How to dim screen to zero without conflicting with FLAG_KEEP_SCREEN_ON

Question

I found several methods to dim the screen but I am unsure how they work in concert with FLAG_KEEP_SCREEN_ON:

• Settings.System.SCREEN_BRIGHTNESS
• IHardwareService.setScreenBacklight()
• WindowManager.LayoutParams.screenBrightness

Which of the above methods will keep the screen on, even if I set brightness to 0.0?

Answer 1

Nothing will work reliably. If you set the brightness to 0 on some devices it will turn off the screen (but the device will be in a funny state for about 5 seconds or so before really realizing it's off and acting as such). Some devices it will be on but black.

IIRC LayoutParams.screenBrightness with a value less than 30 is unreliable in that it might turn off the display.

On an AMOLED device a full screen that's all black will not have backlight. But SLCD definitely will. Also on Android 3.0 you can't have a full screen as the system bar is always visible.