无法在 RecyclerView 中显示来自 firebase 的特定数据

Question

I managed to retrieve the data from the firebase and use a recylcerview and a holder to display them. I only need to retrieve data from certain nodes from the firebase. Nodes that are not taken by id but by an inside name:

The problem is that it only displays my data for certain nodes, but it displays them in the order in which they are found in the database. This leaves empty rows in the recyclerview. (for example if the second node is the one you are looking for, put an empty card then the one with data):

The function by which I take the data from the firebase depending on the name is:

 private void LoadFeedbackMuzee(String denumire) { options = new FirebaseRecyclerOptions.Builder<Parere>().setQuery(refM, Parere.class).build(); adapterFM = new FirebaseRecyclerAdapter<Parere, MyViewHolderRecenziiM>(options) { @Override protected void onBindViewHolder(@NonNull MyViewHolderRecenziiM holder, int position, @NonNull Parere model) { if (model.getDenumire().equals(denumire)) { String userId = model.getIdUser(); int photo = model.getLevel(); holder.parere.setText(model.getIntrb1()); userRef.child(userId).addValueEventListener(new ValueEventListener() { @Override public void onDataChange(@NonNull DataSnapshot snapshot) { if (snapshot.hasChild("fullname")) { String nume = snapshot.child("fullname").getValue().toString(); holder.username.setText(nume); } } @Override public void onCancelled(@NonNull DatabaseError error) { } }); if (photo == 1) { holder.image.setImageResource(R.drawable.terrible); } else if (photo == 2) { holder.image.setImageResource(R.drawable.bad); } else if (photo == 3) { holder.image.setImageResource(R.drawable.okay); } else if (photo == 4) { holder.image.setImageResource(R.drawable.good); } else if (photo == 5) { holder.image.setImageResource(R.drawable.great); } } } @NonNull @Override public MyViewHolderRecenziiM onCreateViewHolder(@NonNull ViewGroup parent, int viewType) { View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.parere_layout, parent, false); return new MyViewHolderRecenziiM(view); } }; adapterFM.startListening(); recyclerViewR.setAdapter(adapterFM); }

Answer 1

This is happening because you are doing these things in the onBindViewHolder . So in this case what happens is, if your condition matches then the data is binded otherwise the item in the recycler is left empty means the item layout is just inflated and if you know the working of the adapter then you must be knowing that the size of the list is used to inflate the number of items (parere_layout) in recycler view. So the adapter inflates the layout but when it comes to binding (in onBindViewHolder) the data like userName and photo then if your defined condition matches then it binds otherwise the fields are left empty. Hope now you understand the working of the adapter.

So the solution is:

(1) that either you make itemView Visible for only your condition and make its visibility gone for unwanted condition. Sample code below

holder.itemView.setVisibility(View.GONE);// to make it's visibility gone
 holder.itemView.setVisibility(View.VISIBLE);// to make it visible when condition matches.

(2) Recommended Solution: The second solution that I can see is that, if you filter your data before passing it to the adapter then your problem will be solved. By filtering, I mean that after fetching data from the database you just make another list in which you add only that data what you want to be shown, so in this way, your adapter code will be more cleaner and also your problem will be solved simultaneously.

Feel free to ask if something is unclear. And kindly mark this as the correct answer if it helps you so that in the future this answer can also help any other needy.

Answer 2

I THINK you have to do something to your views if data doesn't exist at a node but is still being looped through. So you would do something like this where you would make the views GONE if the denumire doesn't.equal(model.getDenumire) and VISIBLE if it does. And do the same if the snapshot.hasChild(fullname) doesn't have the name so like:

   if (model.getDenumire().equals(denmuire) {
            GETDATA()
            if (snapshot.hasChild(fullname) {

                holder.image.setVisibility(View.VISIBLE);
                holder.name..setVisibility(View.VISIBLE);
                holder.name.setName(Name)
                   if (photo == 1) {
                    holder.image.setImageResource(R.drawable.terrible);
                } else if (photo == 2) {
                    holder.image.setImageResource(R.drawable.bad);
                } else if (photo == 3) {
                    holder.image.setImageResource(R.drawable.okay);
                } else if (photo == 4) {
                    holder.image.setImageResource(R.drawable.good);
                } else if (photo == 5) {
                    holder.image.setImageResource(R.drawable.great);
                }

            }else{
                holder.image.setVisibility(View.GONE);
                holder.name.setVisibility(View.GONE);
            }

        } else{
            holder.image.setVisibility(View.GONE);
            holder.name.setVisibility(View.GONE);
            etc...
        }