如何进行 Firebase 聊天分页？答案

【问题标题】：How to do Firebase chat pagination?如何进行 Firebase 聊天分页？
【发布时间】：2019-02-20 12:40:18
【问题描述】：

我在从 firebase DB 获取列表时遇到了这个问题，但我没有得到方法。

要求是 - 通过分页从 Db 获取 Firebase 聊天列表

【问题讨论】：

【解决方案1】：

在这里，我完成了 Firebase-Chat-Pagination。检查一下。它可能对你有帮助。

    mUserRefValueEventListener = mConversationRef.child(mLocation)
            .limitToLast(TOTAL_ITEM_EACH_LOAD)
            .orderByKey()
            .addValueEventListener(new ValueEventListener() {
                @Override
                public void onDataChange(DataSnapshot dataSnapshot) {
                    // It should be null when new meesage sent by own
                    mLastDataSnapshot = null;
                    if (dataSnapshot.exists()) {
                        mChatList.clear();
                        for (DataSnapshot readDataSnapshot : dataSnapshot.getChildren()) {
                            ChatResponse chatModel = readDataSnapshot.getValue(ChatResponse.class);
                            if (chatModel != null) {
                                mChatList.add(chatModel);
                            }
                            // We need First DataSnapshot for pagination
                            if (mLastDataSnapshot == null) {
                                mLastDataSnapshot = readDataSnapshot;
                            }

                        }
                        mView.onFetchMessagesSuccess(mChatList);
                    }
                }

                @Override
                public void onCancelled(DatabaseError databaseError) {

                }
            });

}

 public void loadMoreDataPagination() {

    if (mLastDataSnapshot != null && (mTotalCount == 0 || mView.getChatMessageCount() < mTotalCount)) {
        mUserRefValueEventListener = mConversationRef.child(mLocation)
                .orderByKey()
                .endAt(mLastDataSnapshot.getKey())
                .limitToLast(TOTAL_ITEM_EACH_LOAD)
                .addValueEventListener(new ValueEventListener() {
                    @Override
                    public void onDataChange(DataSnapshot dataSnapshot) {


                        if (dataSnapshot.exists()) {
                            mChatList.clear();
                            for (DataSnapshot readDataSnapshot : dataSnapshot.getChildren()) {
                                ChatResponse chatModel = readDataSnapshot.getValue(ChatResponse.class);
                                if (chatModel != null) {
                                    mChatList.add(chatModel);
                                }
                                // We need Last DataSnapshot for pagination while load more
                                if (mChatList.size() == 1) {
                                    mLastDataSnapshot = readDataSnapshot;
                                }
                            }
                            // One item duplicates from last list so need to Remove it
                            mChatList.remove(mChatList.size() - 1);
                            mView.onFetchLoadMoreSuccess(mChatList, mTotalCount);

                        }
                    }

                    @Override
                    public void onCancelled(DatabaseError databaseError) {
                        mView.hideLoading();
                    }
                });
    }
}```

【讨论】：