Firebase安卓分页

Question

我正在构建一个应用程序,它将显示存储在firebase上的视频.视频列表需要分页,一次最多可获取20个视频.

这是我认为可行的代码

  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);

    }

但上面的代码检索整个视频列表而不是有限的视频.如何实施分页.

Answer 1

下面是我用于分页的代码,它首先显示最新的节点.

      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

我有以下方法通过Firebase实时数据库节点进行分页：

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;
            }
        });
    }

每当我到达分页数据的底部时，我都会调用getUsers(mAdapter.getLastItemId());，然后它将带来下一组记录。

我已经为此编写了带有开源示例应用程序的完整指南，您可以在https://blog.shajeelafzal.com/2017/12/13/firebase-realtime-database-pagination-guide-using-recyclerview/中查看