounded_arc.xml
<?xml version="1.0" encoding="utf-8"?>
<!-- 矩形圆角+圆出一个圆弧 -->
<shape xmlns:android="http://schemas.android.com/apk/res/android"
android:shape="rectangle"
android:useLevel="true">
<size android:height="10dp"
android:width="10dp"/>
<solid android:color="#8000ff00" />
<corners android:radius="20dp" />
</shape>
圆角矩形-上下两边半圆弧:rect_rounded_top_bottom_arc.xml
<?xml version="1.0" encoding="utf-8"?>
<!-- 矩形圆角+左右两边为一个圆弧 -->
<shape xmlns:android="http://schemas.android.com/apk/res/android"
android:shape="rectangle"
android:useLevel="true">
<size
android:width="10dp"
android:height="60dp" />
<solid android:color="#8000ff00" />
<!-- 圆角半径是高度的一般就是一个圆弧了 -->
<corners android:radius="10dp" />
</shape>
渐变效果（以矩形为例）
image.png
垂直线性渐变：rect_gradient_linear_vertical.xml
<?xml version="1.0" encoding="utf-8"?>
<!-- 矩形内部填充-线性垂直渐变 -->
<shape xmlns:android="http://schemas.android.com/apk/res/android"
android:shape="rectangle"
android:useLevel="true">
<size
android:width="@dimen/shape_size"
android:height="@dimen/shape_size" />
<stroke
android:width="1px"
android:color="#ffff00ff" />
<!-- 调整angle实现水平渐变，垂直渐变或者对角渐变 -->
<gradient
android:angle="-45"
android:centerX="0.5"
android:centerY="0.4"
android:centerColor="#8000ff00"
android:endColor="#1000ff00"
android:startColor="#ff00ff00"
android:type="linear" />
</shape>
水平线性渐变:rect_gradient_linear_horizon.xml
<?xml version="1.0" encoding="utf-8"?>
<!-- 矩形内部填充-线性水平渐变 -->
<shape xmlns:android="http://schemas.android.com/apk/res/android"
android:shape="rectangle"
android:useLevel="true">
<size
android:width="@dimen/shape_size"
android:height="@dimen/shape_size" />
<stroke
android:width="1px"
android:color="#ffff00ff" />
<!-- 调整angle实现水平渐变，垂直渐变或者对角渐变 -->
<gradient
android:angle="0"
android:centerX="0.5"
android:centerY="0.5"
android:centerColor="#8000ff00"
android:endColor="#ff00ff00"
android:startColor="#1000ff00"
android:type="linear" />
</shape>
对角线线性渐变：rect_gradient_linear_diagonal.xml
<?xml version="1.0" encoding="utf-8"?>
<!-- 矩形内部填充-线性对角线渐变 -->
<shape xmlns:android="http://schemas.android.com/apk/res/android"
android:shape="rectangle"
android:useLevel="true">
<size
android:width="@dimen/shape_size"
android:height="@dimen/shape_size" />
<stroke
android:width="1px"
android:color="#ffff00ff" />
<!-- 调整angle实现水平渐变，垂直渐变或者对角渐变 -->
<gradient
android:angle="45"
android:centerX="0.5"
android:centerY="0.5"
android:centerColor="#8000ff00"
android:endColor="#1000ff00"
android:startColor="#ff00ff00"
android:type="linear" />
</shape>
径向渐变：rect_gradient_radial.xml
<?xml version="1.0" encoding="utf-8"?>
<!-- 矩形内部填充-径向渐变,一般不用在rect上，用到圆或者椭圆上 -->
<shape xmlns:android="http://schemas.android.com/apk/res/android"
android:shape="rectangle"
android:useLevel="true">
<size
android:width="@dimen/shape_size"
android:height="@dimen/shape_size" />
<stroke
android:width="1px"
android:color="#ffff00ff" />
<!-- 径向渐变angle无效 -->
<gradient
android:angle="0"
android:centerX="0.5"
android:centerY="0.5"
android:startColor="#0000ff00"
android:endColor="#ff00ff00"
android:gradientRadius="40dp"
android:type="radial" />
</shape>
扫描渐变：rect_gradient_sweep.xml
<?xml version="1.0" encoding="utf-8"?>
<!-- 矩形内部填充-扫描渐变 -->
<shape xmlns:android="http://schemas.android.com/apk/res/android"
android:shape="rectangle"
android:useLevel="true">
<!--如果布局中没有设置View的大小，会size设置的大小为默认值-->
<size
android:width="20dp"
android:height="20dp" />
<stroke
android:width="1px"
android:color="#ffff00ff" />
<!--调整angle不能实现角度变化
centerX,centerY是中心点的位置，这里用的是百分比值（0-1）
在rect中gradientRadius无效-->
<gradient
android:angle="0"
android:centerX="0.5"
android:centerY="0.5"
android:startColor="#ff00ff00"
android:gradientRadius="20dp"
android:type="sweep" />
</shape>
