Firebase android pagination

Question

I\'m building an app which will show videos stored on firebase. The list of videos needs to be paginated fetching most recent 20 videos at a time.

Here is

Answer 1

If you want to get list from firebase realtime database descending with pagination you need use smth like this:

Query query = myRef.child("stories").orderByChild("takenAt").endAt(1600957136000L).limitToLast(30);

Full code, two requests

        List storyList = new ArrayList<>();
        
        FirebaseDatabase database = FirebaseDatabase.getInstance();
        DatabaseReference myRef = database.getReference();
        
        //first request will be look like this
        Query query = myRef.child("stories").orderByChild("takenAt").endAt(1600957136000L).limitToLast(30);
        query.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                if (dataSnapshot.exists()) {
                    for (DataSnapshot snapshot : dataSnapshot.getChildren()) {
                        Story story = snapshot.getValue(Story.class);
                        storyList.add(story);
                    }
                }
                Collections.reverse(storyList);
            }
            @Override
            public void onCancelled(@NonNull DatabaseError error) {
                Log.e("ptg", "onCancelled: ", error.toException());
            }
        });
        
        //second request
        long lastTakenAtInTheStoryList = storyList.get(storyList.size()-1).getTakenAt();
        Query query2 = myRef.child("stories").orderByChild("takenAt").endAt(lastTakenAtInTheStoryList).limitToLast(30);
        query2.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                if (dataSnapshot.exists()) {
                    for (DataSnapshot snapshot : dataSnapshot.getChildren()) {
                        Story story = snapshot.getValue(Story.class);
                        storyList.add(story);
                    }
                }
                Collections.reverse(storyList);
            }
            @Override
            public void onCancelled(@NonNull DatabaseError error) {
                Log.e("ptg", "onCancelled: ", error.toException());
            }
        });