android 如何构建背景渐变的页面

shape.xml:

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="https://schemas.android.com/apk/res/android"
	android:shape="rectangle">
	<gradient android:startColor="#FF123456" android:endColor="#FF654321"
		android:angle="270" />
</shape>
<?xml version="1.0" encoding="utf-