MainActivity.kt

    override fun onConfigurationChanged(newConfig: Configuration) {
        super.onConfigurationChanged(newConfig)
        val isLandscape = newConfig.orientation == Configuration.ORIENTATION_LANDSCAPE
        if (isLandscape) {
            supportActionBar?.hide()
            supportActionBar?.setDisplayShowTitleEnabled(false)
            window.addFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN)
            window.clearFlags(WindowManager.LayoutParams.FLAG_FORCE_NOT_FULLSCREEN)
        } else { // turn OFF full screen
            supportActionBar?.show()
            supportActionBar?.setDisplayShowTitleEnabled(true)
            window.clearFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN)
            window.addFlags(WindowManager.LayoutParams.FLAG_FORCE_NOT_FULLSCREEN)
        }
    }