<androidx.fragment.app.FragmentContainerView> vs <fragment> as a view for a NavHost

问题

When using androidx.fragment.app.FragmentContainerView as a navHost instead of a regular fragment app is not able to navigate to a destination after orientation change.

I get a following error: java.lang.IllegalStateException: no current navigation node

Is there a gotcha that I should know about to use it properly or is my way of using nav components is incorrect?

Simple activity xml with a view:

...
    <androidx.fragment.app.FragmentContainerView
        android:id="@+id/nav_host_fragment"
        android:name="androidx.navigation.fragment.NavHostFragment"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        app:defaultNavHost="true"
        app:layout_behavior="@string/appbar_scrolling_view_behavior"
        app:navGraph="@navigation/nav_simple" />
...

Navigation code:

<?xml version="1.0" encoding="utf-8"?>
<navigation xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/nav_legislator.xml"
    app:startDestination="@id/initialFragment">

    <fragment
        android:id="@+id/initialFragment"
        android:name="com.example.fragmenttag.InitialFragment"
        android:label="Initial Fragment"
        tools:layout="@layout/initial_fragment">
        <action
            android:id="@+id/action_initialFragment_to_destinationFragment"
            app:destination="@id/destinationFragment" />
    </fragment>
    <fragment
        android:id="@+id/destinationFragment"
        android:name="com.example.fragmenttag.DestinationFragment"
        android:label="Destination Fragment"
        tools:layout="@layout/destination_fragment" />

</navigation>

Here is a github repo where you can easily reproduce a bug: https://github.com/dmytroKarataiev/navHostBug

回答1:

The no current navigation node error occurs when there's no graph set and you attempt to call navigate(). If it only occurs when you're using FragmentContainerView and after a configuration change, then this would be related to this bug, which is fixed and scheduled for release with Navigation 2.2.0-rc03.

To work around this issue, you can either switch back to <fragment> or remove app:navGraph="@navigation/nav_simple" and instead call navController.setGraph(R.navigation.nav_simple).

来源：https://stackoverflow.com/questions/58737769/androidx-fragment-app-fragmentcontainerview-vs-fragment-as-a-view-for-a-navh