调节屏幕亮度

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