The notifyDataSetChanged method does no update the RecyclerView layout

Question

I have created a nested RecyclerView. I fetch data from firebase, then I insert it into one RecyclerView which uses another RecyclerView. In my fragment the code is:

    private Map<Character,List<QueryDocumentSnapshot>> carsDocuments;
    private DocumentReference connectedGroupDocumentRef;

    private RecyclerView carsRecyclerViewCards;
    private CarDetailsCardAdapter cardsAdapter;

    private View fragmentView;

    public CarsDetailsFragment() {}

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        fragmentView = inflater.inflate(R.layout.fragment_cars_details, container, false);

        // On add new car click
        FloatingActionButton addNewCarFab = (FloatingActionButton) fragmentView.findViewById(R.id.fab_add_new_car);
        addNewCarFab.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View view) {
                Intent intent = new Intent(getActivity(), AddNewCar.class);
                fragmentView.getContext().startActivity(intent);
            }
        });

        carsDocuments = new HashMap<>();
        carsRecyclerViewCards = (RecyclerView) fragmentView.findViewById(R.id.rv_car_details_cards);
        connectedGroupDocumentRef = getConnectedGroupReference();
        connectedGroupDocumentRef.collection("cars").get().addOnCompleteListener(new OnCompleteListener<QuerySnapshot>() {

            @Override
            public void onComplete(@NonNull Task<QuerySnapshot> task) {
                if (task.isSuccessful()) {
                    RelativeLayout emptyView = fragmentView.findViewById(R.id.cars_details_empty_view);
                    if (task.getResult() == null || task.getResult().isEmpty()) {
                        emptyView.setVisibility(View.VISIBLE);
                        carsRecyclerViewCards.setVisibility(View.GONE);
                    } else {
                        for (QueryDocumentSnapshot document : task.getResult()) {
                            char letter = getFirstLetter(document.getString("type"));
                            List<QueryDocumentSnapshot> carsList = carsDocuments.get(letter);
                            if (carsList == null) {
                                carsList = new ArrayList<>();
                                carsList.add(document);
                                carsDocuments.put(letter, carsList);
                            } else {
                                carsList.add(document);
                            }
                        }
                        emptyView.setVisibility(View.GONE);
                        carsRecyclerViewCards.setVisibility(View.VISIBLE);
                        cardsAdapter = new CarsCardAdapter(getActivity(), carsDocuments);
                        carsRecyclerViewCards.setLayoutManager(new LinearLayoutManager(getActivity()));
                        carsRecyclerViewCards.setAdapter(cardsAdapter);
                        setRecyclerViewListener();
                    }
                }
            }
        });
    }


    private void setRecyclerViewListener() {
          connectedGroupDocumentRef.collection("cars").addSnapshotListener(new EventListener<QuerySnapshot>() {

            @Override
            public void onEvent(@Nullable QuerySnapshot value,
                                @Nullable FirebaseFirestoreException e) {
                if (e != null) {
                    Log.d(this.getClass().getName(), "addSnapshotListener:failure", e);
                    return;
                }

                carsDocuments.clear();
                for (QueryDocumentSnapshot document : value) {
                    char letter = getFirstLetter(document.getString("full_name"));
                    List<QueryDocumentSnapshot> carsList = carsDocuments.get(letter);
                    if (carsList == null) {
                        carsList = new ArrayList<>();
                        carsList.add(document);
                        carsDocuments.put(letter, carsList);
                    } else {
                        carsList.add(document);
                    }
                }
                System.out.println("I'm HERE");
                cardsAdapter.notifyDataSetChanged();
                //carsRecyclerViewCards.invalidate(); 
            }
        });
    }

In the CarsCardAdapter class:

public class CarsCardAdapter extends RecyclerView.Adapter<CarsCardAdapter.ViewHolder> {
    private Map<Character, List<QueryDocumentSnapshot>> carsDocuments;
    private Character[] carsLetters;
    private Activity activity;

    private UsersAdapter adapterMember;

    public class ViewHolder extends androidx.recyclerview.widget.RecyclerView.ViewHolder {
        private TextView textLetter;
        private RecyclerView recyclerViewUsers;

        public ViewHolder(@NonNull View itemView) {
            super(itemView);
            textLetter = itemView.findViewById(R.id.cars_details_letter);
            recyclerViewUsers = itemView.findViewById(R.id.car_details_users);
        }
    }

    CarsCardAdapter(Activity activity, Map<Character,List<QueryDocumentSnapshot>> carsDocuments) {
        this.activity = activity;
        if (carsDocuments != null) {
            this.carsDocuments = carsDocuments;
            this.carsLetters = carsDocuments.keySet().toArray(new Character[0]);
        }
    }

    public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        return new ViewHolder(LayoutInflater.from(parent.getContext()).inflate(R.layout.adapter_car_cards, parent, false));
    }

    public void onBindViewHolder(ViewHolder holder, int position) {
        final char letter = this.carsLetters[position];
        final List<QueryDocumentSnapshot> carsList = carsDocuments.get(letter);
        holder.textLetter.setText(String.valueOf(letter));
        adapterMember = new UsersAdapter(activity,carsList);
        holder.recyclerViewUsers.setLayoutManager(new LinearLayoutManager(this.activity));
        holder.recyclerViewUsers.setAdapter(this.adapterMember);
    }

    public int getItemCount() {
        return this.carsLetters.length;
    }
}

And the important method is setRecyclerViewListener which updates the RecyclerView once the database collection is changed. As you can see I remove the carsDocuments and insert all of the reports. Then I update the adapter by calling notifyDataSetChanged . Also tried invalidate . I know for sure that I get into the listener because I'm HERE is printed to the log. Also note that documentRef.collection("cars").get()... is being executed in the onCreateView of the my fragment. the What could be the issue?

Answer 1

First of all, add this:

carsRecyclerViewCards.setVisibility(View.VISIBLE);
                    cardsAdapter = new CarsCardAdapter(getActivity(), carsDocuments);
                    carsRecyclerViewCards.setLayoutManager(new LinearLayoutManager(getActivity()));
                    carsRecyclerViewCards.setAdapter(cardsAdapter);

Inside your setRecyclerViewListener(); like u did in the addOnSuccessListener

Then delete this:

   connectedGroupDocumentRef.collection("cars").get().addOnCompleteListener(new OnCompleteListener<QuerySnapshot>() {

        @Override
        public void onComplete(@NonNull Task<QuerySnapshot> task) {
            if (task.isSuccessful()) {
                RelativeLayout emptyView = fragmentView.findViewById(R.id.cars_details_empty_view);
                if (task.getResult() == null || task.getResult().isEmpty()) {
                    emptyView.setVisibility(View.VISIBLE);
                    carsRecyclerViewCards.setVisibility(View.GONE);
                } else {
                    for (QueryDocumentSnapshot document : task.getResult()) {
                        char letter = getFirstLetter(document.getString("type"));
                        List<QueryDocumentSnapshot> carsList = carsDocuments.get(letter);
                        if (carsList == null) {
                            carsList = new ArrayList<>();
                            carsList.add(document);
                            carsDocuments.put(letter, carsList);
                        } else {
                            carsList.add(document);
                        }
                    }
                    emptyView.setVisibility(View.GONE);
                    carsRecyclerViewCards.setVisibility(View.VISIBLE);
                    cardsAdapter = new CarsCardAdapter(getActivity(), carsDocuments);
                    carsRecyclerViewCards.setLayoutManager(new LinearLayoutManager(getActivity()));
                    carsRecyclerViewCards.setAdapter(cardsAdapter);
                    setRecyclerViewListener();
                }
            }
        }
    });

And put this

 setRecyclerViewListener();

In its place in onCreate