Why still in Fragment A although already navigate to Fragment B Navigation Component?

Question

I have 2 fragment, LoginFragment and SignUpFragment.When in SignUpFragment, click on Android back button at the bottom,it navigate to LoginFragment.

This is the code for doing so:

SignUpFragment.java

@Override
public void onViewCreated(@NonNull final View view, @Nullable Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);
        requireActivity().getOnBackPressedDispatcher().addCallback(new OnBackPressedCallback(true) {
            @Override
            public void handleOnBackPressed() {
                NavController navController = Navigation.findNavController(view);
                navController.popBackStack(R.id.signUpFragment,true);
                navController.navigate(R.id.loginFragment);
            }
        });
}

So this work as expected,I can go back to LoginFragment.java when click the back button in SignUpFragment.java.

Problem:

The problem now is,when I in LoginFragment,I click on the Android back button at the bottom again,I having this error:

 java.lang.IllegalStateException: View android.widget.RelativeLayout{3be3bdc V.E...... ......ID 0,0-1080,1962 #7f0a017d app:id/root_layout} does not have a NavController set
    at androidx.navigation.Navigation.findNavController(Navigation.java:84)
    at com.company.ui.user.SignUpFragment$3.handleOnBackPressed(SignUpFragment.java:128) //WHY THIS LINE??
    at androidx.activity.OnBackPressedDispatcher.onBackPressed(OnBackPressedDispatcher.java:189)
    at androidx.activity.ComponentActivity.onBackPressed(ComponentActivity.java:286)

As you can see,the error shown is said the error cause by handleOnBackPressed(SignUpFragment.java:128),means that it caused by handleOnBackPressed() function inside SignUpFragment.java.

But in reality I click the back button when I in LoginFragment.java.And inside LoginFragment.java doesnt have any handleOnBackPressed() function.

I totally having no idea why this behavior could happened?.

Question:

Why is this could happened? What causing this?? And how to solve this??

Answer 1

requireActivity().getOnBackPressedDispatcher().addCallback(new OnBackPressedCallback(true) {

Should be

requireActivity().getOnBackPressedDispatcher().addCallback(getViewLifecycleOwner(), new OnBackPressedCallback(true) {