dialog_bg_round.xml

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

    <corners android:radius="5dp" />   <!-- 设置圆角弧度 -->
    <solid android:color="#99000000" />   <!-- 设置背景颜色 -->

</shape>