具有异步回调的DiffUtil仅显示列表一次，并且不会更新

Question

我正在使用DiffUtil异步回调来更新我的列表。 问题在于它在第一次调用时仅显示一次数据集。以后，当数据集更新时，列表仅显示最初显示的项目。因此问题在于数据集会更新，但列表会停留在其第一个状态。（使用最初创建的项目）

通过用户启动的按钮单击来更新数据集，其外观如下：

   private void updateUsersList() {
        @Override
        public void onResponse(JSONArray response) { // the JSON ARRAY response of user ids ["uid1", "uid334", "uid1123"]

            for (int i = 0; i < response.length(); i++) {
                try {
                    String userKey = response.get(i).toString(); // the currently iterated user id
                    final DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference();
                    DatabaseReference userKeyRef = rootRef.child("users").child(userKey); // reference to currently iterated user
                    ValueEventListener listener = new ValueEventListener() {
                    @Override
                    public void onDataChange(DataSnapshot dataSnapshot) {
                        myDataset.add(new User(dataSnapshot.getKey(), dataSnapshot.child("imageUrl").getValue().toString())); //add new user: id and image url
                        mAdapter.updateList(myDataset); 
                   }
                   @Override
                   public void onCancelled(@NonNull DatabaseError databaseError) {
                   Log.d(TAG, databaseError.getMessage());
                   }
                  };
                  userKeyRef.addListenerForSingleValueEvent(listener);
              }
              catch (JSONException e) { Log.d(TAG, "message " + e); }
           }
   }

这是我的使用异步DiffUtil的适配器：

公共类MyAdapter扩展了RecyclerView.Adapter {

    private AsyncListDiffer<User> mAsyncListDiffer;

    public static class MyViewHolder extends RecyclerView.ViewHolder {

        public TextView singleItemTextView;
        public ImageView singleItemImage;
        public View layout;
        public ConstraintLayout constraintLayout;

        public MyViewHolder(View v) {
            super(v);
            layout = v;
            singleItemImage = (ImageView) v.findViewById(R.id.icon);
            singleItemTextView = (TextView) v.findViewById(R.id.singleitemtv);
            constraintLayout = (ConstraintLayout) v.findViewById(R.id.nbConstraintLayout);
        }
    }

    // Provide a suitable constructor (depends on the kind of dataset)
    public MyAdapter() {
        DiffUtil.ItemCallback<User> diffUtilCallback = new DiffUtil.ItemCallback<User>() {

            @Override
            public boolean areItemsTheSame(@NonNull User newUser, @NonNull User oldUser) {
                return newUser.getUserId().equals(oldUser.getUserId());
            }

            @Override
            public boolean areContentsTheSame(@NonNull User newUser, @NonNull User oldUser) {
                return newUser.equals(oldUser);
            }
        };
        mAsyncListDiffer = new AsyncListDiffer<>(this, diffUtilCallback);
    }

    // Create new views (invoked by the layout manager)
    @Override
    public MyAdapter.MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View v = LayoutInflater.from(parent.getContext()).inflate(R.layout.nb_image_view, parent, false);
        MyViewHolder vh = new MyViewHolder(v);
        return vh;
    }

    @Override
    public void onBindViewHolder(final MyViewHolder holder, final int position) {
        User user = mAsyncListDiffer.getCurrentList().get(position);
        Uri userImage = user.getImageUrl();
        Log.d("test123", "user uri: " + userImage.toString());
        holder.singleItemTextView.setText(user.getUserId());

        Glide.with(holder.itemView.getContext() /* context */)
                .load(userImage)
                .into(holder.singleItemImage);

        holder.constraintLayout.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Context context = v.getContext();
                Intent intent = new Intent(v.getContext(), DisplayUserActivity.class);
                context.startActivity(intent);
            }
        });
    }

    @Override
    public int getItemCount() {
        return mAsyncListDiffer.getCurrentList().size();
    }

    public void updateList(ArrayList<User> newList) {
        mAsyncListDiffer.submitList(newList);
    }

}

那为什么我的数据集会更新，但列表仅停留在第一次更新？