How can I detect the change in brightness on Android and use it simultaneously?

Question

I added SeekBar in Android app. I'm able to change the brightness of the system using SeekBar.

    binding.seekBar.setOnSeekBarChangeListener(object : SeekBar.OnSeekBarChangeListener {
                @RequiresApi(api = Build.VERSION_CODES.M)
                override fun onProgressChanged(p0: SeekBar?, p1: Int, p2: Boolean) {
                    val permission = Settings.System.canWrite(applicationContext)
                    if (permission) {
                        var brightnessValue = p1 * 255 / 100
                        Settings.System.putInt(
                            applicationContext.contentResolver,
                            Settings.System.SCREEN_BRIGHTNESS_MODE,
                            Settings.System.SCREEN_BRIGHTNESS_MODE_AUTOMATIC)
                        Settings.System.putInt(contentResolver, SCREEN_BRIGHTNESS, brightnessValue)
                        binding.seekBar.progress = brightnessValue
    
    
                    } else {
                        val intent = Intent(Settings.ACTION_MANAGE_WRITE_SETTINGS)
                        intent.data = Uri.parse("package:" + applicationContext.packageName)
                        startActivityForResult(intent, 0)
                    }
                }
    
                override fun onStartTrackingTouch(p0: SeekBar?) {
                }
    
                override fun onStopTrackingTouch(p0: SeekBar?) {
    
                }
    
            })

This is how I can see the change in the system on the SeekBar.

    val contentObserver: ContentObserver = object : ContentObserver(Handler()) {
                override fun onChange(selfChange: Boolean) {
                    val a = Settings.System.getInt(contentResolver, SCREEN_BRIGHTNESS, 0)
                    Log.d("MainActivity", "Brightness value: $a")
                    binding.seekBar.progress = a* 255 / 100
                }
            }
            contentResolver.registerContentObserver(
                Settings.System.getUriFor(SCREEN_BRIGHTNESS),
                false, contentObserver
            )   

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.

When I use both together, the code doesn't work. How I can get it to work correctly both when I change it from the system and when I change it on the SeekBar?

Answer 1

I don't know what your actual problem is, but if they work separately but not together, you might have a feedback loop where a seekbar change causes a brightness change which causes a seekbar change which causes a brightness change...

If that's the case, you might want to look at your OnSeekbarChangeListener.onProgressChanged callback - you can't tell from the parameter names you have there, but the last parameter is a boolean that tells you whether the change was caused by a user interaction (i.e. moving the slider) or not (i.e. the value was set programmatically):

public abstract void onProgressChanged (SeekBar seekBar, 
                int progress, 
                boolean fromUser)

So you can check fromUser in onProgressChanged, and only set the system brightness if fromUser is true - otherwise your update is coming from the brightness change itself, and you don't want to set it again.