java - 等待 Firestore 数据被检索

Question

I need after inner foreach finish and add all data in list then send to interface

but when but this line " view.setOrders(orderList); " below " orderList.add(order); "

my code run okye but not that is not performance , I need best way to collection list then send to interface ..

public ListenerRegistration getOrders() {

        view.showLoading();

       ListenerRegistration listenerRegistration = refOrders.addSnapshotListener((queryDocumentSnapshots, e) -> {

            view.hideLoading();

            if (e != null) {
                view.onErrorMessage(e.getMessage());
            } else {
                List<Order> orderList = new ArrayList<>();
                for (QueryDocumentSnapshot snapshot : queryDocumentSnapshots) {

                    Order order = snapshot.toObject(Order.class);
                    order.setOrderId(snapshot.getId());

                    refUsers.document(order.getPhone()).get().addOnCompleteListener(new OnCompleteListener<DocumentSnapshot>() {
                        @Override
                        public void onComplete(@NonNull Task<DocumentSnapshot> task) {

                            if (task.isSuccessful()) {
                                User user = task.getResult().toObject(User.class);
                                order.setName(user.getName());
                                order.setAddress(user.getAddress());
                                orderList.add(order);

                            }


                        }
                    });
                }

                //Here Back List size = 0
                view.setOrders(orderList);


            }
        });

       return listenerRegistration;

    }

Answer 1

自 get()方法是异步的，这意味着 CompletionListener 之后的代码将首先执行，然后在检索数据后执行 listener将被处决。

因此，要解决该问题，请添加以下行 view.setOrders(orderList);里面CompletionListener

if (task.isSuccessful()) {
 User user = task.getResult().toObject(User.class); 
 order.setName(user.getName());
 order.setAddress(user.getAddress());
 orderList.add(order);
view.setOrders(orderList);