Question

我正在尝试显示用户从Firebase Database获得的最后一次会话列表。我正在使用嵌套的ValueEventListeners，以便我首先检索当前用户所涉及的chatroom IDs，然后根据这些ID，我获得最新的活动（来自该聊天室）并相应地创建一个对象被添加到ListView。

创建片段后，chatRooms列表已正确加载，如here所示。然而，如果另一个用户向当前用户发送另一条消息，最后一个项目会重复（不知何故，它会获得上一个标记，但最新消息中的文本相同），如here所示。

导致此行为的原因是什么？

MyChatsFragment.java

public class MyChatsFragment extends Fragment {

private ListView listView;

public MyChatsFragment() {
    // Required empty public constructor
}


@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

}

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    // Inflate the layout for this fragment
    View view = inflater.inflate(R.layout.fragment_my_chats, container, false);

    FirebaseDatabase database = FirebaseDatabase.getInstance();
    final DatabaseReference databaseReference = database.getReference();
    final DatabaseReference ChatMembersReference = databaseReference.child("chat_members");

    final FirebaseUser currentUser = FirebaseAuth.getInstance().getCurrentUser();
    if (currentUser != null) {
        final String currentUID = currentUser.getUid();

        listView = (ListView) view.findViewById(R.id.MyChatsList);


        Query filterQuery = ChatMembersReference.orderByChild(currentUID).equalTo(true);
        filterQuery.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(DataSnapshot dataSnapshot) {
                final List<ChatInfo> my_chats = new ArrayList<ChatInfo>();

                for (DataSnapshot child : dataSnapshot.getChildren()) {
                    final String ChatRoom = child.getKey();
                    // ADD VALUE EVENT LISTENER
                    databaseReference.child("chat_info").child(ChatRoom).child("lastStamp").addValueEventListener(new ValueEventListener() {
                        @Override
                        public void onDataChange(DataSnapshot dataSnapshot) {
                            long lastMessageStamp = (long) dataSnapshot.getValue();

                            ChatInfo currentChatInfo = new ChatInfo(ChatRoom, lastMessageStamp);
                            my_chats.add(currentChatInfo);
                            // HERE WE HAVE TO SORT
                            if (my_chats.size() > 1) {
                                Collections.sort(my_chats, new Comparator<ChatInfo>() {
                                    @Override
                                    public int compare(ChatInfo o1, ChatInfo o2) {
                                        if (o1.getLastMessageTimeStamp() < o2.getLastMessageTimeStamp()) {
                                            return -1;
                                        } else if (o1.getLastMessageTimeStamp() > o2.getLastMessageTimeStamp()) {
                                            return 1;
                                        }
                                        return 0;
                                    }
                                });
                            }
                            Collections.reverse(my_chats);

                            MyChatsAdapter myChatsAdapter = new MyChatsAdapter(getActivity(), my_chats);
                            listView.setAdapter(myChatsAdapter);
                        }

                        @Override
                        public void onCancelled(DatabaseError databaseError) {

                        }
                    });
                }
            }

            @Override
            public void onCancelled(DatabaseError databaseError) {

            }
        });
      }
    return view;
    }


   }

MyChatsAdapter.java ：check this gist please

ListView在刷新时复制最后一项

0 个答案: