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Seems like using the FragmentContainerView doesn't work right out of the box?

<androidx.fragment.app.FragmentContainerView
        class="androidx.navigation.fragment.NavHostFragment"
        android:id="@+id/fragment_nav_host"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        app:defaultNavHost="true"
        app:navGraph="@navigation/nav_app" />
Here's my code using fragment-ktx:1.2.0-rc01 and I'm just always getting this error:
Caused by: java.lang.IllegalStateException: Activity ...MainActivity@797467d does not have a NavController set on 2131296504
Just using <fragment> works and AFAIK, it's just supposed to be replaced by FragmentContainerView.
Am I missing something or was anyone able to use FragmentContainerView as a NavHostFragment?
Many thanks!
Due to this bug-report:
https://issuetracker.google.com/issues/142847973
This is the only way (currently):
val navHostFragment = supportFragmentManager
    .findFragmentById(R.id.my_nav_host_fragment) as NavHostFragment
val navController = navHostFragment.navController
(Java):
NavHostFragment navHostFragment =
    (NavHostFragment) getSupportFragmentManager()
        .findFragmentById(R.id.my_nav_host_fragment);
NavController navController = navHostFragment.getNavController();
                surely better just to use fragmentrather than worrying about having to remember to use this workaround? We were seeing crashes but only for some users, weird...
– hmac
                Mar 19, 2020 at 9:40
                @hmac In the issue linked they discuss why you shouldn't use fragment: issuetracker.google.com/issues/142847973#comment15: The Lint check is there exactly because you absolutely should switch over to FragmentContainerView in all cases.
– Banana
                Aug 10, 2020 at 14:18
August 2020 update
Here is the solution recommended by the official Android documentation.
Kotlin version:
val navHostFragment = supportFragmentManager.findFragmentById(R.id.nav_host_fragment) as NavHostFragment
val navController = navHostFragment.navController
Java version:
NavHostFragment navHostFragment = supportFragmentManager.findFragmentById(R.id.nav_host_fragment);
NavController navController = navHostFragment.getNavController();
I quote the doc:
When creating the NavHostFragment using FragmentContainerView or if
manually adding the NavHostFragment to your activity via a
FragmentTransaction, attempting to retrieve the NavController in
onCreate() of an Activity via Navigation.findNavController(Activity,
@IdRes int) will fail. You should retrieve the NavController directly
from the NavHostFragment instead.
The bug-report reported by Ove Stoerholt will not be fixed. You can see here the "Won't Fix (Infeasible)" status.
                While the original task was tagged as "Won't Fix (Infeasible)", they did link to another task so they might plan to fix the issue after all: issuetracker.google.com/issues/143145612
– Sharp
                Oct 25, 2020 at 10:04
// Set up navigation - action bar and sidebar.
/// Let the navigation view check/uncheck the menu items.
nav_view.post { // wait for NavHostFragment to inflate
    val navController = findNavController()
    nav_view.setupWithNavController(navController)
    nav_view.setNavigationItemSelectedListener(this)
Java8 (with lambda):
navigationView.post(() -> { // wait for NavHostFragment to inflate
    navController = Navigation.findNavController(activity, R.id.nav_host_fragment);
    NavigationUI.setupWithNavController(navView, navController);
    navView.setNavigationItemSelectedListener(navItemSelectedListener);
                I had used <fragment> to avoid the bug. But I was troubled another unknown error. So I found this @Pnemonic's late answer and tried it in order to use <FragmentContainerView>. The problem has been cleared, thank you!
– hata
                May 25, 2020 at 6:36
I have the same problem when using kotlin:
val navHostFragment = supportFragmentManager.findFragmentById(R.id.nav_host_fragment) as NavHostFragment
val navController = navHostFragment.navController
Just add it to
setupActionBarWithNavController(navController)
<androidx.fragment.app.FragmentContainerView
    android:name="androidx.navigation.fragment.NavHostFragment"
        
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