xml中:
android:background="@android:color/transparent"
半透明:
android:background="#e0000000" />
透明:
android:background="#00000000" />
<?xml version="1.0" encoding="utf-8"?>
<resources>
<color name="transparent_background">#00000000</color>
</resources>
//color.xml的#00000000前两位是透明的效果参数从00--99(透明--不怎么透明),
//后6位是颜色的设置