How to add tag to Fragment Transaction?

Question

I'm adding a Fragment to my Activity like this:

getSupportFragmentManager()
            .beginTransaction()              
            .add(R.id.frame_container, fragment)
            .setTransition(FragmentTransaction.TRANSIT_FRAGMENT_OPEN)
            .addToBackStack(fragment.getClass().getName())
            .commit();

But when I want to find the Fragment using a FragmentManager it's returning null:

 Fragment oldFragment = (Fragment) getSupportFragmentManager().findFragmentByTag(fragment.getClass().getName());

Answer 1

You try to find it by tag, but you haven't given it any tag

if you want to give it a tag, do it like this

getSupportFragmentManager()
        .beginTransaction()              
        .add(R.id.frame_container, fragment, "tagABC")
        .setTransition(FragmentTransaction.TRANSIT_FRAGMENT_OPEN)
        .addToBackStack(fragment.getClass().getName())
        .commit();

and then you can get it with

Fragment oldFragment = (Fragment) getSupportFragmentManager().findFragmentByTag("tagABC");

BTW, you should correct your question title, the problem has nothing related to backstack.