How to retrieve data from merge tasks in firestore query?

Question

please can someone tell me how to retrieve all three tasks? Actually, I'm able to retrieve only two tasks.

CollectionReference players = db.collection("gamers");

    Task task1 = players.whereEqualTo("player_id_one", myId)
            .get();

    Task task2 = players.whereEqualTo("player_id_two", myId)
            .get();
Task task3 = players.whereEqualTo("player_id_three",myId).get();

    Task<List<QuerySnapshot>> allTasks = Tasks.whenAllSuccess(task1, task2,task3);
    allTasks.addOnSuccessListener(new OnSuccessListener<List<QuerySnapshot>>() {
        @Override
        public void onSuccess(List<QuerySnapshot> querySnapshots) {
            for (QuerySnapshot queryDocumentSnapshots : querySnapshots) {
                for (QueryDocumentSnapshot documentSnapshot : queryDocumentSnapshots) {
                    Modelgame players = documentSnapshot.toObject(Modelgame.class);
                    result.add(modelplayer);
                    adapter.notifyDataSetChanged();

                }
            }
        }
    });

you can give a try by adding `task4` and then you may get 3 instead of 4 — Vishal Beep, May 01 '22 at 08:00
Oh I see.. but i have no idea how I'm supposed to arrange the for loop so that it display the results. If you have any ideas please your welcome — freeday same, May 01 '22 at 08:04
Can you tell me what output or error you are getting in your case. and what output or error after adding `task4`. — Vishal Beep, May 01 '22 at 08:08
Actually no error occurred. My code retrieve only two tasks but when i add the third and the fourth task. Nothing display in my recyclerView . — freeday same, May 01 '22 at 08:39
thank you I saw the problem firestore asked me to add an index query in my console ‍♂️.. It finally works — freeday same, May 01 '22 at 14:25

score 1 · Answer 1 · answered May 01 '22 at 08:10

1

When you're using Tasks#whenAllSuccess(Task...<?> tasks) method it:

Returns a Task with a list of Task results that completes successfully when all of the specified Tasks complete successfully.

This means that the List you're getting is not a List<QuerySnapshot> but a List<Object>:

allTasks.addOnSuccessListener(new OnSuccessListener<List<Object>>() {
    @Override
    public void onSuccess(List<Object> querySnapshots) {
        //Loop through the list only once
        for (Object object : querySnapshots) {
            Modelgame players = ((DocumentSnapshot) object).toObject(Modelgame.class);
            result.add(modelplayer);
            Log.d("TAG", players.getName());
        }
        adapter.notifyDataSetChanged(); //Added when the for loop ends.
    }
});

So once all the tasks are successful you only need to loop through the results once and cast the object to a DocumentSnapshot object and call toObject().

answered May 01 '22 at 08:10

Alex Mamo

130,605
17
163
193

i just tried it . My recyclerView display nothing it remains blank – freeday same May 01 '22 at 08:50
Does this `Log.d("TAG", players.getName());` pint something in the logcat? If you don't have a getter for the name, then use another one. Besides that, please edit your question and add your database structure as a screenshot. Have you also tried to use a hard-coded value for `myId`? – Alex Mamo May 01 '22 at 09:21
I tried the code again but this time an error occurred. Java.lang.Class.CastException: com.google.firebase.firestore.QuerySnapshot cannot be cast to com.google.firebase.firestore.DocumentSnapshot – freeday same May 01 '22 at 13:50
thank you I saw the problem firestore asked me to add an index query in my console ‍♂️.. It finally works – freeday same May 01 '22 at 14:24
actually yes. Check internet connection.. check internet bandwidth – freeday same May 08 '22 at 13:16
actually yes. is there a firestore or firebase code to check the internet connection? – freeday same May 08 '22 at 13:24
For that, I recommend you check this [answer](https://stackoverflow.com/questions/52279144/how-to-verify-if-user-has-network-access-and-show-a-pop-up-alert-when-there-isn). So like the answer states, you can use `.isFromCache()`, right? – Alex Mamo May 09 '22 at 09:04
Can I help you with other information, other than that? – Alex Mamo May 09 '22 at 09:05

How to retrieve data from merge tasks in firestore query?

1 Answers1