Fragment re-created on bottom navigation view item selected

Question

Following is my code for bottom navigation view item selected

bottomNavigationView.setOnNavigationItemSelectedListener(new BottomNavigationView.OnNavigationI         


        

Answer 1

With support library v26 you can do this

FragmentTransaction fragmentTransaction = mFragmentManager.beginTransaction();

Fragment curFrag = mFragmentManager.getPrimaryNavigationFragment();
if (curFrag != null) {
    fragmentTransaction.detach(curFrag);
}

Fragment fragment = mFragmentManager.findFragmentByTag(tag);
if (fragment == null) {
    fragment = new YourFragment();
    fragmentTransaction.add(container.getId(), fragment, tag);
} else {
    fragmentTransaction.attach(fragment);
}

fragmentTransaction.setPrimaryNavigationFragment(fragment);
fragmentTransaction.setReorderingAllowed(true);
fragmentTransaction.commitNowAllowingStateLoss();

Answer 2

This seemed to work well for me. Instead of attaching and detaching, i use show or hide to maintain fragment state.

    public void changeFragment(Fragment fragment, String tagFragmentName) {

        FragmentManager mFragmentManager = getSupportFragmentManager();
        FragmentTransaction fragmentTransaction = mFragmentManager.beginTransaction();

        Fragment currentFragment = mFragmentManager.getPrimaryNavigationFragment();
        if (currentFragment != null) {
            fragmentTransaction.hide(currentFragment);
        }

        Fragment fragmentTemp = mFragmentManager.findFragmentByTag(tagFragmentName);
        if (fragmentTemp == null) {
            fragmentTemp = fragment;
            fragmentTransaction.add(R.id.frame_layout, fragmentTemp, tagFragmentName);
        } else {
            fragmentTransaction.show(fragmentTemp);
        }

        fragmentTransaction.setPrimaryNavigationFragment(fragmentTemp);
        fragmentTransaction.setReorderingAllowed(true);
        fragmentTransaction.commitNowAllowingStateLoss();
    }

And this is how i use it

     private void initViews() {
        BottomNavigationView bottomNavigationView = findViewById(R.id.navigation);
        bottomNavigationView.setOnNavigationItemSelectedListener
                (new BottomNavigationView.OnNavigationItemSelectedListener() {
                    @Override
                    public boolean onNavigationItemSelected(@NonNull MenuItem item) {
                        Fragment selectedFragment = null;
                        switch (item.getItemId()) {
                            case R.id.explore:
                                changeFragment(new ExploreFragment(), ExploreFragment.class
                                        .getSimpleName());
                                toggleViews(true, "");
                                break;
                            case R.id.favorite:
                                changeFragment(new FavoriteFragment(), FavoriteFragment.class
                                        .getSimpleName());
                                toggleViews(false, "Favorites");
                                break;
                            case R.id.venue:
                                changeFragment(new VenueFragment(), VenueFragment.class.getSimpleName());
                                toggleViews(false, "Venues");
                                break;
                            case R.id.profile:
                                changeFragment(new ProfileFragment(), ProfileFragment.class
                                        .getSimpleName());
                                toggleViews(false, "Profile");
                                break;
                        }
                        return true;
                    }
                });

        //Manually displaying the first fragment - one time only
        changeFragment(new ExploreFragment(), ExploreFragment.class
                .getSimpleName());

    }

Answer 3

I wrote an Extension function in Kotlin for the same.

fun FragmentManager.switch(containerId: Int, newFrag: Fragment, tag: String) {

var current = findFragmentByTag(tag)
beginTransaction()
    .apply {

        //Hide the current fragment
        primaryNavigationFragment?.let { hide(it) }

        //Check if current fragment exists in fragmentManager
        if (current == null) {
            current = newFrag
            add(containerId, current!!, tag)
        } else {
            show(current!!)
        }
    }
    .setTransition(FragmentTransaction.TRANSIT_FRAGMENT_OPEN)
    .setPrimaryNavigationFragment(current)
    .setReorderingAllowed(true)
    .commitNowAllowingStateLoss()
}

Answer 4

Try this :

bottomNavigationView.setOnNavigationItemSelectedListener(new BottomNavigationView.OnNavigationItemSelectedListener() {
                @Override
                public boolean onNavigationItemSelected(@NonNull MenuItem item) {
                    Fragment fragment = null;
                    Fragment currentFragment = getSupportFragmentManager().findFragmentById(R.id.container);
                    switch (item.getItemId()) {
                        case R.id.action_one:
                            // Switch to page one
                            if (!(currentFragment instanceof FragmentA)) {
                                fragment = FragmentA.newInstance();
                            }
                            break;
                        case R.id.action_two:
                            // Switch to page two
                            if (!(currentFragment instanceof FragmentB)) {
                                fragment = FragmentB.newInstance();
                            }
                            break;
                        case R.id.action_three:
                            // Switch to page three
                            if (!(currentFragment instanceof FragmentC)) {
                                fragment = FragmentC.newInstance();
                            }
                            break;
                    }
                    getSupportFragmentManager().beginTransaction().replace(R.id.container, fragment, "TAG").commit();
                    return true;
                }
            });

That will get the current fragment in your container and if you click again on this fragment that will not re add the fragment.

Answer 5

Be careful when using replace. Even if providing a fragment that already exists in memory, replace will restart the fragment's lifecycle. To avoid a restart, the transaction object's methods includes add, show, and hide, which can be used to show the correct fragment without restarting it.

private fun switchFragment(selectedTabIndex: Int) {
    val previousTabIndex = this.currentTabIndex
    this.currentTabIndex = selectedTabIndex

    val transaction = supportFragmentManager.beginTransaction()
    val tag = fragments[this.currentTabIndex].tag

    // if the fragment has not yet been added to the container, add it first
    if (supportFragmentManager.findFragmentByTag(tag) == null) {
        transaction.add(R.id.container, fragments[this.currentTabIndex], tag)
    }

    transaction.hide(fragments[previousTabIndex])
    transaction.show(fragments[this.currentTabIndex])
    transaction.commit()
}

Answer 6

How To stop recreating Fragment when it is Already Visible Using BottomNavigationView

Step 1--

     @Override
public boolean onNavigationItemSelected(@NonNull MenuItem item) {
    Fragment fragment = null;
    String valuestring;      
    **if (item.getItemId() == lastSelectedItemId) { // added this
        Log.e( "both id is same","LULL" );
        return true;
    }**
    switch (item.getItemId()) {
       case R.id.navigation_category:
      SetActioBarText( getString( R.string.label_actionbar_categories ) );
            fragment = new CategoryFragment();
            valuestring = "category";
            break;
        case R.id.navigation_favourite:
     SetActioBarText( getString( R.string.label_actionbar_favourites ) );
            fragment = new FavouriteFragment();
            valuestring = "favourites";
            break;
        default:
            throw new IllegalStateException( "Unexpected value: " +                  menuItem.getItemId() );
    }
    return loadFragment( fragment, valuestring ,menuItem);
}

Now Step 2---

    private boolean loadFragment(Fragment fragment, String argument,MenuItem item) {
  
    if (fragment != null) {
       
        transaction = fragmentManager.beginTransaction();
        transaction.addToBackStack( argument );
        transaction.setTransition( FragmentTransaction.TRANSIT_FRAGMENT_FADE );
        transaction.replace( R.id.frame_container, fragment,                         "demofragment").commitAllowingStateLoss();

     lastSelectedItemId= item.getItemId();
    
        return true;
    }
    return false;
}