Activity的透明效果

<style name="ActivityTransparentStyle">
<item name="android:windowBackground">@color/alpha</item>
<item name="android:windowNoTitle">true</item>
<item name="android:windowIsTranslucent">true</item>
<item name="android:windowAnimationStyle">@null</item>
</style>

<activity android:name=".Activity" android:theme="@style/ActivityTransparentStyle"/>