Swapping Fragments instead of replacing ?

Question

I am trying to create a bottom navigation menu similar to WhatsApp, Viber etc. where I am switching between fragments. I got it somewhat working fragmentManager replacing the fragments, but as it turned out this re-creates the replaced fragments when I want to come back to one of the menu pages I have previously visited, changed etc.

 @Override
    public boolean onNavigationItemSelected(@NonNull MenuItem item) {
        Fragment fragment = null;

        switch (item.getItemId()) {
            case R.id.navigation_discover:
                fragment = findFragment(RPageFragment.getTAG());
                if(fragment == null){
                    fragment = RPageFragment.newInstance();
                    mFragmentManager.beginTransaction().add(R.id.fragment_container, fragment, fragment.getTag()).commit();
                }
                break;

            case R.id.navigation_booked:

                fragment = findFragment(MapViewFragment.getTAG());
                if(fragment == null){
                    fragment = MapViewFragment.newInstance();
                    mFragmentManager.beginTransaction().add(R.id.fragment_container, fragment, fragment.getTag()).commit();

                }
                break;

            case R.id.navigation_me:
                fragment = findFragment(ProfilePageFragment.getTAG());
                if(fragment == null){
                    fragment = ProfilePageFragment.newInstance();
                    mFragmentManager.beginTransaction().add(R.id.fragment_container, fragment, fragment.getTag()).commit();
                }
                break;
        }
        //Invalid menu option
        if (fragment == null)
            return false;

        mFragmentManager.beginTransaction().replace(R.id.fragment_container,fragment).commit();
        return true;
    }

Is there any way to swap the fragments while preserving their view, state etc. similar to the way Whatsapp works ? (For example I have a mapView Fragment and I would like when I come back to it, to be showing the way I left it instead of recreating the mapView)

Might be easier to use already existing solution https://github.com/ncapdevi/FragNav — Petr Kubáč, Dec 06 '18 at 14:48

score 1 · Answer 1 · answered Dec 06 '18 at 14:58

You can use How to implement a ViewPager with different Fragments / Layouts

You can simply check if fragment object null like below exaple:

case R.id.navigation_me:
        fragment = findFragment(ProfilePageFragment.getTAG());
        if (fragment == null) {
            mFragmentManager.beginTransaction().show(fragment);
        } else {
            fragment = ProfilePageFragment.newInstance();
            mFragmentManager.beginTransaction().add(R.id.fragment_container, fragment, fragment.getTag()).commit();
        }

        // and you can hide all other fragments here with
        fragmentRPage = findFragment(RPageFragment.getTAG());
        if (fragmentRPage == null) {
            mFragmentManager.beginTransaction().hide(fragmentRPage);
        }
        fragmentMapView = findFragment(MapViewFragment.getTAG());
        if (fragmentMapView == null) {
            mFragmentManager.beginTransaction().hide(fragmentMapView);
        }
        //... and hide other fragments

        break;

Swapping Fragments instead of replacing ?

1 Answers1