调节屏幕亮度

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);

}