java.lang.IllegalStateException ConstraintLayout does not have a NavController set for a fragment

Question

I have an activity (main) with three fragments (first, second and third). I included the 3 fragments in my activity (activity_main.xml) by using <include layout="@layout/content_main"/>. The content_main.xml is using FragmentContainerView with id = nav_host_fragment. And this is my nav_graph.xml:

<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_graph"
    app:startDestination="@id/FirstFragment">

    <fragment
        android:id="@+id/FirstFragment"
        android:name="com.example.makegroups.FirstFragment"
        android:label="@string/first_fragment_label"
        tools:layout="@layout/fragment_first">

        <action
            android:id="@+id/action_FirstFragment_to_SecondFragment"
            app:destination="@id/SecondFragment" />
    </fragment>

    <fragment
        android:id="@+id/SecondFragment"
        android:name="com.example.makegroups.SecondFragment"
        android:label="@string/second_fragment_label"
        tools:layout="@layout/fragment_second">

        <action
            android:id="@+id/action_SecondFragment_to_FirstFragment"
            app:destination="@id/FirstFragment" />
        <action
            android:id="@+id/action_SecondFragment_to_ThirdFragment"
            app:destination="@id/ThirdFragment" />
    </fragment>

    <fragment
        android:id="@+id/ThirdFragment"
        android:name="com.example.makegroups.ThirdFragment"
        android:label="@string/third_fragment_label"
        tools:layout="@layout/fragment_third">

        <action
            android:id="@+id/action_ThirdFragment_to_FirstFragment"
            app:destination="@id/FirstFragment" />
    </fragment>
</navigation>

I have a floatingactionbuttonin my activity (first fragmentstarts first) and when I click on it, I open the third fragment. On the third fragment I have a button (next) to navigate to the first fragment, and when I click on it, I am back to first fragment using:

Fragment frg = new FirstFragment();
FragmentManager fm = requireActivity().getSupportFragmentManager();

Now (while I am in the first fragment), I click on the button next(another button to navigate to the second fragment), then the app crashes. I found this error:

java.lang.IllegalStateException: View androidx.constraintlayout.widget.ConstraintLayout{c9572fa V.E...... ........ 0,0-1440,2112} does not have a NavController set

Why I am getting this error? -I tried these suggestions here, without success.

I am using Java.

EDIT: Read the last comment with @Zain to know why I got the error.

Answer 1

Bu using Navigation Architecture components, The NavController is the responsible for fragment transaction and managing the back stack instead of the Support FragmentManager.

So, instead of making tranditional framgnet transactions with FragmentManager

You can move from ThridFragment to the first one by:

 Navigation.findNavController(requireView()).navigate(R.id.action_ThirdFragment_to_FirstFragment);

Where action_ThirdFragment_to_FirstFragment is the id of the action you defined in the navigation graph to move from ThridFragment to FirstFragment

UPDATE:

As discussed from comments, besides replacing FragmentManager by NavController in all actions; there is another issue:

Missing of action_FirstFragment_to_ThirdFragment action from the navigation graph.

Answer 2

when using the Navigation Component you should not handle the transactions yourself, instead you define the actions between each fragment and then access those directly like this

override fun onCreate(){
  val navController = this.findNavController()
  button.setOnClickListener{
     navController.navigate(R.id.action_FirstFragment_to_SecondFragment, null)
  }
}

and your nav_graph should be like this

<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_graph"
app:startDestination="@id/FirstFragment">

<fragment
    android:id="@+id/FirstFragment"
    android:name="com.example.makegroups.FirstFragment"
    android:label="@string/first_fragment_label"
    tools:layout="@layout/fragment_first">

    <action
        android:id="@+id/action_FirstFragment_to_SecondFragment"
        app:destination="@id/SecondFragment" />
</fragment>

<fragment
    android:id="@+id/SecondFragment"
    android:name="com.example.makegroups.SecondFragment"
    android:label="@string/second_fragment_label"
    tools:layout="@layout/fragment_second">

    <action
        android:id="@+id/action_SecondFragment_to_FirstFragment"
        app:destination="@id/FirstFragment" />
    <action
        android:id="@+id/action_SecondFragment_to_ThirdFragment"
        app:destination="@id/ThirdFragment" />
</fragment>

<fragment
    android:id="@+id/ThirdFragment"
    android:name="com.example.makegroups.ThirdFragment"
    android:label="@string/third_fragment_label"
    tools:layout="@layout/fragment_third">

    <action
        android:id="@+id/action_ThirdFragment_to_FirstFragment"
        app:destination="@id/FirstFragment" />
</fragment>

Answer 3

navController = Navigation.findNavController(activity, R.id.nav_host_fragment)

Answer 4

val navController = Navigation.findNavController(requireActivity(), R.id.fragment_container)
navigate.navigate(R.id.fragment)