How to connect firebase firestore to realtime database?

Question

I made an application that users can earn points by taking quizzes. I have a leader board too.

my primary database is cloud firestore. but I need the leaderboard to be more real-time like it needs to update every time when a user earns points without refreshing or closing the fragment.

So I need to connect firebase firestore to real-time databases, (if I change the firestore data(like coins for the specified user or any), it needs to change the real-time data too)

I made codes but it didn't work well. I have attached the code here.

 private void LoadFirestore() {
    firebaseFirestore.collection("Users")
            .document(FirebaseAuth.getInstance().getUid())
            .get().addOnSuccessListener(new OnSuccessListener<DocumentSnapshot>() {
        @Override
        public void onSuccess(DocumentSnapshot documentSnapshot) {

            user = documentSnapshot.toObject(User.class); 
            totalCoins.setText(String.valueOf(user.getCoins()));

        }
    });
}


private void uploadToRealtime() {

    HashMap<String, Object> map = new HashMap<>();
    map.put("coins", totalCoins);
    firebaseDatabase.getReference().child("Users").child(FirebaseAuth.getInstance().getUid())

            .updateChildren(map);


            }
}

Firestore supports [realtime listeners too](https://firebase.google.com/docs/firestore/query-data/listen), so did you consider https://stackoverflow.com/questions/46720997/leaderboard-ranking-with-firebase? — Frank van Puffelen, Jun 23 '21 at 18:23
@FrankvanPuffelen but if I added some bonus point to a specified user in firestore, it won't appear in the real-time database. — Angel, Jun 23 '21 at 18:30
@AlexMamo because real-time DB will get the data more real-time, its too hard to find some datas. — Angel, Jun 24 '21 at 11:59
@AlexMamo because real-time DB will get the data more real-time, it's too hard to find some data. and firestore is more acceptable for finding specific data, can add to deferent categories, collection, document, fields. but it is not real time. — Angel, Jun 24 '21 at 11:59
The Realtime Database doesn't get the data more real-time than Cloud Firestore. You can confidently use Cloud Firestore ;) — Alex Mamo, Jun 24 '21 at 12:00
@AlexMamo is it ?. but when a user earn points it will not add to the points screen until they refreshed or closed and reopen the fragment — Angel, Jun 24 '21 at 12:02
Yes, it does. As FrankvanPuffelen already mentioned in his comment, use [real-time listeners](https://firebase.google.com/docs/firestore/query-data/listen). — Alex Mamo, Jun 24 '21 at 14:17

score 1 · Accepted Answer · answered Jun 23 '21 at 20:03

You can use a onSnapshotListener to get the fata directly from firestore in realtime. Here is a basic example for that:

final DocumentReference docRef = db.collection("cities").document("SF");
docRef.addSnapshotListener(new EventListener<DocumentSnapshot>() {
    @Override
    public void onEvent(@Nullable DocumentSnapshot snapshot,
                        @Nullable FirebaseFirestoreException e) {
        if (e != null) {
            Log.w(TAG, "Listen failed.", e);
            return;
        }

        if (snapshot != null && snapshot.exists()) {
            Log.d(TAG, "Current data: " + snapshot.getData());
        } else {
            Log.d(TAG, "Current data: null");
        }
    }
});

You can check more about it here.

Creating a sync to the RealtimeDatabase just for the realtime feature wouldn't make any sense here and would give you more costs in your Firebase project.

How to connect firebase firestore to realtime database?

1 Answers1