FragmentContainerView as NavHostFragment

Question

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!

Answer 1

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(); 

Answer 2

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.

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The bug-report reported by Ove Stoerholt will not be fixed. You can see here the "Won't Fix (Infeasible)" status.