如何使firebase回收器适配器在某些条件下显示特定数据

Question

我需要知道如何在特定条件下显示数据，即如果用户的 showGigCount 大于 0，则显示用户的数据。我使用 Query 来实现这一点，但通过使用它，所有数据都会消失。如果标记的节点变为零，则不得仅显示该特定用户的数据。下面是我的代码。谢谢你们

MyViewHolder.Class

public MyViewHolder(@NonNull @NotNull 查看 itemView) { 超级（项目视图）；

    previewLink =  itemView.findViewById(R.id.uev);
    geglink = (TextView) itemView.findViewById(R.id.rcvGigLink);
    userName = (TextView) itemView.findViewById(R.id.rcvName);
    userAbout = (TextView) itemView.findViewById(R.id.rcvAbout);
    v = itemView;

DashboardActivity.class

fAuth = FirebaseAuth.getInstance();
        firebaseDatabase = FirebaseDatabase.getInstance();
        dRef = FirebaseDatabase.getInstance().getReference("Users");

        recyclerView = findViewById(R.id.dashboardRCV);
        recyclerView.setLayoutManager(new LinearLayoutManager(this));
      LoadData();

    }

    private void LoadData() {
        options = new FirebaseRecyclerOptions.Builder<ModelClass>()
                .setQuery(dRef, ModelClass.class)
                .build();
        adapter = new FirebaseRecyclerAdapter<ModelClass, MyViewHolder>(options) {
            @Override
            protected void onBindViewHolder(@NonNull MyViewHolder holder, int position, @NonNull ModelClass model) {

           
                
                holder.previewLink.setURL(model.getGig(), new URLEmbeddedView.OnLoadURLListener() {
                    @Override
                    public void onLoadURLCompleted(URLEmbeddedData data) {

                        holder.previewLink.title(data.getTitle());
                        holder.previewLink.description(data.getDescription());
                        holder.previewLink.host(data.getHost());
                        holder.previewLink.thumbnail(data.getThumbnailURL());
                        holder.previewLink.favor(data.getFavorURL());
                    }
                });


                //This will hide the gig if its showGigCount becomes 0
                Query query = dRef.orderByChild("showGigCount").equalTo(0);
                ValueEventListener valueEventListener = new ValueEventListener() {
                    @Override
                    public void onDataChange(@NonNull DataSnapshot snapshot) {
                        if (snapshot.exists()){

                            holder.previewLink.setVisibility(View.GONE);
                        }
                    }
                    @Override
                    public void onCancelled(@NonNull DatabaseError error) {
                    }
                };
                query.addListenerForSingleValueEvent(valueEventListener);



            }

            @NonNull
            @Override
            public MyViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
                View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.recyclerview_layout, parent, false);
                return new MyViewHolder(view);
            }
        };
        adapter.startListening();
        recyclerView.setAdapter(adapter);

Answer 1

如果用户的 showGigCount 大于 0，则显示用户的数据。

为此，请使用以下代码行：

DatabaseReference db = FirebaseDatabase.getInstance().getReference();
DatabaseReference usersRef = db.child("Users");
Query queryByShowGigCount = usersRef.orderByChild("showGigCount").startAt(0).startAt(1);
options = new FirebaseRecyclerOptions.Builder<ModelClass>()
            .setQuery(queryByShowGigCount, ModelClass.class)
            .build();

如您所见，解决此问题的关键是使用Query#startAt() 方法。