FragmentContainerView using findNavController

As per this issue, when using FragmentContainerView, you need to find the NavController using findFragmentById() rather than using findNavController() when in onCreate():

val navHostFragment = supportFragmentManager.findFragmentById(R.id.nav_host_fragment) as NavHostFragmentval navController = navHostFragment.navController

This is because findNavController(R.id.nav_host_fragment) relies on the Fragment's View to already be created which isn't the case when using FragmentContainerView (as it uses a FragmentTransaction under the hood to add the NavHostFragment).

Replace this line:

NavController navController = Navigation.findNavController(this, R.id.nav_host_fragment);

with

NavController navController = getNavController();

Where getNavController() looks like this:

    // workaround for https://issuetracker.google.com/issues/142847973    @NonNull    private NavController getNavController() {        Fragment fragment = getSupportFragmentManager().findFragmentById(R.id.nav_host_fragment);        if (!(fragment instanceof NavHostFragment)) {            throw new IllegalStateException("Activity " + this                    + " does not have a NavHostFragment");        }        return ((NavHostFragment) fragment).getNavController();    }

On top of the accepted answer, a little shortcut what could be used is:

supportFragmentManager.findFragmentById(R.id.navHostMain)?.findNavController()

Regards