//BaseActivity
private BottomNavigationView.OnNavigationItemSelectedListener navigationItemSelectedListener = new BottomNavigationView.OnNavigationItemSelectedListener() {
        @Override
        public boolean onNavigationItemSelected(@NonNull MenuItem item) {
            baseViewModel.navButtonPressed(BaseActivity.this, item.getItemId());
            return true;
        }
    };


//BaseViewModel
public void navButtonPressed(Context context, int itemId) {
        switch(itemId) {
            case R.id.bottomNav_discover:
                ((AppCompatActivity) context).getSupportFragmentManager().beginTransaction().replace(R.id.base_fragment_container, new DiscoverFragment()).commit();
            break;
            case R.id.bottomNav_library:
                ((AppCompatActivity) context).getSupportFragmentManager().beginTransaction().replace(R.id.base_fragment_container, new LibraryFragment()).commit();
            break;
            case R.id.bottomNav_community:
                ((AppCompatActivity) context).getSupportFragmentManager().beginTransaction().replace(R.id.base_fragment_container, new CommunityFragment()).commit();
            break;
            case R.id.bottomNav_personal:
                ((AppCompatActivity) context).getSupportFragmentManager().beginTransaction().replace(R.id.base_fragment_container, new PersonalFragment()).commit();
            break;
        }
    }