<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android">
         android:shape="rectangle">
         <solid android:color="@color/gray"/>
         <corners
             android:topLeftRadius="8dip"
             android:topRightRadius="8dip"
             android:bottomLeftRadius="8dip"
             android:bottomRightRadius="8dip"/>
</shape>

    <!--shape用于定义形状，有四种形状(矩形rectangle| 椭圆oval | 直线line | 圆形ring)
    //corners用于创建圆角（只用于形状是矩形, solid用于设置填充形状的颜色-->