Callback when Fragment is replaced and when it is visible again

Question

I've been researching this topic but so far no luck. Basically I'm replacing a fragment (A) with another one (B) using FragmentTransaction.replace. In this other fragment (B) I have a 'Cancel' button in the toolbar which when pressed pops back to the previous transaction (A) by calling getActivity().getSupportFragmentManager().popBackStackImmediate().

The problem is I need to update the Activity toolbar to display a different title when I'm showing fragment A and fragment B. I can't seem to find a method which gets called in fragment A whenever I go from A -> B -> A to inform me that it is visible again. The idea is to set the toolbar title in this callback which I cannot seem to find.

Can anyone point me in the right direction please?

Cheers.

Edit:

Method I call to replace the fragment with another one is as follows:

public static void replaceFragment(FragmentActivity parentActivity, int fragmentToReplaceId, Fragment withFragment, Integer enterAnim, Integer exitAnim)
{
    FragmentManager         fragmentManager;
    FragmentTransaction     transaction;

    fragmentManager = parentActivity.getSupportFragmentManager();
    transaction     = fragmentManager.beginTransaction();

    if (    (null != enterAnim) &&
            (null != exitAnim)  )
    {
        transaction.setCustomAnimations(enterAnim, exitAnim);
    }

    transaction.replace(fragmentToReplaceId, withFragment);
    transaction.addToBackStack(null);
    transaction.commit();
}

Answer 1

You can inform by overriding method onResume() in fragment and sending the message to activity or changing the Toolbar directly.

@Override
public void onResume() {
    super.onResume();

    ((AppCompatActivity) getActivity()).getSupportActionBar().setTitle("Title");
}

Answer 2

In one activity, when replace A ---> B (A and B both are fragments), can use this call-back:

 @Override
 public void onAttachFragment(Fragment fragment) {

 }