设置Activity背景圆角

<item name="android:windowBackground">@android:color/transparent</item>

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout    
xmlns:android="http://schemas.android.com/apk/res/android"    
xmlns:tools="http://schemas.android.com/tools"    
android:id="@+id/activity_demo_frame"    
android:layout_width="match_parent"    
android:layout_height="match_parent"    
android:background="@drawable/activity_bg"    
tools:context=".demo.DemoActivity">
</FrameLayout>