How to find the fragment in back stack and just show it in android

Question

I have a Activity where I load 3 fragments one after another

• FragmentA
• FragmentB
• FragmentC

Flow is Like this I have used Adding fragment one above another

Start-Activity -----> Load FragmentA ----> Load FragmentB ----> Load FragmentC

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What I am trying to do now is:

Now assuming now FragmentC is the top fragment shown

I want to find the FragmentA from the stack and just show it instead of creating a fragmentA all over again

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Code I have used to add fragmentA is for Example:

            Fragment fragment = null;
            FragmentTransaction fragmentTransaction = null;
            fragment = new FragmentA();
            fragmentTransaction = fragmentManager.beginTransaction();
            fragmentTransaction.addToBackStack(FragmentA.class.getSimpleName());
            fragmentTransaction.setCustomAnimations(android.R.anim.fade_in, android.R.anim.fade_out);
            fragmentTransaction.add(R.id.container, fragment, FragmentA.class.getSimpleName());

            if(fragment!=null && fragmentTransaction!=null){
                fragmentTransaction.commitAllowingStateLoss();
            }

Answer 1

Look at FragmentManager.getBackStackEntryAt method, from there you can go back to any fragment of your history…

Answer 2

Loop through the back stack entries, meanwhile, if you find any matching Fragment by id or tag, just pop back stack inclusive with fragment A's name/tag so that the fragment A is just displayed rather than adding once again.

Answer 3

You are giving a tag, fragmentTransaction.addToBackStack(FragmentA.class.getSimpleName()); to the transaction , you can use the same tag to find the fragment in the backstack, before creating a new frgament, check the backstack for the fragment using findFragmentByTag on the fragment manager, if it exist, the method returns the fragment otherwise null

Answer 4

The example code to retrieve a fragment by Tag would look like this

FragmentA frA = getSupportFragmentManager().findFragmentByTag(FragmentA.class.getSimpleName()); 

and if it's not null you can reuse it in your container

if(frA != null) {
   FragmentTransaction fragmentTransaction = getSupportFragmentManager.beginTransaction();
   fragmentTransaction.setCustomAnimations(android.R.anim.fade_in, android.R.anim.fade_out);
   //you could add this transactionn to backstack again here if you want to be able to pop it later
   fragmentTransaction.add(R.id.container, frA, FragmentA.class.getSimpleName());
} else {
   //if your fragment is null as it was destroyed previously you can create a new one here
}

Answer 5

try it!

val fm: FragmentManager? = fragmentManager
for (entry in 0 until fm.getBackStackEntryCount()) {
    Log.i(TAG, "Found fragment: " + fm.getBackStackEntryAt(entry).getId())
}