再次打开片段时 Recyclerview 变空

Question

我在片段中有一个回收视图当我按返回键转到上一个 activity 然后返回时，回收器视图变空了

我试着把 adapter.startListening();到 onStart() 还尝试将 stopListening() 放到 onStop()

当我第一次进入片段或关闭应用程序并再次打开它时，回收器视图内容显示，但是当我按下后退按钮并再次返回片段时，回收器视图的所有内容都得到了空

这是我的代码：

public class EnrolledAboutEditFragment extends Fragment {

private FirebaseAuth mAuth;
private String mCurrentUserId;
private DatabaseReference mRootRef;
private RecyclerView mRecycler;
FirebaseRecyclerOptions<ModelAboutEnrolled> options;
FirebaseRecyclerAdapter<ModelAboutEnrolled, ViewHolderAboutEnrolled> adapter;

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


@Override
public View onCreateView(LayoutInflater inflater, final ViewGroup container,
                         Bundle savedInstanceState) {
    mAuth = FirebaseAuth.getInstance();
    mCurrentUserId = mAuth.getCurrentUser().getUid();
    mRootRef = FirebaseDatabase.getInstance().getReference();
    mRootRef.keepSynced(true);

    mView = inflater.inflate(R.layout.fragment_enrolled_about_edit,container,false);
    mRecycler = mView.findViewById(R.id.f_about_recycler_view);
    mRecycler.setHasFixedSize(true);

    mRootRef.child("Users").child(mCurrentUserId).addValueEventListener(new ValueEventListener() {
        @Override
        public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
            String username = dataSnapshot.child("username").getValue().toString();
            adapterFunction();
        }

        @Override
        public void onCancelled(@NonNull DatabaseError databaseError) { }
    });

}


public void adapterFunction(){
    DatabaseReference reference = mRootRef.child("Contents").child(username);
    options = new FirebaseRecyclerOptions.Builder<ModelAboutEnrolled>()
            .setQuery(reference,ModelAboutEnrolled.class).build();

    adapter = new FirebaseRecyclerAdapter<ModelAboutEnrolled, ViewHolderAboutEnrolled>(options) {
        @Override
        protected void onBindViewHolder(@NonNull final ViewHolderAboutEnrolled holder, int position, @NonNull final ModelAboutEnrolled model) {
            Picasso.get().load(model.getImage()).into(holder.image);
        }

        @NonNull
        @Override
        public ViewHolderAboutEnrolled onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
            View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.layout_about_enrolled,parent,false);
            return new ViewHolderAboutEnrolled(view);
        }
    };

    LinearLayoutManager llm = new LinearLayoutManager(getContext(), LinearLayoutManager.HORIZONTAL, false);
    mRecycler.setLayoutManager(llm);
    adapter.startListening();
    mRecycler.setAdapter(adapter);
}

}

Answer 1

删除您的 setHasFixedSize() 方法。

再次打开片段时 Recyclerview 变空

Recycler View gets empty when the fragment s opened again

android

android-fragments

firebase

firebase-realtime-database

firebaseui