android - 为什么我只在片段中显示我的用户列表，当我更改片段并返回时，它不会显示用户列表

Question

为什么我只在片段中显示我的用户列表，当我更改片段并返回时，它不会显示用户列表。

该功能正在运行，但我不知道为什么只显示一次。

private RecyclerView recyclerView;
FirebaseUser firebaseUser;
private MessageListAdapter messageListAdapter;
private List<ChatListModel> usersList;
private List<UserModel> mUsers;

public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
    View view = inflater.inflate(R.layout.fragment_message, container,false);
    recyclerView = view.findViewById(R.id.recycler_view);
    recyclerView.setHasFixedSize(true);
    recyclerView.setLayoutManager(new LinearLayoutManager(getContext()));

    firebaseUser = FirebaseAuth.getInstance().getCurrentUser();
    usersList = new ArrayList<>();

    DatabaseReference reference = 
    FirebaseDatabase.getInstance().getReference("Chatlist").child(firebaseUser.getUid());
    reference.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                usersList.clear();
                for(DataSnapshot snapshot : dataSnapshot.getChildren()){
                    ChatListModel chatListModel = snapshot.getValue(ChatListModel.class);
                    usersList.add(chatListModel);
                }
                chatList();
            }

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

            }
        });


        return view;
}

private void chatList() {
        mUsers = new ArrayList<>();
        DatabaseReference reference = FirebaseDatabase.getInstance().getReference("Users");
        reference.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                mUsers.clear();
                for(DataSnapshot snapshot : dataSnapshot.getChildren()){
                    UserModel userModel = snapshot.getValue(UserModel.class);
                    for(ChatListModel chatListModel : usersList){
                        if(userModel.getId().equals(chatListModel.getId())){
                            mUsers.add(userModel);
                        }
                    }
                }
                messageListAdapter = new MessageListAdapter(getContext(), mUsers);
                recyclerView.setAdapter(messageListAdapter);
            }

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

            }
        });
    }

我从来没有遇到任何崩溃，只需更改其他片段并支持它。片段将显示空白页。

标签： androidandroid-fragmentsfragmentandroid-fragmentactivity