How to know that Snapshot Listener is finished | firestore?

Question

I have this code that fetch data from specific sub-collection:

 db.collection("groups").document(id.get(i)).collection("members")
                .get()
                .addOnCompleteListener(new OnCompleteListener<QuerySnapshot>() {
                    @Override
                    public void onComplete(@NonNull Task<QuerySnapshot> task) {
                        if (task.isSuccessful()) {
                            for (QueryDocumentSnapshot document : task.getResult()) {
                                id.add(document.getId());
                                Log.e(Tag, document.getId() + " => " + document.getData());

                                if (task.getResult().isEmpty()) {
                                    Log.d(Tag, "onSuccess: LIST EMPTY");
                                    return;
                                } else {
                                    // Convert the whole Query Snapshot to a list
                                    // of objects directly! No need to fetch each
                                    // document.
                                    Log.e(Tag, task.getResult() + "");
                                    typeAll = task.getResult().toObjects(GroupMembers.class);
                                }
                            }
                        } else {
                            Log.e(Tag, "Error getting documents: ", task.getException());
                        }

But I need to call a method after fetching all the data by snapshots. How to achieve that? what should I test?

score 4 · Answer 1 · answered May 02 '18 at 10:58

4

How to know that Snapshot Listener is finished?

The Snapshot Listener is always listening for changes, unless you are removing it.

If you are looking to know when the data is completed loading from the database, note that you cannot know when all the members are completed downloaded becase Cloud Fireatore is a realtime database and getting data might never complete. That's why is named a realtime database because in any momemnt the data under the members collection can be changed, properties can be added or deleted.

You can use a CompletionListener only when you write or update data and you'll be notified when the operation has been acknowledged by Firebase servers but you cannot use this interface when reading data.

answered May 02 '18 at 10:58

Alex Mamo

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thanks a lot, good explaining. what I need is recalled my adapter after fetching new data, I used a handler to wait for 5 secondes but that is not the right way to do it – Reeman Adel May 02 '18 at 20:58
It seems that this is another question but in my opinion you should call `notifyDataSetChanged()` method in order to refresh the adapter or to create a new instance if needed. – Alex Mamo May 03 '18 at 09:31
1

Do you think that my answer helped you? – Alex Mamo May 03 '18 at 09:31
Ok, give it a try and keep me posted. – Alex Mamo May 04 '18 at 08:07

score 0 · Answer 2 · answered Jan 31 '19 at 21:57

Call your method to process the object list after you retrieve it:

                           if (task.isSuccessful()) {
                                for (QueryDocumentSnapshot document : task.getResult()) {
                                    id.add(document.getId());
                                    Log.e(Tag, document.getId() + " => " + document.getData());

                                    if (task.getResult().isEmpty()) {
                                        Log.d(Tag, "onSuccess: LIST EMPTY");
                                        return;
                                    } else {
                                        // Convert the whole Query Snapshot to a list
                                        // of objects directly! No need to fetch each
                                        // document.
                                        Log.e(Tag, task.getResult() + "");
                                        typeAll = task.getResult().toObjects(GroupMembers.class);

                                        // do something with typeall here

                                    }
                                }
                            } else {
                                Log.e(Tag, "Error getting documents: ", task.getException());
                            }

How to know that Snapshot Listener is finished | firestore?

2 Answers2