Recyclerview is not updated with new Data

问题:

Hiy guys,

I have a fragment with a RecyclerViewin it. That RecyclerView is populated by a Firebase 'DatabaseReference' object and on that reference I have added a ValueListener as follows:

public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle
        savedInstanceState) {
    Log.d(TAG, "onCreateView");
    View view = inflater.inflate(R.layout.fragment_home, container, false);


   databaseReference.addValueEventListener(new ValueEventListener() {
               @Override
               public void onDataChange(DataSnapshot dataSnapshot) {
                   //Do something
               }

               @Override
               public void onCancelled(DatabaseError databaseError) {
                   // Getting Post failed, log a message
                   Log.w(TAG, "onCancelled", databaseError.toException());
               }
           });

         ItemRecyclerViewAdapter  adapter = new ItemRecyclerViewAdapter(activity, itemsDatabaseReference);
           adapter.setHasStableIds(true);
           // use a linear layout manager
          RecyclerView recyclerView = (RecyclerView) view.findViewById(R.id.recyclerview);
           recyclerView.setHasFixedSize(true);
           RecyclerView.LayoutManager layoutManager = new LinearLayoutManager(getActivity());
           recyclerView.setLayoutManager(layoutManager);
           DividerItemDecoration itemDecoration = new DividerItemDecoration(getContext(),
                   DividerItemDecoration.VERTICAL_LIST);
           recyclerView.addItemDecoration(itemDecoration);
           recyclerView.setAdapter(adapter);

    return view;
}

ItemRecyclerViewAdapter extends FirebaseRecyclerAdapter. The problem is that onDataChange happens after onResume so that at times the recycler is empty. What I can't understand is the fact that the recycler view is not always empty. Sometimes data are shown and sometimes not.

Thanks

回答1:

I think if you are using FirebaseRecyclerAdapter (or any class extended from that) as your RecyclerView adapter, you should set recyclerView.setHasFixedSize(false). So the recyclerView knew that data is constantly updated.

回答2:

Actually onResume(); is strictly bound with activity onResume();

If you are using viewpager then there is a method in fragment

 @Override
public void setUserVisibleHint(boolean isVisibleToUser) {
    super.setUserVisibleHint(isVisibleToUser);
    //do your logic . updating recycler view
}

if you are infalting in framelayout

then you can update in onViewCreated();