图形—9patch，shape ，selector

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android">
    <!--尺寸-->
    <size android:height="50dp" android:width="100dp"/>

    <!--单色填充-->
    <solid android:color="#f00"/>

    <!--圆角-->
    <corners android:radius="50dp"/>

    <!--边框-->
    <stroke android:color="#0f0" android:width="5dp" android:dashGap="5dp" android:dashWidth="15dp"/>

    <!--渐变色-->
    <gradient android:startColor="#0f0" android:centerColor="#f00" android:endColor="#00f"
        android:angle="45"/>
</shape>

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
    <item android:drawable="@drawable/abc"
      android:state_pressed="true" android:state_checked="true"/><!--按下去的时候--><!--被选中时显示-->
    <item android:drawable="@drawable/bcd"/>

</selector>

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">

    <item android:drawable="@drawable/abc" android:state_pressed="true"/>
    <item android:state_checked="false" android:drawable="@drawable/bcd"/>
</selector>

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">

    <item android:state_pressed="true">
        <shape >
            <solid android:color="#f0f"/>
            <corners android:radius="50dp"/>
        </shape>
    </item>
    <item>
        <shape>
            <solid android:color="#f00"/>
            <corners android:radius="10dp"/>
        </shape>
    </item>
</selector>