在drawable文件中写

<?xml version="1.0" encoding="utf-8"?>

<shape xmlns:android="http://schemas.android.com/apk/res/android"

android:shape="rectangle" >

<corners android:radius="5dp"/>

<solid android:color="@color/blue"></solid>

<padding

android:top="2dp"

android:bottom="2dp"/>

</shape>