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

Below is the code I'm using for pagination which shows the latest node first.

      public void getImages() {
            Query imagesQuery = FirebaseDatabase.getInstance().getReference().child("englishDps").child(mChildName).orderByKey().limitToLast(21);

            ChildEventListener childEventListener = new ChildEventListener() {
                @Override
                public void onChildAdded(DataSnapshot dataSnapshot, String s) {
                    Image image = dataSnapshot.getValue(Image.class);
                    image.setNodeKey(dataSnapshot.getKey());

                    mTempImages.add(image);
                    if (mTempImages.size() == 21) {
                        mLastKey = mTempImages.get(0).getNodeKey();
                        Collections.reverse(mTempImages);
                        mTempImages.remove(mTempImages.size() - 1);
                        mImages.addAll(mTempImages);
                        setAdapter();
                    }
                }

                @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(DatabaseError databaseError) {
                    if (isAdded()) {
                        Toast.makeText(getActivity(), "Problem loading more images...", Toast.LENGTH_LONG).show();
                    }
                }
            };

            imagesQuery.addChildEventListener(childEventListener);
        }


  @Override
    public void getMoreImages() {
        if (!mGettingMoreImages) {
            mGettingMoreImages = true;
            Query imagesQuery = FirebaseDatabase.getInstance().getReference("englishDps").child(mChildName).orderByKey().endAt(mLastKey).limitToLast(21);

            ChildEventListener childEventListener = new ChildEventListener() {
                @Override
                public void onChildAdded(DataSnapshot dataSnapshot, String s) {
                    Image image = dataSnapshot.getValue(Image.class);
                    image.setNodeKey(dataSnapshot.getKey());
                    mMoreImages.add(image);
                    if (mMoreImages.size() == 21) {
                        mLastKey = mMoreImages.get(0).getNodeKey();
                        Collections.reverse(mMoreImages);
                        mMoreImages.remove(mMoreImages.size() - 1);
                        mImages.addAll(mMoreImages);
                        mMoreImages.clear();
                        mGettingMoreImages = false;
                        mImagesAdapter.notifyDataSetChanged();
                        return;
                    }

                    if (mLastKey.equalsIgnoreCase(image.getNodeKey())) {
                        Collections.reverse(mMoreImages);
                        mImages.addAll(mMoreImages);
                        mMoreImages.clear();
                        mGettingMoreImages = false;
                        mImagesAdapter.onNoMoreImages();
                        ;
                        mImagesAdapter.notifyDataSetChanged();
                    }
                }

                @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(DatabaseError databaseError) {
                    if (isAdded()) {
                        Toast.makeText(getActivity(), "Problem loading more images...", Toast.LENGTH_LONG).show();
                    }
                }
            };

            imagesQuery.addChildEventListener(childEventListener);
        }
    }

Answer 2

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<Story> 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());
            }
        });

Answer 3

I have following method to paginate through a firebase realtime database node:

private void getUsers(String nodeId) {
        Query query;

        if (nodeId == null)
            query = FirebaseDatabase.getInstance().getReference()
                    .child(Consts.FIREBASE_DATABASE_LOCATION_USERS)
                    .orderByKey()
                    .limitToFirst(mPostsPerPage);
        else
            query = FirebaseDatabase.getInstance().getReference()
                    .child(Consts.FIREBASE_DATABASE_LOCATION_USERS)
                    .orderByKey()
                    .startAt(nodeId)
                    .limitToFirst(mPostsPerPage);

        query.addListenerForSingleValueEvent(new ValueEventListener() {
            @Override
            public void onDataChange(DataSnapshot dataSnapshot) {
                UserModel user;
                List<UserModel> userModels = new ArrayList<>();
                for (DataSnapshot userSnapshot : dataSnapshot.getChildren()) {
                    userModels.add(userSnapshot.getValue(UserModel.class));
                }

                mAdapter.addAll(userModels);
                mIsLoading = false;
            }

            @Override
            public void onCancelled(DatabaseError databaseError) {
                mIsLoading = false;
            }
        });
    }

Every time I reach the bottom of the paginated data, I call the getUsers(mAdapter.getLastItemId()); and then it brings the next set of records.

I have written a complete guide with open source sample app on this that you can check at https://blog.shajeelafzal.com/2017/12/13/firebase-realtime-database-pagination-guide-using-recyclerview/

Answer 4

accepted answear dos not work when less then the max. itmes (21) in database. this is my solution build on the accepted answer:

0)set variables

        private String lastMessageKey;
    private int totalItemCount;
    private int lastVisibleItem;
    private boolean isLoadingMoreFollowers = false;
    private boolean hasMoreItems = true;
    private boolean hasShownNoMoreItemsToast = false;
    private boolean initialLoad = true;
    private final int MAX_LOAD_ITEMS = 11;
    private final int VISIBLE_TRESHOLD = 1;

1) set a listener:

       private void setMessageListener() {

        if (childEventListener == null) {

            mmessageArrayList.clear();
            final ArrayList<Mmessage> tempMmessages = new ArrayList<>();
            query = mDatabaseInstace.getReference().child(chat1).child(F.CHATS).child(F.MESSAGES).orderByKey().limitToLast(MAX_LOAD_ITEMS-1);
            childEventListener = new ChildEventListener() {
                @Override
                public void onChildAdded(@NonNull DataSnapshot dataSnapshot, @Nullable String s) {
                    Log.d(TAG, "onChildAdded: -----------------> " + dataSnapshot);
                    Log.d(TAG, "onChildAdded: -----------------> " + s);

                    tempMmessages.add(dataSnapshot.getValue(Mmessage.class));
                    preloadMessagePics(tempMmessages);
                    if (initialLoad) {
                        lastMessageKey = tempMmessages.get(0).getMessagePushKey();
                        initialLoad = false;
                    }
                    mmessageArrayList.add(tempMmessages.size()-1, tempMmessages.get(0));
                    messageAdapter.notifyDataSetChanged();
                    tempMmessages.clear();


                }

                @Override
                public void onChildChanged(@NonNull DataSnapshot dataSnapshot, @Nullable String s) {
                    Log.d(TAG, "onChildChanged: --------------------------------->");

                }

                @Override
                public void onChildRemoved(@NonNull DataSnapshot dataSnapshot) {
                    Log.d(TAG, "onChildRemoved: ---------------------------------->");

                }

                @Override
                public void onChildMoved(@NonNull DataSnapshot dataSnapshot, @Nullable String s) {
                    Log.d(TAG, "onChildMoved: ------------------------------------>");

                }

                @Override
                public void onCancelled(@NonNull DatabaseError databaseError) {
                    Log.d(TAG, "onCancelled: ------------------------------------->");

                }
            };
            query.addChildEventListener(childEventListener);
        }

    }

2) set load more listener:

        private void setLoadMoreListener(){
        setup.RV_messages.addOnScrollListener(new RecyclerView.OnScrollListener() {
            @Override
            public void onScrolled(@NonNull RecyclerView recyclerView, int dx, int dy) {
                super.onScrolled(recyclerView, dx, dy);


                totalItemCount = linearLayoutManager.getItemCount();
                lastVisibleItem = linearLayoutManager.findLastVisibleItemPosition();



                if (!isLoadingMoreFollowers && totalItemCount <= (lastVisibleItem+VISIBLE_TRESHOLD) && (totalItemCount >= MAX_LOAD_ITEMS-1)){

                    if (hasMoreItems) {

                        getMoreMessages();
                        Toast.makeText(homeActivity, "load more items", Toast.LENGTH_SHORT).show();

                    }else {
                        if (!hasShownNoMoreItemsToast) {
                            Toast.makeText(homeActivity, "has no more items", Toast.LENGTH_SHORT).show();
                            hasShownNoMoreItemsToast = true;
                        }
                    }

                }

            }
        });
    }

3) get more items:

       private void getMoreMessages(){

        final ArrayList<Mmessage> tempMmessages = new ArrayList<>();

        isLoadingMoreFollowers = true;
        loadMoreQuery = mDatabaseInstace.getReference().child(chat1).child(F.CHATS).child(F.MESSAGES).orderByKey().endAt(lastMessageKey).limitToLast(MAX_LOAD_ITEMS);
        loadMoreChildEventListener = new ChildEventListener() {
            @Override
            public void onChildAdded(@NonNull DataSnapshot dataSnapshot, @Nullable String s) {

                tempMmessages.add(dataSnapshot.getValue(Mmessage.class));
                preloadMessagePics(tempMmessages);

                if (tempMmessages.size() == MAX_LOAD_ITEMS){

                    lastMessageKey = tempMmessages.get(0).getMessagePushKey();
                    Collections.reverse(tempMmessages);
                    tempMmessages.remove(0);
                    mmessageArrayList.addAll(tempMmessages);
                    isLoadingMoreFollowers = false;
                    messageAdapter.notifyDataSetChanged();
                    tempMmessages.clear();
                    return;
                }


                if (lastMessageKey.equalsIgnoreCase(tempMmessages.get(tempMmessages.size()-1).getMessagePushKey())){

                    Collections.reverse(tempMmessages);
                    tempMmessages.remove(0);
                    mmessageArrayList.addAll(tempMmessages);
                    isLoadingMoreFollowers = false;
                    hasMoreItems = false;
                    messageAdapter.notifyDataSetChanged();
                    tempMmessages.clear();

                }

            }

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

            }

            @Override
            public void onChildRemoved(@NonNull DataSnapshot dataSnapshot) {

            }

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

            }

            @Override
            public void onCancelled(@NonNull DatabaseError databaseError) {

            }
        };
        loadMoreQuery.addChildEventListener(loadMoreChildEventListener);

    }

have fun!!

Answer 5

In the past (but no longer) a question regarding implementing Pagination to a query on Firestore was marked as a duplicate of this question I will answer for FireStore here.

Paginate a query on android Firestore

Query query = db.collection("cities")
        .orderBy("population")
        .limit(25);

Query next = query;

 private void loadCities() {

     query = next;
     query.get()
        .addOnSuccessListener(new OnSuccessListener<QuerySnapshot>() {
            @Override
            public void onSuccess(QuerySnapshot documentSnapshots) {

                // Get the last visible document
                DocumentSnapshot lastVisible = 
                documentSnapshots.getDocuments()
                        .get(documentSnapshots.size() -1);

                // Construct a new query starting at this document,
                // get the next 25 cities.
                next = db.collection("cities")
                        .orderBy("population")
                        .startAfter(lastVisible)
                        .limit(25);

            }
        });         
 }

Now just call the loadCities() method whenever you need to load more cities.

Answer 6

You can achieve it by using Firebase database paging library as below code... In this code, I have shown Post as an data model item and PostViewHolder as ViewHolder

        //Initialize RecyclerView
        mRecyclerView = findViewById(R.id.recycler_view);
        mRecyclerView.setHasFixedSize(true);

        LinearLayoutManager mManager = new LinearLayoutManager(this);
        mRecyclerView.setLayoutManager(mManager);

        //Initialize Database
        mDatabase = FirebaseDatabase.getInstance().getReference().child("posts");

        //Initialize PagedList Configuration
        PagedList.Config config = new PagedList.Config.Builder()
                .setEnablePlaceholders(false)
                .setPrefetchDistance(5)
                .setPageSize(10)
                .build();

        //Initialize FirebasePagingOptions
        DatabasePagingOptions<Post> options = new DatabasePagingOptions.Builder<Post>()
                .setLifecycleOwner(this)
                .setQuery(mDatabase, config, Post.class)
                .build();

        //Initialize Adapter
        mAdapter = new FirebaseRecyclerPagingAdapter<Post, PostViewHolder>(options) {
            @NonNull
            @Override
            public PostViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
                return new PostViewHolder(LayoutInflater.from(parent.getContext()).inflate(R.layout.item_list, parent, false));
            }

            @Override
            protected void onBindViewHolder(@NonNull PostViewHolder holder,
                                            int position,
                                            @NonNull Post model) {
                holder.setItem(model);
            }

            @Override
            protected void onLoadingStateChanged(@NonNull LoadingState state) {
                switch (state) {
                    case LOADING_INITIAL:
                    case LOADING_MORE:
                        // Do your loading animation
                        mSwipeRefreshLayout.setRefreshing(true);
                        break;

                    case LOADED:
                        // Stop Animation
                        mSwipeRefreshLayout.setRefreshing(false);
                        break;

                    case FINISHED:
                        //Reached end of Data set
                        mSwipeRefreshLayout.setRefreshing(false);
                        break;

                    case ERROR:
                        retry();
                        break;
                }
            }

            @Override
            protected void onError(@NonNull DatabaseError databaseError) {
                super.onError(databaseError);
                mSwipeRefreshLayout.setRefreshing(false);
                databaseError.toException().printStackTrace();
            }
        };

        //Set Adapter to RecyclerView
        mRecyclerView.setAdapter(mAdapter);

Just visit this below URL for reference https://firebaseopensource.com/projects/patilshreyas/firebaserecyclerpagination/app/readme.md/ Here you will find implementation of library which helps to implement Pagination of firebase data in RecyclerView

I hope this will help you!