android 设置系统屏幕亮度_params.screenbrightness 设置无效

说明：

更新后可以立即显示。

关机可保存。

http://daikainan.iteye.com/blog/1455323

/**
	 * 获得当前屏幕亮度的模式    
	 * SCREEN_BRIGHTNESS_MODE_AUTOMATIC=1 为自动调节屏幕亮度
	 * SCREEN_BRIGHTNESS_MODE_MANUAL=0  为手动调节屏幕亮度
	 */
	  private int getScreenMode(){
	    int screenMode=0;
	    try{
	    	screenMode = Settings.System.getInt(getContentResolver(), Settings.System.SCREEN_BRIGHTNESS_MODE);
	    }
	    catch (Exception localException){
	    	
	    }
	    return screenMode;
	  }
	  
	 /**
	 * 获得当前屏幕亮度值  0--255
	 */
	  private int getScreenBrightness(){
	    int screenBrightness=255;
	    try{
	    	screenBrightness = Settings.System.getInt(getContentResolver(), Settings.System.SCREEN_BRIGHTNESS);
	    }
	    catch (Exception localException){
	      
	    }
	    return screenBrightness;
	  }
	/**
	 * 设置当前屏幕亮度的模式    
	 * SCREEN_BRIGHTNESS_MODE_AUTOMATIC=1 为自动调节屏幕亮度
	 * SCREEN_BRIGHTNESS_MODE_MANUAL=0  为手动调节屏幕亮度
	 */
	  private void setScreenMode(int paramInt){
	    try{
	      Settings.System.putInt(getContentResolver(), Settings.System.SCREEN_BRIGHTNESS_MODE, paramInt);
	    }catch (Exception localException){
	      localException.printStackTrace();
	    }
	  }
	  /**
	   * 设置当前屏幕亮度值  0--255
	   */
	  private void saveScreenBrightness(int paramInt){
	    try{
	      Settings.System.putInt(getContentResolver(), Settings.System.SCREEN_BRIGHTNESS, paramInt);
	    }
	    catch (Exception localException){
	      localException.printStackTrace();
	    }
	  }
	  /**
	   * 保存当前的屏幕亮度值，并使之生效
	   */
	  private void setScreenBrightness(int paramInt){
	    Window localWindow = getWindow();
	    WindowManager.LayoutParams localLayoutParams = localWindow.getAttributes();
	    float f = paramInt / 255.0F;
	    localLayoutParams.screenBrightness = f;
	    localWindow.setAttributes(localLayoutParams);
	  }