On Back press traversing through last two tabs not working properly in BottomNavigationView?

Question

On click of back button, navigate to the previous tab that was opened. You will exit the app only by traversing through last two tabs you have opened.how to achieve

Answer 1

Update onBackPressed() as below:

@Override
public void onBackPressed() {

    if (mSelectedItem == R.id.menu_notifications) {

        MenuItem searchItem = mBottomNav.getMenu().getItem(1);
        selectFragment(searchItem);
        mBottomNav.setSelectedItemId(searchItem.getItemId());

    } else if (mSelectedItem == R.id.menu_search) {

        MenuItem homeItem = mBottomNav.getMenu().getItem(0);
        selectFragment(homeItem);
        mBottomNav.setSelectedItemId(homeItem.getItemId());

    } else {
        super.onBackPressed();
    }
}

UPDATE:

Try to add all fragment transaction to the back stack and pop when back pressed:

Try this:

public class MainActivity extends AppCompatActivity {
    private static final String SELECTED_ITEM = "arg_selected_item";

    private BottomNavigationView mBottomNav;
    private int mSelectedItem;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        mBottomNav = (BottomNavigationView) findViewById(R.id.navigation);
        mBottomNav.setOnNavigationItemSelectedListener(new BottomNavigationView.OnNavigationItemSelectedListener() {
            @Override
            public boolean onNavigationItemSelected(@NonNull MenuItem item) {
                selectFragment(item);
                return true;
            }
        });

        MenuItem selectedItem;
        if (savedInstanceState != null) {
            mSelectedItem = savedInstanceState.getInt(SELECTED_ITEM, 0);
            selectedItem = mBottomNav.getMenu().findItem(mSelectedItem);
        } else {
            selectedItem = mBottomNav.getMenu().getItem(0);
        }

        selectFragment(selectedItem);
    }

    @Override
    protected void onSaveInstanceState(Bundle outState) {
        outState.putInt(SELECTED_ITEM, mSelectedItem);
        super.onSaveInstanceState(outState);
    }

    @Override
    public void onBackPressed() {

        FragmentManager fragmentManager = getSupportFragmentManager();

        if (fragmentManager.getBackStackEntryCount() > 1) {
            fragmentManager.popBackStackImmediate();
        } else  {
            super.onBackPressed();
        }
    }

    private void selectFragment(MenuItem item) {

        Fragment frag = null;
        item.setCheckable(true);
        switch (item.getItemId()) {
            case R.id.menu_home:

                TabFragmentOne fragmentone = new TabFragmentOne();
                FragmentTransaction ft =  getSupportFragmentManager().beginTransaction();
                ft.replace(R.id.container, fragmentone);
                ft.addToBackStack(null);
                ft.commit();

                break;
            case R.id.menu_notifications:


                TabFragmentThree fragmentone_Three = new TabFragmentThree();
                FragmentTransaction ft_three =  getSupportFragmentManager().beginTransaction();
                ft_three.replace(R.id.container, fragmentone_Three);
                ft_three.addToBackStack(null);
                ft_three.commit();

                break;
            case R.id.menu_search:


                TabFragmentTwo tabFragmentTwo = new TabFragmentTwo();
                FragmentTransaction ft_two =  getSupportFragmentManager().beginTransaction();
                ft_two.replace(R.id.container,tabFragmentTwo);
                ft_two.addToBackStack(null);
                ft_two.commit();

                break;
        }

        // update selected item
        mSelectedItem = item.getItemId();

        updateToolbarText(item.getTitle());

        if (frag != null) {
            TabFragmentOne fragmentone = new TabFragmentOne();
            FragmentTransaction ft =  getSupportFragmentManager().beginTransaction();
            ft.replace(R.id.container, fragmentone);
            ft.commit();
        }
    }

    private void updateToolbarText(CharSequence text) {
        ActionBar actionBar = getSupportActionBar();
        if (actionBar != null) {
            actionBar.setTitle(text);
        }
    }
}