需要这样做：
基本上，我希望Firestore =>集合“ order” =>每个文档上都有customerid和productid的文档=> onSuccess =>添加到OrderPOJOList =>调用getCustomerName（）然后getProductName（）=> 按顺序获取名称 =>添加到相应的ArrayList =>最后，将来自三个arraylist的所有数据组合在一起（OrderPOJOList，CustomerName，ProductName）到 CurrentOrderPOJOList =>设置为Adapter。
问题： getCustomerName（）和getProductName（）中的两个侦听器异步运行，并将Name随机添加到 arrayList ......我想要的只是以顺序在适配器上显示数据，但有时要命名由于列表生成器异步运行，因此列表上可以交换。
我应该怎么做才能顺序显示来自Firestore的客户和产品名称？
public class CurrentOrders extends AppCompatActivity {
private List<CurrentOrdersPOJO> currentOrdersPOJOList;
private List<OrderPOJO> orderPOJOList;
private FirebaseFirestore firebaseFirestore;
private String DocId, Area, cname, pname;
private OrderPOJO orderPOJO;
private CurrentOrdersPOJO currentOrdersPOJO;
private int count = -1, count1 = -1, i;
private RecyclerView recyclerView;
private List<String> customerName, productName;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_current_orders);
//Current User Unique ID
DocId = getIntent().getStringExtra("DocumentId");
Area = getIntent().getStringExtra("Area");
Log.w("ReachedCurrentOrders", "Doc Id: " + DocId + "\nArea: " + Area);
currentOrdersPOJOList = new ArrayList<>();
customerName = new ArrayList<String>();
productName = new ArrayList<String>();
orderPOJOList = new ArrayList<>();
recyclerView = findViewById(R.id.activity_current_order_recyclerView);
firebaseFirestore = FirebaseFirestore.getInstance();
recyclerView.setLayoutManager(new LinearLayoutManager(this, LinearLayoutManager.VERTICAL, false));
recyclerView.addItemDecoration(new DividerItemDecoration(this, LinearLayoutManager.VERTICAL));
firebaseFirestore.collection("order")
.whereEqualTo("area", Area)
.whereEqualTo("status", "active")
.get()
.addOnSuccessListener(new OnSuccessListener<QuerySnapshot>() {
@Override
public void onSuccess(final QuerySnapshot queryDocumentSnapshots) {
if (!queryDocumentSnapshots.isEmpty()) {
for (final QueryDocumentSnapshot queryDocumentSnapshot : queryDocumentSnapshots) {
count++;
}
for (final QueryDocumentSnapshot queryDocumentSnapshot : queryDocumentSnapshots) {
orderPOJO = queryDocumentSnapshot.toObject(OrderPOJO.class);
orderPOJOList.add(orderPOJO);
Log.d("Tagging", "The Customer UID: " + orderPOJO.getC_uid() + "\nThe Product Doc ID: " + orderPOJO.getP_docid());
count1++;
if (count == count1) {
getCustomerName();
}
}//endof for loop
} else {
Toast.makeText(CurrentOrders.this, "No Orders in Your Area", Toast.LENGTH_SHORT).show();
Log.d("CurrentOrder", "Exception Here");
}
}
});
}//endofOnCreate
public void getCustomerName() {
count1 = -1;
//Getting Customer Name from ID
for (i = 0; i <= count; i++) {
firebaseFirestore.collection("customer").document(orderPOJOList.get(i).getC_uid()).get().addOnSuccessListener(new OnSuccessListener<DocumentSnapshot>() {
@Override
public void onSuccess(DocumentSnapshot documentSnapshot) {
if (documentSnapshot.exists()) {
cname = documentSnapshot.getString("name");
customerName.add(cname);
count1++;
if (count1 == count) {
getProductName();
}
} else {
Log.d("CurrentOrders", "Exception Here" + documentSnapshot.exists());
}
}
});
}
}//end of function
public void getProductName() {
count1 = -1;
//Product Getting Name
for (i = 0; i <= count; i++) {
firebaseFirestore.collection("product").document(orderPOJOList.get(i).getP_docid()).get().addOnSuccessListener(new OnSuccessListener<DocumentSnapshot>() {
@Override
public void onSuccess(DocumentSnapshot documentSnapshot) {
if (documentSnapshot.exists()) {
pname = documentSnapshot.getString("name");
productName.add(pname);
count1++;
if (count1 == count) {
callAdapter();
}
} else {
Log.d("CurrentOrders", "Exception Here" + documentSnapshot.exists());
}
}
});
}
}//endofFunction
public void callAdapter() {
for (int i = 0; i <= count; i++) {
currentOrdersPOJO = new CurrentOrdersPOJO(customerName.get(i), orderPOJOList.get(i).getComplete_address(),
productName.get(i), orderPOJOList.get(i).getQuantity(), orderPOJOList.get(i).getStatus(), orderPOJOList.get(i).getArea(), orderPOJOList.get(i).getO_date());
currentOrdersPOJOList.add(currentOrdersPOJO);
}
recyclerView.setAdapter(new CurrentOrdersAdapter(currentOrdersPOJOList, CurrentOrders.this));
}//endofFunction
}//endofclass
[活动列表的屏幕快照随时间变化] [1]
[1]: https://i.stack.imgur.com/X48JF.jpg
答案 0 :(得分：1)
在另一个thread上也提出了类似的问题，由于该方法本身是一个任务，因此您似乎可以同步返回数据，您可以尝试使用Taks.await（task）方法来等待该操作。操作结束，也许这就是您要寻找的答案。
答案 1 :(得分：0)
我已经通过使用上述@Ricardo提到的解决方案并通过使用Asynctask（Background Thread）将该解决方案与该解决方案组合来解决了此问题，因为它首先由于在Main UI Thread上调用Tasks.await（task）而给出了IllegalStateException。
因此，请使用： Aysnctask（背景线程）上的Tasks.await（任务）