Я делаю напоминание. Как реализовать таймер с уведомлением?

Question

Привет, ребята, это приложение-напоминание, в котором я могу добавить информацию и установить ее на главной странице и сохранить информацию в базе данных, но, тем не менее, я не уверен, как реализовать таймер, который пользователь может установить и получать уведомления, когда готово. Я могу отправить файл, если необходимо.

MainActivity

public class MainActivity2 extends AppCompatActivity {

    TextView titlepage, subtitlepage, endpage;
    Button btnAddNew;

    DatabaseReference reference;
    RecyclerView ourdoes;
    ArrayList<MyDoes> list;
    DoesAdapter doesAdapter;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main2);

        titlepage = findViewById(R.id.titlepage);
        subtitlepage = findViewById(R.id.subtitlepage);
        endpage = findViewById(R.id.endpage);

        btnAddNew = findViewById(R.id.btnAddNew);

        // import font

      // btnAddNew.setTypeface(MLight);

        btnAddNew.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent a = new Intent(MainActivity2.this,NewTaskAct.class);
                startActivity(a);
            }
        });


        // working with data
        ourdoes = findViewById(R.id.ourdoes);
        ourdoes.setLayoutManager(new LinearLayoutManager(this));
        list = new ArrayList<MyDoes>();

        // get data from firebase
        reference = FirebaseDatabase.getInstance().getReference().child("DoesApp");
        reference.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(DataSnapshot dataSnapshot) {
                // set code to retrive data and replace layout
                for(DataSnapshot dataSnapshot1: dataSnapshot.getChildren())
                {
                    MyDoes p = dataSnapshot1.getValue(MyDoes.class);
                    list.add(p);
                }
                doesAdapter = new DoesAdapter(MainActivity2.this, list);
                ourdoes.setAdapter(doesAdapter);
                doesAdapter.notifyDataSetChanged();
            }

            @Override
            public void onCancelled(DatabaseError databaseError) {
                // set code to show an error
                Toast.makeText(getApplicationContext(), "No Data", Toast.LENGTH_SHORT).show();
            }
        });

    }

NewTask Activity (если пользователь может добавить заголовок, описание напоминания, Я думаю, что таймер должен быть здесь)

public class NewTaskAct extends AppCompatActivity {

    TextView titlepage, addtitle, adddesc, adddate;
    EditText titledoes, descdoes, datedoes;
    Button btnSaveTask, btnCancel;
    DatabaseReference reference;
    Integer doesNum = new Random().nextInt();
    String keydoes = Integer.toString(doesNum);

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_new_task);

        titlepage = findViewById(R.id.titlepage);

        addtitle = findViewById(R.id.addtitle);
        adddesc = findViewById(R.id.adddesc);
        adddate = findViewById(R.id.adddate);

        titledoes = findViewById(R.id.titledoes);
        descdoes = findViewById(R.id.descdoes);
        datedoes = findViewById(R.id.datedoes);

        btnSaveTask = findViewById(R.id.btnSaveTask);
        btnCancel = findViewById(R.id.btnCancel);

        btnSaveTask.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                // insert data to database
                reference = FirebaseDatabase.getInstance().getReference().child("DoesApp").
                        child("Does" + doesNum);
                reference.addValueEventListener(new ValueEventListener() {
                    @Override
                    public void onDataChange(DataSnapshot dataSnapshot) {

                        dataSnapshot.getRef().child("titledoes").setValue(titledoes.getText().toString());
                        dataSnapshot.getRef().child("descdoes").setValue(descdoes.getText().toString());
                        dataSnapshot.getRef().child("datedoes").setValue(datedoes.getText().toString());
                        dataSnapshot.getRef().child("keydoes").setValue(keydoes);

                        Intent a = new Intent(NewTaskAct.this,MainActivity2.class);
                        startActivity(a);

                    }

                    @Override
                    public void onCancelled(DatabaseError databaseError) {

                    }
                });
            }
        });



    }
}

Адаптер Я думаю, что таймер должен быть вызван здесь, но опять же, я не уверен

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

    Context context;
    ArrayList<MyDoes> myDoes;

    public DoesAdapter(Context c, ArrayList<MyDoes> p) {
        context = c;
        myDoes = p;
    }


    @NonNull
    @Override
    public MyViewHolder onCreateViewHolder(@NonNull ViewGroup viewGroup, int i) {
        return new MyViewHolder(LayoutInflater.from(context).inflate(R.layout.item_does,viewGroup, false));
    }

    @Override
    public void onBindViewHolder(@NonNull final MyViewHolder myViewHolder, int i) {
        myViewHolder.titledoes.setText(myDoes.get(i).getTitledoes());
        myViewHolder.descdoes.setText(myDoes.get(i).getDescdoes());
        myViewHolder.datedoes.setText(myDoes.get(i).getDatedoes());

        final String getTitleDoes = myDoes.get(i).getTitledoes();
        final String getDescDoes = myDoes.get(i).getDescdoes();
        final String getDateDoes = myDoes.get(i).getDatedoes();
        final String getKeyDoes = myDoes.get(i).getKeydoes();

        myViewHolder.itemView.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent aa = new Intent(context,EditTaskAct.class);
                aa.putExtra("titledoes", getTitleDoes);
                aa.putExtra("descdoes", getDescDoes);
                aa.putExtra("datedoes", getDateDoes);
                aa.putExtra("keydoes", getKeyDoes);
                context.startActivity(aa);
            }
        });
    }

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

    class MyViewHolder extends RecyclerView.ViewHolder {

        TextView titledoes, descdoes, datedoes, keydoes;

        public MyViewHolder(@NonNull View itemView) {
            super(itemView);
            titledoes = (TextView) itemView.findViewById(R.id.titledoes);
            descdoes = (TextView) itemView.findViewById(R.id.descdoes);
            datedoes = (TextView) itemView.findViewById(R.id.datedoes);
        }
    }

}

MyDoes (Где геттеры и сеттеры есть)

public class MyDoes {

    String titledoes;
    String datedoes;
    String descdoes;
    String keydoes;

    public MyDoes() {
    }

    public MyDoes(String titledoes, String datedoes, String descdoes, String keydoes) {
        this.titledoes = titledoes;
        this.datedoes = datedoes;
        this.descdoes = descdoes;
        this.keydoes = keydoes;
    }

    public String getKeydoes() {
        return keydoes;
    }

    public void setKeydoes(String keydoes) {
        this.keydoes = keydoes;
    }

    public String getTitledoes() {
        return titledoes;
    }

    public void setTitledoes(String titledoes) {
        this.titledoes = titledoes;
    }

    public String getDatedoes() {
        return datedoes;
    }

    public void setDatedoes(String datedoes) {
        this.datedoes = datedoes;
    }

    public String getDescdoes() {
        return descdoes;
    }

    public void setDescdoes(String descdoes) {
        this.descdoes = descdoes;
    }
}