半透明效果的设置transparent

<resources>
  <style name="Transparent
">
    <item name="android:windowBackground">@color/transparent_background</item>
    <item name="android:windowNoTitle">true</item>
    <item name="android:windowIsTranslucent">true</item>  
    <item name="android:windowAnimationStyle">@+android:style/Animation.Translucent</item>
  </style>
</resources>

　　

<?xml version="1.0" encoding="utf-8"?>
<resources>
  <color name="transparent_background">#50000000</color>
</resources>

　　

<activity android:name=".TransparentActivity" android:theme="@style/Transparent">
</activity>