RecyclerView items, with data from multiple arrayList, are been repeated when the fragment it is restarted

Question

I have recyclerView in a fragment that is populated by data from three different arrayLists. Even if i clear the three arrayLists before running the method that adds data to them, items of the recyclerView will be repeated whem this fragment is opens again. How can I solve it?

My fragment:

public class execFragment extends Fragment {
    private RecyclerView recyclerView;
    private String nomeAluno, teste="", exec="", jaaj, disc;
    private DatabaseReference reference = FirebaseDatabase.getInstance().getReference("usuarios/");
    private DatabaseReference referenceExec = FirebaseDatabase.getInstance().getReference("salas/");
    private ArrayList<String> listaExercicio;
    private TextView txtPendente;
    private ArrayList<String> listaSalas;
    private ArrayList<String> listData;
    private ArrayList<String> listaDisc;
    private EditText edtPesquisa;
    private Date currentTime;
    private int count= 0;
    private adapterExec adapterExec;
    private ArrayList<String> nomeSalas = new ArrayList<String>();

    private DatabaseReference referencePegarExec, referencePegarDisc;

    public execFragment() {
        // Required empty public constructor
    }


    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        View view= inflater.inflate(R.layout.fragment_exec, container, false);

        recyclerView= view.findViewById(R.id.recyclerView);
        edtPesquisa= view.findViewById(R.id.edtPesquisa);
        txtPendente= view.findViewById(R.id.txtPendente);
        final Context context = view.getContext();
        listaExercicio= new ArrayList<>();
        listaSalas= new ArrayList<>();
        listData= new ArrayList<>();
        listaDisc= new ArrayList<>();

        // edtPesquisa.requestFocus();
        // configurar adpater
        adapterExec= new adapterExec(listaExercicio, listaDisc, listData,context);
        //  adapterSalas adapterExec= new adapterSalas(listaExercicio, context);
        //configurar recycler view
        RecyclerView.LayoutManager layoutManager = new LinearLayoutManager(context);
        recyclerView.setLayoutManager(layoutManager);
        // recyclerView.setHasFixedSize(true);
        recyclerView.addItemDecoration(new DividerItemDecoration(context, LinearLayout.VERTICAL));
        recyclerView.setAdapter( adapterExec );

        //evento click
        recyclerView.addOnItemTouchListener(
                new RecyclerItemClickListener(context, recyclerView, new RecyclerItemClickListener.OnItemClickListener() {
                    @Override
                    public void onItemClick(View view, int position) {

                        // Toast.makeText(context, "Item selecionado: " + exercicio.getNomeAtv(),Toast.LENGTH_SHORT).show();
                        Intent intent = new Intent(getActivity(), resolverExecActivity.class);
                        intent.putExtra("nomeSala", listaSalas.get(position));
                        intent.putExtra("nomeExec", listaExercicio.get(position));
                        startActivity(intent);
                    }

                    @Override
                    public void onLongItemClick(View view, int position) {

                        //  Toast.makeText(context, "Click longo: "  + exercicio.getNomeAtv(),Toast.LENGTH_SHORT).show();
                        Intent intent = new Intent(getActivity(), resolverExecActivity.class);
                        startActivity(intent);
                    }

                    @Override
                    public void onItemClick(AdapterView<?> parent, View view, int position, long id) {

                    }
                })
        );

        return view;

    }

    @Override
    public void onStart() {
        super.onStart();
        listaExercicio.clear();
        listaSalas.clear();
        listData.clear();
        listaDisc.clear();
        pegarExec();
    }


    public void pegarExec(){

        FirebaseAuth autenticacao = FirebaseAuth.getInstance();
        String emailUsu = autenticacao.getCurrentUser().getEmail();
        reference.orderByChild("email").equalTo(emailUsu).addListenerForSingleValueEvent(new ValueEventListener() {
            @Override
            public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                for (DataSnapshot datas : dataSnapshot.getChildren()) {
                    nomeAluno = datas.child("nome").getValue().toString();
                    referenceExec.orderByChild("alunos/"+ nomeAluno+"/codigo").equalTo(nomeAluno).addListenerForSingleValueEvent(new ValueEventListener() {
                        @Override
                        public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                            if(dataSnapshot.exists()){

                                for (DataSnapshot datas : dataSnapshot.getChildren()) {
                                    teste= datas.getKey();
                                    nomeSalas.add(teste);

                                }
                                for(int i = 0; i < nomeSalas.size();i++ ) {
                                    referencePegarExec = FirebaseDatabase.getInstance().getReference("salas/" + nomeSalas.get(i) );
                                    final int finalI = i;

                                    referencePegarExec.child("exercicios").addValueEventListener(new ValueEventListener() {
                                        @Override
                                        public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                                            for (DataSnapshot dsp : dataSnapshot.getChildren()) {
                                                jaaj = dsp.getKey();
                                                if (!jaaj.equals("1")) {

                                                    SimpleDateFormat sdf = new SimpleDateFormat("dd/MM/yyyy");
                                                    Date strDate = null;
                                                    try {
                                                        strDate = sdf.parse(dataSnapshot.child(jaaj + "/dataValidade").getValue(String.class));
                                                    } catch (ParseException e) {
                                                        e.printStackTrace();
                                                    }
                                                    if (System.currentTimeMillis() < strDate.getTime()) {

                                                        listaSalas.add(nomeSalas.get(finalI));
                                                        listData.add(dataSnapshot.child(jaaj + "/dataValidade").getValue(String.class));
                                                        listaExercicio.add(jaaj);

                                                        referencePegarDisc = FirebaseDatabase.getInstance().getReference("salas/" + nomeSalas.get(finalI) );
                                                        referencePegarDisc.child("disciplina").addValueEventListener(new ValueEventListener() {
                                                            @Override
                                                            public void onDataChange(@NonNull DataSnapshot snap) {
                                                                disc= snap.getValue(String.class);
                                                                listaDisc.add(disc);
                                                                adapterExec.notifyDataSetChanged();
                                                            }

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

                                                            }
                                                        });
                                                    }
                                                }
                                            }



                                        }

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

                                        }
                                    });
                                }//adapterExec.notifyDataSetChanged();

                            }else{
                                txtPendente.setText("Nenhum exercício pendente");
                            }
                        }

                        @Override
                        public void onCancelled(@NonNull DatabaseError databaseError) {
                            throw databaseError.toException();
                        }
                    });

                }
            }

            @Override
            public void onCancelled(@NonNull DatabaseError databaseError) {
                throw databaseError.toException();
            }
        }); 
    }
}

My adapter:

public class adapterExec extends RecyclerView.Adapter<adapterExec.MyViewHolder> {

    private ArrayList<String> listaExercicio;
    private ArrayList<String> listaDic;
    private ArrayList<String> listaData;
    private Context context;


    public adapterExec(ArrayList<String> listaExercicio, ArrayList<String> listaDic, ArrayList<String> listaData, Context context) {
        this.listaExercicio = listaExercicio;
        this.listaDic = listaDic;
        this.listaData = listaData;
        this.context = context;
    }

    @NonNull
    @Override
    public MyViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int i) {
        View itemLista = LayoutInflater.from(parent.getContext())
                .inflate(R.layout.adapterexec_lista, parent, false);

        return new MyViewHolder(itemLista);
    }

    @Override
    public void onBindViewHolder(@NonNull MyViewHolder holder, int position) {

        holder.nomeAtv.setText(listaExercicio.get(position));
        holder.dataVenc.setText(listaData.get(position));
        holder.materia.setText(listaDic.get(position));

    }

    @Override
    public int getItemCount() {
        return listaExercicio.size();
    }
    @Override
    public long getItemId(int position) {
        return position;
    }

    @Override
    public int getItemViewType(int position) {
        return position;
    }

    public class MyViewHolder extends RecyclerView.ViewHolder{
        TextView nomeAtv;
        TextView dataVenc;
        TextView materia;
        public MyViewHolder(@NonNull View itemView) {
            super(itemView);

            nomeAtv= itemView.findViewById(R.id.textNomeAtv);
            dataVenc=itemView.findViewById(R.id.textDataVenc);
            materia= itemView.findViewById(R.id.textMateria);
        }
    }

}

Answer 1

Try shifting your code to clear things to be in the onResume .

If that doesn't work, evaluate at what point you are calling your public pegarExec() function, because that may be being called more than once.

See: The lifecycle diagram @ https://developer.android.com/guide/components/fragments

Answer 2

This is irrelevant to the question but try to do your work in onViewCreated instead of onCreateView as you will get more crashes in onCreateView trying to work with context.

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                     Bundle savedInstanceState) {
    super.onCreateView(inflater, container, savedInstanceState);
    // Inflate the layout for this fragment
    View view= inflater.inflate(R.layout.fragment_exec, container, false);
    return view;
}


@Override
public void onViewCreated(View view, Bundle onSaveInstanceState) {
     super.onViewCreated(view, onSaveInstanceState);
     recyclerView= view.findViewById(R.id.recyclerView);
     edtPesquisa= view.findViewById(R.id.edtPesquisa);
     txtPendente= view.findViewById(R.id.txtPendente);
     final Context context = view.getContext();
     listaExercicio= new ArrayList<>();
     listaSalas= new ArrayList<>();
     listData= new ArrayList<>();
     listaDisc= new ArrayList<>();
    // edtPesquisa.requestFocus();
     // configurar adpater
     adapterExec= new adapterExec(listaExercicio, listaDisc, listData,context);
   //  adapterSalas adapterExec= new adapterSalas(listaExercicio, context);
     //configurar recycler view
     RecyclerView.LayoutManager layoutManager = new LinearLayoutManager(context);
     recyclerView.setLayoutManager(layoutManager);
    // recyclerView.setHasFixedSize(true);
     recyclerView.addItemDecoration(new DividerItemDecoration(context, LinearLayout.VERTICAL));
     recyclerView.setAdapter( adapterExec );

     //evento click
     recyclerView.addOnItemTouchListener(
       new RecyclerItemClickListener(context, recyclerView, new RecyclerItemClickListener.OnItemClickListener() {
           @Override
           public void onItemClick(View view, int position) {

              // Toast.makeText(context, "Item selecionado: " + exercicio.getNomeAtv(),Toast.LENGTH_SHORT).show();
               Intent intent = new Intent(getActivity(), resolverExecActivity.class);
               intent.putExtra("nomeSala", listaSalas.get(position));
               intent.putExtra("nomeExec", listaExercicio.get(position));
               startActivity(intent);
           }

           @Override
           public void onLongItemClick(View view, int position) {

             //  Toast.makeText(context, "Click longo: "  + exercicio.getNomeAtv(),Toast.LENGTH_SHORT).show();
               Intent intent = new Intent(getActivity(), resolverExecActivity.class);
               startActivity(intent);
           }

           @Override
           public void onItemClick(AdapterView<?> parent, View view, int position, long id) {

           }
       })
);


}

My Guess as to what's happening is that your data is changing/shifting as you pull the values and that's causing the items to be added multiple times.