OnBackPressed.kt

@SuppressLint("RestrictedApi")
fun onBackPressed() {
    val navController = fragmentManager.findFragmentById(containerId)!!
        .findNavController()

    when {
        navController.backStack.size > 2 ->{
            navController.popBackStack()
        }

        // Fragment back stack is empty so try to go back on the navigation stack
        navigationBackStack.size > 1 -> {
            Log.d(TAG, "logInfo: BNC: backstack size > 1")

            // Remove last item from back stack
            navigationBackStack.removeLast()

            // Update the container with new fragment
            onNavigationItemSelected()
        }
        // If the stack has only one and it's not the navigation home we should
        // ensure that the application always leave from startDestination
        navigationBackStack.last() != appStartDestinationId -> {
            Log.d(TAG, "logInfo: BNC: start != current")
            navigationBackStack.removeLast()
            navigationBackStack.add(0, appStartDestinationId)
            onNavigationItemSelected()
        }
        // Navigation stack is empty, so finish the activity
        else -> {
            Log.d(TAG, "logInfo: BNC: FINISH")
            activity.finish()
        }
    }
}