get the latest fragment in backstack

Question

How can I get the latest fragment instance added in backstack (if I do not know the fragment tag & id)?

FragmentManager fragManager = activity.getSupportFragmentManager();
FragmentTransaction fragTransacion = fragMgr.beginTransaction();

/****After add , replace fragments 
  (some of the fragments are add to backstack , some are not)***/

//HERE, How can I get the latest added fragment from backstack ??

Answer 1

I personnaly tried many of those solutions and ended up with this working solution:

Add this utility method that will be used several times below to get the number of fragments in your backstack:

protected int getFragmentCount() {
    return getSupportFragmentManager().getBackStackEntryCount();
}

Then, when you add/replace your fragment using FragmentTransaction method, generate a unique tag to your fragment (e.g.: by using the number of fragments in your stack):

getSupportFragmentManager().beginTransaction().add(yourContainerId, yourFragment, Integer.toString(getFragmentCount()));

Finally, you can find any of your fragments in your backstack with this method:

private Fragment getFragmentAt(int index) {
    return getFragmentCount() > 0 ? getSupportFragmentManager().findFragmentByTag(Integer.toString(index)) : null;
}

Therefore, fetching the top fragment in your backstack can be easily achieved by calling:

protected Fragment getCurrentFragment() {
    return getFragmentAt(getFragmentCount() - 1);
}

Hope this helps!

Answer 2

You can use the getName() method of FragmentManager.BackStackEntry which was introduced in API level 14. This method will return a tag which was the one you used when you added the Fragment to the backstack with addTobackStack(tag).

int index = getActivity().getFragmentManager().getBackStackEntryCount() - 1
FragmentManager.BackStackEntry backEntry = getFragmentManager().getBackStackEntryAt(index);
String tag = backEntry.getName();
Fragment fragment = getFragmentManager().findFragmentByTag(tag);

You need to make sure that you added the fragment to the backstack like this:

fragmentTransaction.addToBackStack(tag);

Answer 3

FragmentManager.findFragmentById(fragmentsContainerId) 

function returns link to top Fragment in backstack. Usage example:

    fragmentManager.addOnBackStackChangedListener(new OnBackStackChangedListener() {
        @Override
        public void onBackStackChanged() {
            Fragment fr = fragmentManager.findFragmentById(R.id.fragmentsContainer);
            if(fr!=null){
                Log.e("fragment=", fr.getClass().getSimpleName());
            }
        }
    });

Answer 4

The answer given by deepak goel does not work for me because I always get null from entry.getName();

What I do is to set a Tag to the fragment this way:

ft.add(R.id.fragment_container, fragmentIn, FRAGMENT_TAG);

Where ft is my fragment transaction and FRAGMENT_TAG is the tag. Then I use this code to get the fragment:

Fragment prev_fragment = fragmentManager.findFragmentByTag(FRAGMENT_TAG);

Answer 5

Just took @roghayeh hosseini (correct) answer and made it in Kotlin for those here in 2017 :)

fun getTopFragment(): Fragment? {
    supportFragmentManager.run {
        return when (backStackEntryCount) {
            0 -> null
            else -> findFragmentByTag(getBackStackEntryAt(backStackEntryCount - 1).name)
        }
    }
}

*This should be called from inside an Activity.

Enjoy :)

Answer 6

Keep your own back stack: myBackStack. As you Add a fragment to the FragmentManager, also add it to myBackStack. In onBackStackChanged() pop from myBackStack when its length is greater than getBackStackEntryCount.