Brightness regulation - Android Kotlin

///////////////////////////////////////////////////////////////////////////////////////////////////
// In the Activity I have a companion
///////////////////////////////////////////////////////////////////////////////////////////////////
companion object {
    private const val WRITE_SETTINGS_PERMISSION = 100
    private const val MAX_BRIGHTNESS = 255
    private const val MIN_BRIGHTNESS = 20
}

///////////////////////////////////////////////////////////////////////////////////////////////////
// In the onCreate method I have a button that activate permission for brightness
///////////////////////////////////////////////////////////////////////////////////////////////////

// Listener on the onCreate method for a button to grant WRITE_SETTINGS permission
btn_settings_grant_write_permission.setOnClickListener {
    val hasPermissions = hasPermissionsToWriteSettings(this)
    setBrightnessRegulation(hasPermissions)
    if (!hasPermissions) askForPermissionsToWriteSettings(this)
}

// Settings progress bar to change brightness
    skb_settings_brightness.max = MAX_BRIGHTNESS
    skb_settings_brightness.progress = AppPreferences.getInstance(this).brightnessKey
    skb_settings_brightness.setOnSeekBarChangeListener(object : SeekBar.OnSeekBarChangeListener {
        var brightnessProgress = 0

        override fun onProgressChanged(seekBar: SeekBar?, progress: Int, fromUser: Boolean) {
            brightnessProgress = map(progress, 0, MAX_BRIGHTNESS, MIN_BRIGHTNESS, MAX_BRIGHTNESS)
            if (hasPermissionsToWriteSettings(this@SettingsActivity)) {
                Settings.System.putInt(this@SettingsActivity.contentResolver, Settings.System.SCREEN_BRIGHTNESS, brightnessProgress)
                // Do not write this in one-line, won't work
                val lp = this@SettingsActivity.window.attributes
                lp.screenBrightness = brightnessProgress.toFloat() / 255
                this@SettingsActivity.window.attributes = lp
            }
        }

        override fun onStartTrackingTouch(seekBar: SeekBar?) {}

        override fun onStopTrackingTouch(seekBar: SeekBar?) {
            AppPreferences.getInstance(this@SettingsActivity).brightnessKey = brightnessProgress
        }
    })

///////////////////////////////////////////////////////////////////////////////////////////////////
// Helper methods + onRequestPermissionResult
///////////////////////////////////////////////////////////////////////////////////////////////////

// Fun 1, outside (MAYBE HERE YOU CAN FIND THE MISSING LINE)
private fun setBrightnessRegulation(isEnabled: Boolean) {
    if (isEnabled) {
        btn_settings_grant_write_permission.visibility = View.GONE
        skb_settings_brightness.visibility = View.VISIBLE
        Settings.System.putInt(this@SettingsActivity.contentResolver, Settings.System.SCREEN_BRIGHTNESS_MODE, Settings.System.SCREEN_BRIGHTNESS_MODE_MANUAL)
    } else {
        btn_settings_grant_write_permission.visibility = View.VISIBLE
        skb_settings_brightness.visibility = View.GONE
    }
}

// Fun 2, outside
private fun hasPermissionsToWriteSettings(context: Activity): Boolean {
    return if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
        Settings.System.canWrite(context)
    } else {
        ContextCompat.checkSelfPermission(context, Manifest.permission.WRITE_SETTINGS) == PackageManager.PERMISSION_GRANTED
    }
}

// Fun 3, outside
private fun askForPermissionsToWriteSettings(context: Activity) {
    if (!hasPermissionsToWriteSettings(context)) {
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
            val intent = Intent(Settings.ACTION_MANAGE_WRITE_SETTINGS)
            intent.data = Uri.parse("package:" + context.packageName)
            startActivityForResult(intent, WRITE_SETTINGS_PERMISSION)
        } else {
            ActivityCompat.requestPermissions(context, arrayOf(Manifest.permission.WRITE_SETTINGS), WRITE_SETTINGS_PERMISSION)
        }
    }
}

override fun onRequestPermissionsResult(requestCode: Int, permissions: Array<out String>, grantResults: IntArray) {
    when (requestCode) {
        WRITE_SETTINGS_PERMISSION -> {
            if (grantResults.isEmpty() || grantResults[0] != PackageManager.PERMISSION_GRANTED) {
                Toast.makeText(this, R.string.write_settings_permission_denied, Toast.LENGTH_LONG).show()
            } else {
                btn_settings_grant_write_permission.visibility = View.GONE
                skb_settings_brightness.visibility = View.VISIBLE
            }
        }
    }
}

// Map fun
private fun map(currentValue: Int, inputMin: Int, inputMax: Int, outputMin: Int, outputMax: Int): Int {
        return (currentValue - inputMin) * (outputMax - outputMin) / (inputMax - inputMin) + outputMin
    }