Android Up button with fragments not showing complete fragment-CodePudding

Hi I have an activity A with a button that sends to Activity B with ActionBar and up button enabled, this activity has tabs with fragments and a button that send to a new fragment C not related with the tabs. By clicking the back button, it is supposed to return to the tabs. The back button works and shows the tabs but not the contain. What I'm doing wrong? Here's some code. Thanks in advance. Activity B

public class BackActivity extends AppCompatActivity {

  
...

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_back);
        // get fragment manager

        myChildToolbar =(Toolbar)findViewById(R.id.my_child_toolbar2);
        setSupportActionBar(myChildToolbar);
        // Get a support ActionBar corresponding to this toolbar
        ActionBar ab = getSupportActionBar();

        // Enable the Up button
        ab.setDisplayHomeAsUpEnabled(true);

        FragmentTransaction ft = getSupportFragmentManager().beginTransaction();
               
       myChildToolbar.setTitle(R.string.menu_ver_lista);
       Bundle bundle=new Bundle();
           bundle.putInt(NuevoinformeFragment.INFORMESEL,datosRecuperados.getInt(NuevoinformeFragment.INFORMESEL));
                    
     bundle.putString(TabsFragment.ARG_MUESTRA,"true");
                    
     TabsFragment detailFragment = new TabsFragment();
                    detailFragment.setArguments(bundle);
                    ft.add(R.id.back_fragment, detailFragment);
                   


       ft.commit();
      }
    @Override
    public boolean onSupportNavigateUp() {
        onBackPressed();
        return false;
    }
  
}

Tabs fragment

   
    TabLayout tabs;
    ViewPager viewPager;
    private ListaDetalleViewModel mViewModel;
   
    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container,
                             @Nullable Bundle savedInstanceState) {
        View root = inflater.inflate(R.layout.fragment_lista_tabs, container, false);


        mViewModel = new ViewModelProvider(requireActivity()).get(ListaDetalleViewModel.class);


 
        return root;
    }

    @Override
    public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {

        Bundle bundle = getArguments();
       
        viewPager = view.findViewById(R.id.view_pager);

        tabs = view.findViewById(R.id.tabs);
        tabs.setupWithViewPager(viewPager);
 mViewModel.cargarPestañas(ciudadNombre).observe(getViewLifecycleOwner(), words -> {
          
            configureTabLayout();

        });

    }

    private void configureTabLayout() {

        SectionsPagerAdapter sectionsPagerAdapter = new SectionsPagerAdapter( getFragmentManager(),clientes, mViewModel,clientesplan);
        viewPager.setAdapter(sectionsPagerAdapter);
   
        viewPager.addOnPageChangeListener(new
                TabLayout.TabLayoutOnPageChangeListener(tabs));
        tabs.addOnTabSelectedListener(new
               TabLayout.OnTabSelectedListener() {
               @Override
               public void onTabSelected(TabLayout.Tab tab) {



                   viewPager.setCurrentItem(tab.getPosition());
               }

               @Override
               public void onTabUnselected(TabLayout.Tab tab) {

               }

               @Override
               public void onTabReselected(TabLayout.Tab tab) {

               }

           });
    }

}

CodePudding user response：

You're using the wrong FragmentManager when creating your SectionsPagerAdapter, you should be using getChildFragmentManager() here:

SectionsPagerAdapter sectionsPagerAdapter = new SectionsPagerAdapter(
   getFragmentManager(), // This is the problem
   clientes, mViewModel,clientesplan
);

getFragmentManager() actually refers to the FragmentManager that your TabsFragment has been added to - that's why that method was deprecated and replaced with getParentFragmentManager(), which is more explicit on what that FragmentManager means.

Whenever the fragment you create is fully contained in the layout of another fragment, it needs to be a child fragment by being added to the getChildFragmentManager(). This ensures that it moves through lifecycle states properly (such as getting its Views recreated when its parent has its Views recreated) and to ensure that the state of the fragments are saved and restored properly.