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androidbrightnessscreen-brightness

How do I detect the screen brightness range on android?

I'm using the following code to set the screen brightness, which works fine on most phones:

    protected fun setBrightness(value: Float) {
        //Set the system brightness using the brightness variable value
        Settings.System.putInt(contentResolver, Settings.System
            .SCREEN_BRIGHTNESS, (value * 255).toInt())
        //Get the current window attributes
        val layoutpars = window.getAttributes()
        //Set the brightness of this window
        layoutpars.screenBrightness = value
        //Apply attribute changes to this window
        window.setAttributes(layoutpars)
    }

When I pass a value of 1, meaning maximum value, this gets converted to 255 which is said to be the greatest value to set the screen brightness. However, on a Xiaomi Mi8 setting the value to 255 won't set the brightness to the full range, as seen in this screenshot:

enter image description here

After printing some debug values and experimenting, it looks like on the Xiaomi Mi8 the maximum brightness value is actually 1024 (or at least, multiplying 1 by that value sets the full brightness bar).

It seems that different android devices might have different brightness scales. Is there some API to get the maximum value in brightness so I don't need to hardcode different constants?

Solution

  • It is specific for some Xiaomi devices. For example Xiaomi Redmi Note 7 has 0-4000 range.

    Official documentation defines SCREEN_BRIGHTNESS range as 0-255. So, I think there are no API to get the maximum value in brightness.

    On some (not all) devices there is a file "/sys/class/leds/lcd-backlight/max_brightness" that can contain max value.