CODEWITHSUNDEEP
androidfirebasefirebase-realtime-database
Luccas Freitas
Luccas Freitas

Reputation: 41

Get data from onDataChange

I need to return a data from Firebase to a Java Object, but even using an Interface, it always returns me null. Some help?

I created a "Coordinate" object inside the method and I'm trying to access the data like this: readData(value -> coordinates = value , offer);

public interface CoordinatesCallback {
    void onCallBack(Coordinates value);
}

public void readData(CoordinatesCallback callback, Offer offer) {
    String storeId = Integer.toString(offer.getStore().getId());

    mDatabase.child("stores").child(storeId).child("coordinates").addValueEventListener(new ValueEventListener() {
        @Override
        public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
            Coordinates coordinates = dataSnapshot.getValue(Coordinates.class);

            callback.onCallBack(coordinates);
        }

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

        }
    });
}

Upvotes: 0

Views: 253

Answers (1)

Doug Stevenson
Doug Stevenson

Reputation: 317467

That's not how getValue() works. You have to pass it the Class object of a Java POJO with getters and setters for each field of the database you want to read. From the linked Javadoc:

This method is used to marshall the data contained in this snapshot into a class of your choosing. The class must fit 2 simple constraints:

  1. The class must have a default constructor that takes no arguments
  2. The class must define public getters for the properties to be assigned. Properties without a public getter will be set to their default value when an instance is deserialized

Upvotes: 1

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