从firebase

Question

我想在获取数据后更新我的列表，但是当我尝试时，没有任何反应，仍然显示相同的旧数据。我尝试异步获取数据，但同样的问题发生了。 这是代码。

public class myFragment extends ListFragment{
private DatabaseReference database = FirebaseDatabase.getInstance().getReference();
ArrayAdapter<Event> adapter;

List<Event> eventsList = new ArrayList<Event>();
Event[] events = {
        new Event(...), //Test data
        new Event(...),
        new Event(...)
};

public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
    View view = inflater.inflate(R.layout.fragment_home, container, false); //Custom view
    return view;
}

@Override
public void onActivityCreated(Bundle savedInstanceState) {
    super.onActivityCreated(savedInstanceState);
    adapter = new EventsAdapter(getActivity(), events);
    setListAdapter(adapter);

    database.child("Events").addValueEventListener(new ValueEventListener() {
        public void onDataChange(DataSnapshot dataSnapshot) {
            for (DataSnapshot s : dataSnapshot.getChildren()) {
                Event event = s.getValue(Event.class);
                eventsList.add(event);
                //adapter.add(event); crashes the app for some reason
            }
            events = eventsList.toArray(new Event[eventsList.size()]);
            adapter.notifyDataSetChanged();
        }

        public void onCancelled(DatabaseError databaseError) {
        }
    });
}

public void onListItemClick(ListView l, View v, int position, long id) {...}
}

我无法在代码中找到错误，我该如何解决？

Answer 1

要解决此问题，您需要使用ChildEventListener代替addValueEventListener。

database.child("Events").addChildEventListener(new ValueEventListener() {
    public void onDataChange(DataSnapshot dataSnapshot) {
        for (DataSnapshot s : dataSnapshot.getChildren()) {
             Event event = s.getValue(Event.class);
             eventsList.add(event);
             //adapter.add(event); crashes the app for some reason
        }
        events = eventsList.toArray(new Event[eventsList.size()]);
        adapter.notifyDataSetChanged();
    }

    public void onCancelled(DatabaseError databaseError) {
    }
});

Answer 2

当您希望修改数据时，请不要使用数组，请使用ArrayLists。