Retrieve data from nested saved data in Firebase

Question

I have this structure:

And I need to get the data from "OnlineClients". My attempt:

currentDriverId = mFireBaseAuth.getCurrentUser().getUid();
mDataBase = FirebaseDatabase.getInstance().getReference().child("Users").child("Driver").child(currentDriverId).child("OnlineClients");
final ArrayList<Student> users = new ArrayList<>();
        ValueEventListener postListener = new ValueEventListener() {
            @Override
            public void onDataChange(DataSnapshot dataSnapshot) {
                for (DataSnapshot data : dataSnapshot.getChildren()) {
                    Student student  = data.getValue(Student.class);
                    users.add(student);
                }

            }

            @Override
            public void onCancelled(DatabaseError databaseError) {
                // Getting Post failed, log a message
            }
        };
        mDataBase.addListenerForSingleValueEvent(postListener);

with error:

com.google.firebase.database.DatabaseException: Failed to convert value of type java.lang.Long to String

Student.Class:

public class Student {
    private String FirstName;
    private String LastName;
    private String StudentSchool;
    private String StudentState;
    private String StudentStreet;
    private String StudentStreetNumber;


    public Student(){
    }

    public String getFirstName() {
        return FirstName;
    }

    public void setFirstName(String firstName) {
        FirstName = firstName;
    }

    public String getLastName() {
        return LastName;
    }

    public void setLastName(String lastName) {
        LastName = lastName;
    }

    public String getStudentSchool() {
        return StudentSchool;
    }

    public void setStudentSchool(String studentSchool) {
        StudentSchool = studentSchool;
    }

    public String getStudentState() {
        return StudentState;
    }

    public void setStudentState(String studentState) {
        StudentState = studentState;
    }

    public String getStudentStreet() {
        return StudentStreet;
    }

    public void setStudentStreet(String studentStreet) {
        StudentStreet = studentStreet;
    }

    public String getStudentStreetNumber() {
        return StudentStreetNumber;
    }

    public void setStudentStreetNumber(String studentStreetNumber) {
        StudentStreetNumber = studentStreetNumber;
    }
}

Already tried: how to retrieve all the data within nested firebase database and similar without success.

Note: I only need to retrieve "OnlineClients" from current logged user (that's why I'm just using currentDriverId).

Please add the content of your `Student` class. – Alex Mamo Jul 15 '19 at 08:24 — Alex Mamo, Jul 15 '19 at 08:24

score 1 · Answer 1 · answered Jul 15 '19 at 08:22

Change this:

@Override
public void onDataChange(DataSnapshot dataSnapshot) {
  for (DataSnapshot data : dataSnapshot.getChildren()) {
      Student student  = data.getValue(Student.class);
      users.add(student);
   }

}

into this:

@Override
public void onDataChange(DataSnapshot dataSnapshot) {
  Student student  = dataSnapshot.getValue(Student.class);
  users.add(student);
}

Remove the for loop because when you are looping, you are retrieving the values as String. Also make sure when you use setValue() you are adding an object of Type Student as an argument.

Another way to retrieve the values is to do the following:

@Override
public void onDataChange(DataSnapshot dataSnapshot) {
 for (DataSnapshot data : dataSnapshot.getChildren()) {
    String firstName = data.child("FirstName").getValue(String.class);
    String lastName  = data.child("LastName").getValue(String.class);
     }
}

score 0 · Accepted Answer · answered Jul 15 '19 at 08:34

0

The problem in your code lies in the fact that your StudentStreetNumber field is declared in your Student class of type String while in your database is a number (long). To solve this, simply change the type of your property to long:

private long StudentStreetNumber;

Another problem in your code are the getters. To solve this problem too, please see my answer from the following post:

Firebase Android ListView not being displayed

answered Jul 15 '19 at 08:34

Alex Mamo

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That was it! Actually I had inconsistencies (in one class it was declared as int and probably then casted to long and in the other as String). It was not necessary to change my current code, but to fix these inconsistencies. – Miguel Duran Diaz Jul 15 '19 at 16:38

Retrieve data from nested saved data in Firebase

2 Answers2