Completion Handler Firebase in Android

Question

I try to get first all my data, before I return my values... But I can't find on the internet something about completion handler for the firebaseoperation.

Can somebody help?

My current implementation doesn't work well....

public List<ExampleClass> GetAllExamples() {
  Query examplequery = db.child("example");
  exampleList = new ArrayList<ExampleClass>();

  examplequery.addChildEventListener(new ChildEventListener() {

    @Override
    public void onChildAdded(DataSnapshot dataSnapshot, String s) {
      String value = getValue(dataSnapshot.getValue().toString());
      String key = dataSnapshot.getKey();
      ExampleClass ex = new Country(key, value);
      exampleList.add(ex);
    }

    @Override
    public void onChildChanged(DataSnapshot dataSnapshot, String s) {

    }

    @Override
    public void onChildRemoved(DataSnapshot dataSnapshot) {

    }

    @Override
    public void onChildMoved(DataSnapshot dataSnapshot, String s) {

    }

    @Override
    public void onCancelled(FirebaseError firebaseError) {

    }
  });

  return exampleList;
}

Firebase synchronizes data at a location, so the query is never really done. If you're looking to detect when the initial data has been synchronized, see http://stackoverflow.com/questions/18270995/how-to-retreive-only-new-data — Frank van Puffelen, Jul 09 '16 at 23:37

score 1 · Answer 1 · answered Jul 10 '16 at 07:00

With the help of Frank I found a proper solution

examplequery.addListenerForSingleValueEvent(new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {
            // do something after data is synchronized
        }

        @Override
        public void onCancelled(FirebaseError firebaseError) {

        }
    });

Completion Handler Firebase in Android

1 Answers1