android - 如何设置添加 child 时调用的onChildAdded

Question

public class ChatsFragment extends Fragment {

FirebaseDatabase database;
DatabaseReference myRef;
List<ListData> list;
RecyclerView recyclerview;
TextView badge;
String name, message, nameCaps;
int id, user_id;
DatabaseHelper databaseHelper;

public View onCreateView(LayoutInflater inflater, ViewGroup group, Bundle b) {
    View view = inflater.inflate(R.layout.fragment_chats, group, false);
    recyclerview = view.findViewById(R.id.rview);
    badge = view.findViewById(R.id.badge);
    database = FirebaseDatabase.getInstance();
    myRef = database.getReference("message");
    list = new ArrayList<>();
    databaseHelper = new DatabaseHelper(getContext());
    myRef.addChildEventListener(new ChildEventListener() {
        @Override
        public void onChildAdded(DataSnapshot dataSnapshot, String s) {
            UserDetails userdetails = dataSnapshot.getValue(UserDetails.class);
            name = userdetails.getName();
            message = userdetails.getMessage();
            id = userdetails.getId();
            user_id = userdetails.getUser_id();
            nameCaps = name.substring(0, 1).toUpperCase() + name.substring(1);
            if (databaseHelper.checkUserID(user_id)) {
                databaseHelper.updateMsg(nameCaps, message, user_id);
            } else {
                databaseHelper.insertData(nameCaps, message, id, user_id);
            }
            list = databaseHelper.getData();
            RecyclerViewAdapter recycler = new RecyclerViewAdapter(list);
            RecyclerView.LayoutManager layoutManager = new LinearLayoutManager(getContext());
            recyclerview.setLayoutManager(layoutManager);
            recyclerview.setItemAnimator(new DefaultItemAnimator());
            recyclerview.setAdapter(recycler);
        }

        @Override
        public void onChildChanged(DataSnapshot dataSnapshot, String s) {
            UserDetails userdetails = dataSnapshot.getValue(UserDetails.class);
            name = userdetails.getName();
            message = userdetails.getMessage();
            id = userdetails.getId();
            nameCaps = name.substring(0, 1).toUpperCase() + name.substring(1);
            databaseHelper.updateData(nameCaps, message, id);

        }

        @Override
        public void onChildRemoved(DataSnapshot dataSnapshot) {
            UserDetails userdetails = dataSnapshot.getValue(UserDetails.class);
            id = userdetails.getId();
            databaseHelper.deleteData(id);
        }

        @Override
        public void onChildMoved(DataSnapshot dataSnapshot, String s) {

        }

        @Override
        public void onCancelled(DatabaseError databaseError) {

        }
    });
    return view;
}

这是我的代码。当添加一个 child 时，我将其保存在 sqlite 数据库中，并从数据库中获取数据并加载到 recyclerview 中，但是 onChildAdded() 方法调用每个当我打开应用程序时。如何设置当我添加一个 child 然后调用 onChildAdded() 否则它不会调用 onChildAdded()

Answer 1

没有这种查找方式，因为它总是返回给您 Firebase 上存在的所有相关数据。根据我的研究和知识，没有解决方案可以限制它。

有一种方法可以做到这一点:

对我来说，逻辑是要有值——例如“status”——在决定它是真的新记录还是旧记录之前需要对其进行验证，然后我将“status”设置为不同的值，这样我就不会下次得到它:

@Override
    public void onChildAdded(DataSnapshot dataSnapshot, String previousChildKey) {

            if(dataSnapshot.hasChildren()) {

                String Id = (String) dataSnapshot.child("user_id").getValue();
                String status = (String) dataSnapshot.child("status").getValue();

                if (Id != null && Id.equals(storedId) && status != null && status.equals("created")) {
                    Log.d("INCOMING_REQUEST", "This is for you!");
                    sessionsRef.child(dataSnapshot.getKey()).child("status").setValue("received");
                }

            }


    }

谢谢，如果需要更多请告诉我!!