CODEWITHSUNDEEP
javaandroidfirebasefirebase-realtime-database
knightcube
knightcube

Reputation: 159

How can I Return a Child's Value in Firebase from a Method in Android?

I am trying to fetch the user details of a particular user using his UID. I need a method that can return the userName as a String type so that I can store it and display it in my app. 

getUserName("UID");

This is how my database looks like - enter image description here

This is what i tried doing - 

 private String getUserName(String startedBy) {
    mProfileRef=database.getReference("Profile").child(startedBy).child("UserDetails").child("userName");
    mProfileRef.addListenerForSingleValueEvent(new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {
            userName = dataSnapshot.getValue(String.class);
            Log.i(TAG, "onDataChange: "+userName);

        }

        @Override
        public void onCancelled(DatabaseError databaseError) {

        }
    });
    return userName;
}

The Log statement executes perfectly and gives the correct userName based on the UID. The method does not return the userName. It returns null. How do I return the userName?

Upvotes: 0

Views: 55

Answers (2)

Umar Hussain
Umar Hussain

Reputation: 3527

You can directly update your view inside the call back for firebase database read given your firebase code is also in the same class.

private void getUserName(String startedBy, TextView textView) {
    mProfileRef=database.getReference("Profile").child(startedBy).child("UserDetails").child("userName");
    mProfileRef.addListenerForSingleValueEvent(new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {
            userName = dataSnapshot.getValue(String.class);
            textView.setText(userName);
            Log.i(TAG, "onDataChange: "+userName);

        }

        @Override
        public void onCancelled(DatabaseError databaseError) {

        }
    });
}

The answer from Waqas Pervez is also a very good solution.

Upvotes: 0

M.Waqas Pervez
M.Waqas Pervez

Reputation: 2430

It is because Firebase operations are performed asynchronous. That means the method onDataChange executes on a background thread meanwhile your UI thread executes the original method and returns the value without waiting for the Firebase response.

The solution can be done with using an interface.

1 - Define an interface

public interface OnDataLoaded {

   onDataLoaded(String username);

}

2 - Pass the interface as the method argument

public void getUserName(String startedBy, OnDataLoaded onDataLoaded)

3 - Use the interface to pass the username.

mProfileRef = database.getReference("Profile").child(startedBy).child("UserDetails").child("userName");
mProfileRef.addListenerForSingleValueEvent(new ValueEventListener() {
    @Override
    public void onDataChange(DataSnapshot dataSnapshot) {
        userName = dataSnapshot.getValue(String.class);
        onDataLoaded.onDataLoaded(username);
        Log.i(TAG, "onDataChange: "+userName);

    }

    @Override
    public void onCancelled(DatabaseError databaseError) {

    }
});

4 - Use the interface in your Activity/Fragment.

public class yourActivity implements OnDataLoaded

5 - You control will be transfered to you activity method onDataLoaded

@Override
public void onDataLoaded(String userName) {
    // your userName will be available here.
    // you can use your bindings here.
}

NOTE : wrote with without any IDE. Might contain some syntax errors.

Upvotes: 3

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