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 the code I thought would work

  private void getVideos() {

        Query videosQuery = FirebaseUtil.getVideosRef();
        videosQuery.startAt(0);
        videosQuery.endAt(1);

        ChildEventListener videosChildEventListener = new ChildEventListener() {
            @Override
            public void onChildAdded(DataSnapshot dataSnapshot, String s) {
                String date = dataSnapshot.getKey();
                String temp = date;
            }

            @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) {

                Log.d(tag, "database error");
            }
        };


        ValueEventListener videoValueEventListener = new ValueEventListener() {
            @Override
            public void onDataChange(DataSnapshot dataSnapshot) {
                String date = dataSnapshot.getKey();
                String temp = date;

               long count =  dataSnapshot.getChildrenCount();
                String value = dataSnapshot.getValue().toString();
                temp = value;
            }

            @Override
            public void onCancelled(DatabaseError databaseError) {
                Log.d(tag, "database error");
            }
        };
//        videosQuery.addChildEventListener(videosChildEventListener);
        videosQuery.addValueEventListener(videoValueEventListener);

    }

But above code retrieves entire list of videos instead of limited videos. How can pagination be implemented.

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);
        }
    }