android 調節屏幕亮度

public void setBrightness(int level) { 
 ContentResolver cr = getContentResolver(); 
 Settings.System.putInt(cr, "screen_brightness", level); 
 Window window = getWindow(); 
 LayoutParams attributes = window.getAttributes(); 
 float flevel = level; 
 attributes.screenBrightness = flevel / 255; 
 getWindow().setAttributes(attributes); 
}