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java - 为什么我的 else 块没有在 java android studio 的 OnClickListener 中执行

问题描述

我创建了一个功能，让我的应用程序用户最喜欢的商店。现在，如果用户已经收藏了一家商店并再次单击该按钮，它应该从 Firestore 数据库中删除该记录。

我的代码仅在与查询匹配并且任务成功时才有效，但不执行我else的部分代码。这是为什么？

query当和匹配时，下面的代码可以正常工作task is successful，但是当不匹配时，它不会执行该else部分。有谁知道为什么？

public void onClick(View view) {
        Task ref = fStore.collection("Favorites")
           .whereEqualTo("shopID", SID).whereEqualTo("usersID", UID)
                      .get()
          .addOnCompleteListener(new OnCompleteListener<QuerySnapshot>() {
                       @Override
     public void onComplete(@NonNull Task<QuerySnapshot> task) {
                    if (task.isSuccessful()) {
             for (QueryDocumentSnapshot document : task.getResult()) {
                              document.getReference().delete();
                                        }
                   } else {
      Map<String, Object> fav = new HashMap<>();
    
                         

         fav.put("shopID", SID);
         fav.put("usersID", UID);
         fav.put("ShopHeaderImg", sHI);
         fav.put("ShopProfileImg", sPI);
         fav.put("address", sA);
         fav.put("costEst", sCost);
         fav.put("country", sC);
         fav.put("latitude", sLat);
         fav.put("location", sL);
         fav.put("name", sN);
         fav.put("numTables", sNumTable);
         fav.put("ratings", sR);
         fav.put("summary", sSummary);
         fav.put("timing", sT);
    
    
                                      
      fStore.collection("Favorites").add(fav)
.addOnSuccessListener(new OnSuccessListener<DocumentReference>() {
                       @Override
     public void onSuccess(DocumentReference documentReference) {
                                                Toast.makeText(DetailsActivity.this, "Saved", Toast.LENGTH_SHORT).show();
     }).addOnFailureListener(new OnFailureListener() {
    public void onFailure(@NonNull Exception e) {
   Toast.makeText(DetailsActivity.this, "Something went wrong", Toast.LENGTH_SHORT).show();
                                            }
                                        });
                                    }
                                }
                          

  });

标签： javaandroidgoogle-cloud-firestore

解决方案

I think you are misunderstanding what task.isSuccessful() means. That method will return true if there were no errors during the execution of the query. A query that returns no documents isn't an error. That situation is perfectly normal, and considered successful. An error only happens when you try to execute a query that Firestore can't actually run.

If you want to check if a query returned no documents, you should look at the QuerySnapshot contained in the task results. It has a method isEmpty() that will tell you if there are documents.

public void onComplete(@NonNull Task<QuerySnapshot> task) {
    if (task.isSuccessful()) {
        QuerySnapshot querySnapshot = task.getResult();
        if (querySnapshot.isEmpty()) {
            // put code here to deal with no documents in the result
        }
        else {
            // put code here to deal with documents present in the result
            for (QueryDocumentSnapshot document : querySnapshot) {
            }
        }
    }
}

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