Java – How do I know if any fragment is active or visible?

I have three fragments A, B, and C in an activity, and the activity has a toolbar with a test View title.

Now, when I navigate from one fragment to another, I want to change the text of the TextView depending on the fragment displayed.

To do this, in fragments B and C, I took the toolbar and TextView of the main activity and changed its title like this:

        final Toolbar toolbar = (Toolbar) ((MainActivity) getActivity()).findViewById(R.id.toolbar);
    ((MainActivity) getActivity()).setSupportActionBar(toolbar);

TextView title = (TextView) getActivity().findViewById(R.id.textView_Title);
    title.setVisibility(View.VISIBLE);
    title.setText(R.string.profile);

This works great. But when I go back to the main fragment, I want to change the title again, but it doesn’t get changed.

I tried to set it in the onCreate method of the main activity, like this:

 @Override
public void onBackPressed() {

DashboardFragment test = (DashboardFragment) getSupportFragmentManager().findFragmentByTag("DASHBOARD_FRAGMENT");
    if (test != null && test.isVisible()) {
        DO STUFF

title = (TextView) findViewById(R.id.textView_Title);
        title.setVisibility(View.VISIBLE);
        title.setText(R.string.dashboardTitle);
    }
    else {
        Whatever
    }
     Do nothing if the back button is disabled.
    if (!mBackPressCancelled) {

if (getFragmentManager().getBackStackEntryCount() > 0) {
            getFragmentManager().popBackStackImmediate();
        }
        else {

super.onBackPressed();

}
    }
}

But with this, even if B fragment is visible, it will change its title to the main fragment title.

How do I do it. Please help. Thank you.

Edit:

Main fragment :

        fragmentManager = getSupportFragmentManager();
    DashboardFragment fragment1 = new DashboardFragment();
    Bundle bundle = new Bundle();
    fragment1.setArguments(bundle);
    fragmentManager.popBackStack(null,FragmentManager.POP_BACK_STACK_INCLUSIVE);
    fragmentManager.beginTransaction().replace(R.id.frame, fragment1, "DASHBOARD_FRAGMENT").commitAllowingStateLoss();

fragment :

                fragmentManager = ((MainActivity)(mContext)).getSupportFragmentManager();
                ProfileFragment fragment1 = new ProfileFragment();
                Bundle bundle = new Bundle();
                fragment1.setArguments(bundle);           
                fragmentManager.beginTransaction().add(R.id.frame, fragment1, "PROFILE_FRAGMENT").addToBackStack("B").commit();

B fragment

       fragmentManager = getActivity().getSupportFragmentManager();
            ProfileEditFragment fragment1 = new ProfileEditFragment();
            Bundle bundle = new Bundle();
            fragment1.setArguments(bundle);       
            fragmentManager.beginTransaction().add(R.id.frame, fragment1, "PROFILE_EDIT_FRAGMENT").addToBackStack("C").commit();

If you want to change the title of the Activity toolbar for a different fragment, instead of using interface.

Create an interface:

public interface OnFragmentTitleChangeListener {
    void onFragmentTitle(String strTitle);
}

Implement this interface in your activity

public class YourActivity extends AppCompatActivity implements OnFragmentTitleChangeListener
{
  TextView title;
  ......
  ......
   Initialize title in onCreate method
  ......
  ......
   Override this method
  public void onFragmentTitle(String strTitle) 
  {
      title.setText(strTitle);
  }

@Override
  public void onBackPressed() {
    FragmentManager fm = getSupportFragmentManager();

if (onBack(fm)) {
        return;
    }
    super.onBackPressed();
  }

private boolean onBack(FragmentManager fm) {
     if (fm != null) {
        if (fm.getBackStackEntryCount() > 0) {
            fm.popBackStack();
            return true;
        }
    }
    return false;
  }
}

After that, set the text from the fragment’s onResume method.

@Override
public void onResume() {
    super.onResume();
    ((OnFragmentTitleChangeListener) mContext).onFragmentTitle(getResources().getString(R.string.yourtext));
}