How to add BackStackEntry to BackStack if not exists

Question

I've added custom keyboard to my Fragment and now I want to implement closing keyboard when on back pressed.

class CustomKeyboard
{
    public void init(Context context) {
        //...

        FragmentManager fragmentManager = ((Activity) context).getFragmentManager();
        boolean fragmentPopped = fragmentManager.popBackStackImmediate(TAG, 0);
        if (!fragmentPopped) {
            FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
            fragmentTransaction.addToBackStack(TAG);
            fragmentTransaction.commit();
        }
    }
}

The problem is init calls every time when screen rotated because I create CustomKeyboard in public void onActivityCreated(final Bundle savedInstanceState)

fragmentPopped=false every time, so CustomKeyboard may be added to BackStack more than one time.

My question:
Is it possible to add BackStackEntry to BackStack if not exists without using getBackStackEntryCount() method?

https://developer.android.com/reference/android/app/FragmentManager.html#POP_BACK_STACK_INCLUSIVE — IntelliJ Amiya, Oct 01 '16 at 08:55
you want your question answered directly or want to solve your problem of multiple calls? — Elltz, Oct 03 '16 at 03:22
I believe there is a bug somewhere in your code. You should post some more code. — Mimmo Grottoli, Oct 06 '16 at 19:35
You want to say that you have to check backstack entry with some other method other than getBackStackEntryCount() and if it is 0 then add fragment Right ? — Ashish Shukla, Oct 07 '16 at 06:43

score 2 · Answer 1 · answered Oct 07 '16 at 06:12

Try the below updated code.

public void init(Context context) { 

    FragmentManager fragmentManager = ((Activity) context).getFragmentManager();
    boolean fragmentPopped = fragmentManager.popBackStack(TAG, 0);
    if (!fragmentPopped) {
        FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
        fragmentTransaction.addToBackStack(TAG);
        fragmentTransaction.commit();
    }
}

score 2 · Answer 2 · answered Oct 07 '16 at 11:06

You can do something like this :

     FragmentManager fm= getSupportFragmentManager();

    if(fm!=null && getSupportFragmentManager().getFragments()!=null) {

        boolean fragmentPopped = fm.popBackStackImmediate(TAG, 0);

        if (!fragmentPopped && getSupportFragmentManager().getFragments().size() == 0) {

            FragmentTransaction ft = fm.beginTransaction();
            ft.addToBackStack(TAG);
            ft.commit();
        }
    }

Also You can clean your Backstack first like this and then replace your fragment :

  private void cleanBackStack() {
    FragmentManager fm = getSupportFragmentManager();
    if (fm != null && fm.getFragments() != null) {
        if (fm.getFragments().size() > 1) {

            for (int entry = 0; entry < fm.getFragments().size(); entry++) {
                fm.popBackStackImmediate();
            }
        } else if (fm.getFragments().size()==1){

            fm.popBackStack();
        }else if(fm.getFragments().size()==0){
              //REPLACE YOUR FRAGMENT
        }
    }
}

How to add BackStackEntry to BackStack if not exists

2 Answers2