RecyclerView Items Duplicating when navigating through different Fragments, arraylist.clear() doesn´t work

Question

This is my first post here. I´m having trouble with a RecyclerView which I´m using into a fragment. I have two different fragments for a BottomNavigationMenu and the items duplicate everytime I get back to the fragment where the RecyclerView is in. I have tried using arraylist.clear(); as it is been suggested many times here but it doesn´t work. I have used the exact same code before using TabLayout with fragments instead of BottomNavigationMenu and it worked fine. the items didn´t duplicate at all.., I´m making a music library for an audio streaming app and I´m using realtime firebase to print the information for the RecyclerView onto the screen: if I use; if (audioFileArrayList == null) { loadData(). } it fixes the issue beacuse this way it doesn´t print the information twice but I don´t think this is a proper solution to this problem. It seems as if everytime I go back to the RecyclerView fragment the view doesn´t refresh but instead it prints everything again and again at the bottom...

This is the MainActivity:

public class MainActivity extends AppCompatActivity {

    ActivityMainBinding binding;
    BottomNavigationView bottomNavigationView;

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

        binding = ActivityMainBinding.inflate(getLayoutInflater());
        View view = binding.getRoot();
        setContentView(view);
        getSupportActionBar().hide(); //escondemos la action bar

        bottomNavigationView = binding.bottomNavigationID;
        getSupportFragmentManager().beginTransaction().replace(R.id.frame_layout_id, new BibliotecaFragment()).commit();

        bottomNavigationView.setOnItemSelectedListener(new NavigationBarView.OnItemSelectedListener() {
            @Override
            public boolean onNavigationItemSelected(@NonNull MenuItem item) {

                Fragment fragmentSeleccionado = null;

                switch (item.getItemId()) {
                    case R.id.biblioteca_ID:
                        fragmentSeleccionado = new BibliotecaFragment();
                        break;
                    case R.id.playlists_ID:
                        fragmentSeleccionado = new PlayListsFragment();
                        break;
                }
                getSupportFragmentManager().beginTransaction().replace(R.id.frame_layout_id, fragmentSeleccionado).commit();
                return true;
            }
        });
    }
}

This is the fragment for the library, as I said before if I use

if (audioFileArrayList == null) {
                loadData();
            }

it stops it from printing it twice.

public class BibliotecaFragment extends Fragment {

FragmentBibliotecaBinding binding;
RecyclerView recyclerView;
AudioFileAdapter audioFileAdapter;
static ArrayList<AudioFile> audioFileArrayList;

@Override
public View onCreateView(@NonNull LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
    binding = FragmentBibliotecaBinding.inflate(getLayoutInflater());

    recyclerView = binding.BibliotecaFragmentRecyclerViewID;
    recyclerView.setHasFixedSize(true);
    LinearLayoutManager manager = new LinearLayoutManager(getContext(), RecyclerView.VERTICAL, false);
    recyclerView.setLayoutManager(manager);
    audioFileAdapter = new AudioFileAdapter(getContext());
    recyclerView.setAdapter(audioFileAdapter);


    loadData();
    
    return binding.getRoot();
}

public void loadData() {

    DatabaseReference dbr = FirebaseDatabase.getInstance().getReference();

    dbr.child("biblioteca").addValueEventListener(new ValueEventListener() {
        @Override
        public void onDataChange(@NonNull DataSnapshot snapshot) {

            audioFileArrayList = new ArrayList<>();
            for (DataSnapshot data : snapshot.getChildren()) {

                AudioFile audioFile = data.getValue(AudioFile.class);
                audioFileArrayList.add(audioFile);
            }
            audioFileAdapter.setItems(audioFileArrayList);
            audioFileAdapter.notifyDataSetChanged();
        }

        @Override
        public void onCancelled(@NonNull DatabaseError error) {

        }
    });
}

}

This is my adapter:

public class AudioFileAdapter extends RecyclerView.Adapter<RecyclerView.ViewHolder> {

    private Context context;
    static ArrayList<AudioFile> audioFileList = new ArrayList<>();

    public AudioFileAdapter(Context ctx) {
        this.context = ctx;
    }

    public void setItems(ArrayList<AudioFile> audioFile) {
        audioFileList.addAll(audioFile);
    }

    @NonNull
    @Override
    public RecyclerView.ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        View view = LayoutInflater.from(context).inflate(R.layout.audio_item, parent, false);
        return new AudioFileViewHolder(view);
    }

    @Override
    public void onBindViewHolder(@NonNull RecyclerView.ViewHolder holder, @SuppressLint("RecyclerView") int position) {

        AudioFileViewHolder audioFileViewHolder = (AudioFileViewHolder) holder;
        AudioFile audioFile = audioFileList.get(position);

        audioFileViewHolder.txtArtist.setText(audioFile.getArtist());
        audioFileViewHolder.txtTitle.setText(audioFile.getTitle());
        Glide.with(context).load(audioFile.getImgURL()).into(audioFileViewHolder.imageViewPicture);

        holder.itemView.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Bundle bundle = new Bundle();
                bundle.putInt("posicion", position);
                Intent intent = new Intent(context, Reproductor.class);
                intent.putExtras(bundle);
                context.startActivity(intent);
            }
        });

        ((AudioFileViewHolder) holder).imageViewMenu.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                PopupMenu popupMenu = new PopupMenu(context, view);
                popupMenu.getMenuInflater().inflate(R.menu.audio_item_popup_menu, popupMenu.getMenu());
                popupMenu.show();

                popupMenu.setOnMenuItemClickListener((menuItem) -> {

                    switch (menuItem.getItemId()) {

                        case R.id.agregar_a_lista_ID: {

                            break;
                        }
                        case R.id.eliminar_de_biblioteca_ID: {
                            eliminar(position);
                            break;
                        }
                    }
                    return true;
                });
            }
        });
    }

    public void eliminar(int position) {

        String id = audioFileList.get(position).getId();

        DatabaseReference databaseReference = FirebaseDatabase.getInstance().getReference();
        Query delete = databaseReference.child("biblioteca").orderByChild("id").equalTo(id);

        delete.addListenerForSingleValueEvent(new ValueEventListener() {
            @Override
            public void onDataChange(DataSnapshot dataSnapshot) {
                audioFileList.clear(); // importante limpiar la lista cada vez que se elimina un item para que no se dupliquen en la parte de abajo...
                for (DataSnapshot data : dataSnapshot.getChildren()) {
                    data.getRef().removeValue();
                }
            }

            @Override
            public void onCancelled(DatabaseError databaseError) {
            }
        });
    }

    @Override
    public int getItemCount() {
        return audioFileList.size();
    }

    public interface ItemClickListener { //interfaz listener para RyclerView
        void onItemClick(AudioFile audioFile);
    }
}

My ViewHolder:

public class AudioFileViewHolder extends RecyclerView.ViewHolder {

    public TextView txtArtist, txtTitle;
    public ImageView imageViewPicture, imageViewMenu;

    public AudioFileViewHolder(@NonNull View itemView) {
        super(itemView);
        txtArtist = itemView.findViewById(R.id.artistID);
        txtTitle = itemView.findViewById(R.id.titleID);
        imageViewPicture = itemView.findViewById(R.id.item_imageID);
        imageViewMenu = itemView.findViewById(R.id.item_menu_ID);
    }
}

The XML code for MainActivity:

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context=".MainActivity">

    <FrameLayout
        android:id="@+id/frame_layout_id"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_above="@id/bottom_navigation_ID" />

    <com.google.android.material.bottomnavigation.BottomNavigationView
        android:id="@+id/bottom_navigation_ID"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_alignParentBottom="true"
        android:layout_gravity="bottom"
        app:menu="@menu/bottom_navigation_menu" />

</RelativeLayout>

The XML code for RecyclerView:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".BibliotecaFragment">

    <androidx.recyclerview.widget.RecyclerView
        android:id="@+id/BibliotecaFragmentRecyclerViewID"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:background="#3C3A3A"
        app:layoutManager="androidx.recyclerview.widget.LinearLayoutManager">

    </androidx.recyclerview.widget.RecyclerView>

</LinearLayout>

And the XML code for each item into the RecyclerView:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/audio_itemID"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_marginTop="5dp"
    android:background="@color/black"
    android:orientation="horizontal">

    <ImageView
        android:id="@+id/item_imageID"
        android:layout_width="60dp"
        android:layout_height="60dp"
        android:background="@drawable/ic_launcher_foreground"
        android:padding="5dp" />

    <TextView
        android:id="@+id/artistID"
        android:layout_width="wrap_content"
        android:layout_height="match_parent"
        android:layout_marginLeft="10dp"
        android:gravity="center"
        android:text="Artist"
        android:textColor="@color/white" />

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="match_parent"
        android:layout_marginLeft="10dp"
        android:gravity="center"
        android:text="-"
        android:textColor="@color/white" />

    <TextView
        android:id="@+id/titleID"
        android:layout_width="wrap_content"
        android:layout_height="match_parent"
        android:layout_marginLeft="10dp"
        android:gravity="center"
        android:text="Title"
        android:textColor="@color/white" />

    <ImageView
        android:id="@+id/item_menu_ID"
        android:layout_width="40dp"
        android:layout_height="40dp"
        android:layout_marginLeft="150dp"
        android:background="@drawable/ic_baseline_more_vert"
        android:padding="5dp"
        android:layout_gravity="center_vertical"/>

</LinearLayout>

Sorry for my english, I know it is not perfect, I hope you guys can help me with this.

Rubén.

Answer 1

I'm having the same problem and currently have no answer. You can try my method but only works if your recycler items are definite. Goto your viewholder class=>

@Override
public int getItemCount() {
    return num;
}

Where num is the number of your items in recyclerview.