Java/Firestore – 在循环至下一项之前等待数据被读取（异步）

huangapple
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英文:

Java/Firestore - Wait for data to be read before looping to next item (Async)

问题

我正在尝试在我的项目中实现一个VMMV架构，以便在对象之间实现低耦合。

我的Firestore数据库中有两个实体：Offers（优惠）和Users（用户）。

每个优惠都是由一个用户发布的。

在检索到所有优惠后，我想将有关用户的信息（姓名、个人头像、描述）添加到OffersViewModel（以便将其绑定到我拥有的RecicleView）。

问题是，在将优惠传递给外部层之前，我无法同步读取用户配置文件信息（以便可以将它们绑定在一个模型中）。

以下是我拥有的内容：

  1. // 代码部分已略去

我在YT上找到了一个教程，解释了我应该如何从回调中检索数据，但似乎不起作用（或者我实现得不好）。

我已经尝试过一些调试方法，比如使用日志记录，对回调进行封装，执行顺序如下：

1- 循环之前 -> 列表未更改
2- 循环内 -> 列表未更改
3- 循环之后 -> 列表未更改
4- 在回调内 -> 列表已更改

对于这个问题，我非常感谢任何帮助！

英文:

I am trying to implement a VMMV architecture on my project in order to have low coupling between objects.

I have 2 entities in my Firestore database: Offers and Users.

Each offer is posted by a user.

After retrieving all offers, I want to add information about the user (name, profileImage, description) to the OffersViewModel (to bind it to the RecicleView I have).

The problem is I cannot sync the reading of user profile information before the offers are being passed to the outer layers(so I can bind them in 1 model)

Here is what I have:

  1. package com.kaju.activities.workingActivity.Repository;
  3. import android.util.Log;
  5. import androidx.annotation.NonNull;
  7. import com.google.android.gms.tasks.OnCompleteListener;
  8. import com.google.android.gms.tasks.Task;
  9. import com.google.firebase.firestore.CollectionReference;
  10. import com.google.firebase.firestore.DocumentReference;
  11. import com.google.firebase.firestore.DocumentSnapshot;
  12. import com.google.firebase.firestore.FirebaseFirestore;
  13. import com.google.firebase.firestore.Query;
  14. import com.google.firebase.firestore.QuerySnapshot;
  15. import com.kaju.activities.workingActivity.Model.ProviderOfferModel;
  16. import com.kaju.activities.workingActivity.Model.ProviderProfileModel;
  18. import java.util.List;
  20. public class FirestoreOfferRepository {
  21.     //We get the currently linked firebase firestore database
  22.     private FirebaseFirestore firebaseFirestore = FirebaseFirestore.getInstance();
  23.     private CollectionReference offersReference = firebaseFirestore.collection("offers");
  24.     private OnFirestoreTaskComplete onFirestoreTaskComplete;
  28.     public  FirestoreOfferRepository(OnFirestoreTaskComplete onFirestoreTaskComplete){
  29.         this.onFirestoreTaskComplete = onFirestoreTaskComplete;
  30.     }
  32.     public void getOffersData(final String annoucementID){
  33.         Query offersForAnnoucement = offersReference.whereEqualTo("announcementID", annoucementID);
  35.         offersForAnnoucement.get().addOnCompleteListener(new OnCompleteListener<QuerySnapshot>() {
  36.             @Override
  37.             public void onComplete(@NonNull Task<QuerySnapshot> task) {
  38.                 if(task.isSuccessful()){
  39.                     final List<ProviderOfferModel> newOffers = task.getResult().toObjects(ProviderOfferModel.class);
  40.                     
  41.                     //We try to get the information for each user
  42.                     for(final ProviderOfferModel currentOffer : newOffers){
  43.                         String userID = currentOffer.getUserID();
  44.                         getUserProfileData(new UserDataCallback() {
  45.                             @Override
  46.                             public void userReadDataCallback(ProviderProfileModel currentUser) {
  47.                                 int index = newOffers.indexOf(currentOffer);
  48.                                 newOffers.get(index).setProvider(currentUser);
  49.                                  //This part here is executed only after the loop is over 
  50.                             }
  51.                         }, userID);
  53.                     }
  54.                      //@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
  55.                      // I want to wait here so the above callBacks are finished
  57.                      //And we send the data to the outside layers
  58.                     onFirestoreTaskComplete.offerDataAdded(newOffers);
  59.                 }else{
  60.                     onFirestoreTaskComplete.onError(task.getException());
  61.                 }
  62.             }
  63.         });
  64.     }  
  65.         
  67.     public void getUserProfileData(final UserDataCallback userDataCallback, String userID)
  68.     {
  69.         firebaseFirestore.collection("users").document(userID).get()
  70.                 .addOnCompleteListener(new OnCompleteListener<DocumentSnapshot>() {
  71.                     @Override
  72.                     public void onComplete(@NonNull Task<DocumentSnapshot> task) {
  73.                         if(task.isSuccessful()) {
  74.                             ProviderProfileModel currentUser = task.getResult().toObject(ProviderProfileModel.class);
  75.                             userDataCallback.userReadDataCallback(currentUser);
  76.                         }
  78.                     }
  79.                 });
  80.     }
  83.     public interface OnFirestoreTaskComplete{
  84.         void offerDataAdded(List<ProviderOfferModel> offerRepositoryData);
  85.         void onError(Exception e);
  86.     }
  88.     public interface UserDataCallback{
  89.         void userReadDataCallback(ProviderProfileModel currentUser);
  90.     }
  92.    
  96. }

I found a tutorial on YT which explains how I should retrieve the data from the callback but it doesn't seem to work(or I implemented it badly).

I have tried some debugging with Logs, surrounding the callback, and the order of executing is like this:

1-Before loop -> List unchanged

2-In loop -> List unchanged

3-After loop -> List unchanged

4-In callBack -> List changed

I appreciate any help on the matter !

答案1

得分: 1

以下是翻译好的内容：

这样，我最终做的方式是这样的：

  1. public void getOffersData(final String annoucementID){
  2.     Query offersForAnnoucement = offersReference.whereEqualTo("announcementID", annoucementID);
  4.     offersForAnnoucement.get().addOnCompleteListener(new OnCompleteListener<QuerySnapshot>() {
  5.         @Override
  6.         public void onComplete(@NonNull Task<QuerySnapshot> task) {
  7.             if(task.isSuccessful()){
  8.                 final List<ProviderOfferModel> newOffers = task.getResult().toObjects(ProviderOfferModel.class);
  10.                 // 我们尝试获取每个用户的信息
  11.                 for(final ProviderOfferModel currentOffer : newOffers){
  12.                     String userID = currentOffer.getUserID();
  13.                     getUserProfileData(new UserDataCallback() {
  14.                         @Override
  15.                         public void userReadDataCallback(ProviderProfileModel currentUser) {
  16.                             int index = newOffers.indexOf(currentOffer);
  17.                             newOffers.get(index).setProvider(currentUser);
  18.                             onFirestoreTaskComplete.offerDataAdded(newOffers);
  19.                         }
  20.                     }, userID);
  22.                 }
  23.                  // 然后我们将数据发送给外部层
  24.             }else{
  25.                 onFirestoreTaskComplete.onError(task.getException());
  26.             }
  27.         }
  28.     });
  29. }

基本上，每当我为1个以上的用户检索数据时，我都会将包含用户信息的新更新列表发送到ViewModel和LiveData（发送到外部层）。

它能工作，我认为这是因为LiveData的监听器onChanged会在新信息写入时更新适配器。

即使它能工作，我认为这还有点不够完善。我会欣赏其他获得这个（预期）结果的方法。

英文:

So the way I did it after all is like this:

  1. public void getOffersData(final String annoucementID){
  2.     Query offersForAnnoucement = offersReference.whereEqualTo(&quot;announcementID&quot;, annoucementID);
  4.     offersForAnnoucement.get().addOnCompleteListener(new OnCompleteListener&lt;QuerySnapshot&gt;() {
  5.         @Override
  6.         public void onComplete(@NonNull Task&lt;QuerySnapshot&gt; task) {
  7.             if(task.isSuccessful()){
  8.                 final List&lt;ProviderOfferModel&gt; newOffers = task.getResult().toObjects(ProviderOfferModel.class);
  10.                 //We try to get the information for each user
  11.                 for(final ProviderOfferModel currentOffer : newOffers){
  12.                     String userID = currentOffer.getUserID();
  13.                     getUserProfileData(new UserDataCallback() {
  14.                         @Override
  15.                         public void userReadDataCallback(ProviderProfileModel currentUser) {
  16.                             int index = newOffers.indexOf(currentOffer);
  17.                             newOffers.get(index).setProvider(currentUser);
  18.                             onFirestoreTaskComplete.offerDataAdded(newOffers);
  19.                         }
  20.                     }, userID);
  22.                 }
  23.                  //And we send the data to the outside layers
  24.             }else{
  25.                 onFirestoreTaskComplete.onError(task.getException());
  26.             }
  27.         }
  28.     });
  29. }

Basically, every time I retrieve data for 1 more user, I send the newly updated list with the user information to the ViewModel and to LiveData (to the outside layer).

It works and I think it does because of the LiveData listener onChanged which updates the Adapter everytime new information is written.

Even if it works, I think is a bit sketchy. I would appreciate any other way to obtain this (expected) result

huangapple
  • 本文由 发表于 2020年8月21日 01:53:45
  • 转载请务必保留本文链接：https://go.coder-hub.com/63510722.html
  • android
  • asynchronous
  • callback
  • google-cloud-firestore
  • java
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