<?xml version=“1.0″ encoding=“utf-8″?> 
<style name="translucent">
<item name="android:windowBackground">@color/translucent_background</item>
<item name="android:windowIsTranslucent">true</item>
</style>

<?xml version=“1.0″ encoding=“UTF-8″?> 
<RESOURCES> 
<color name="translucent_background">#60000000</color> 
</RESOURCES> 

　　　Window window=getWindow();
         WindowManager.LayoutParams wl = window.getAttributes();
         wl.flags=WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON;
         wl.alpha=0.6f;    　　這句就是設置窗口里崆件的透明度的．０.０全透明．１.０不透明．
         window.setAttributes(wl);
 

<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> 

public void onCreate(Bundle savedInstanceState) {  
        super.onCreate(savedInstanceState);  
        setTheme(R.style.Transparent);   
        setContentView(R.layout.transparent);  
}