CODEWITHSUNDEEP
androidfirebasefirebase-realtime-database
Karim Alaa
Karim Alaa

Reputation: 344

retrieve multiple date from firebase using references

I have two classes Patient and Appointment

The structure of my database

I need to select all appointments in a specific date and for each one of the appointments the data of patient using patient id

Patient.java

public class Patient {
    private String name;
    private String phone;
    private String patient_id;

    public Patient(){

    }

    public Patient(String name, String phone, String patient_id) {
        this.name = name;
        this.phone = phone;
        this.patient_id = patient_id;
    }
}

Appointment.java

public class Appointment {
    @Exclude
    public static final int START_HOUR = 8;
    @Exclude
    public static final int START_MINUTE = 0;
    @Exclude
    public static final int MAX_NUMBER = 100;
    @Exclude
    public static final int FIXED_PERIOD = 15;
    @Exclude
    private Patient patient;
    @Exclude
    private String date;

    private String patient_id;
    private String time;
    private String color;


    public Appointment(){

    }

    public Appointment(String patient_id, String date, String time, String color) {
        this.patient_id = patient_id;
        this.date = date;
        this.time = time;
        this.color = color;
    }
}

Now I need to perform retrieving

I have tried the following code, but it failed as every task in the for loop is run in a different thread handled by firebase

 mDatabase.child("appointments").child(date).addListenerForSingleValueEvent(new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {
            appointmentsList = new ArrayList<>();
            //Toast.makeText(getActivity(),String.valueOf(dataSnapshot.getChildrenCount()),Toast.LENGTH_LONG).show();
            for(DataSnapshot d:dataSnapshot.getChildren()){
                String last_time = "";
                if(d.getValue().getClass().equals(String.class)){
                   last_time = d.getValue().toString();
                }else {
                    final Appointment appointment = d.getValue(Appointment.class);

                    mDatabase.child("patients").child(appointment.getPatient_id()).addListenerForSingleValueEvent(new ValueEventListener() {
                        @Override
                        public void onDataChange(DataSnapshot dataSnapshot2) {
                            Patient patient = dataSnapshot2.getValue(Patient.class);
                            appointment.setPatient(patient);
                            appointmentsList.add(appointment);
                        }

                        @Override
                        public void onCancelled(DatabaseError databaseError2) {

                        }
                    });


                }
            }
            mNoteView.setText(getString(R.string.data_for_date, date));
            updatePatientsAdapter();
        }

        @Override
        public void onCancelled(DatabaseError databaseError) {

        }
    });

How can I handle it, or can i promote the database structure to solve it ?

Upvotes: 2

Views: 271

Answers (1)

Levi Moreira
Levi Moreira

Reputation: 12005

You're trying to apply a relational structure to firebase database, which is a non relational database. You will need to restructure your data in order to perform queries more effectively. Checkout this article to help you denormalize your data.

Instead of saving the patient_id in each appointement you should save the patient itself.

Note that firebase has tools to perform updates in objects in multiple locations exatcly because you can have the same patient in multiple appointments.

You can still keep the patients "table", but you'll need to worry about keeping your data in sync when updating patients.

Upvotes: 1

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