透明activity

<style name="Theme.Transparent" parent="@android:style/Theme">  
       <item name="android:windowBackground">@android:color/transparent</item>  
       <item name="android:windowNoTitle">true</item>  
       <item name="android:windowIsFloating">true</item>  
       <item name="android:windowIsTranslucent">true</item>  
       <item name="android:windowContentOverlay">@null</item>  
       <item name="android:backgroundDimEnabled">false</item>  
   </style>

<activity  
            android:name="XXOO"  
            android:theme="@style/Theme.Transparent"  
            android:noHistory="true"  
            android:label="@string/send_activity_name"  
            android:excludeFromRecents="true">   
</activity>