title: firestore onSuccess listener isn't working
body: <p>I am trying to download some Quiz objects from my database.
  The following function is called from onCreate of a certain activity.</p>
  
  <pre><code> private void downloadQuizzesFromCloud(){
  
          String user_id = FirebaseAuth.getInstance().getCurrentUser().getUid();
          final FirebaseFirestore db = FirebaseFirestore.getInstance();
          String user_quizzes_path = "users/".concat(user_id).concat("/quizzes");
          Query userQuizzes = db.collection(user_quizzes_path);
  
          userQuizzes.get()
                  .addOnCompleteListener(new OnCompleteListener&lt;QuerySnapshot&gt;() {
                      @Override
                      public void onComplete(@NonNull Task&lt;QuerySnapshot&gt; task) {
                          if (task.isSuccessful()) {
                              quizzes.clear();
                              for (QueryDocumentSnapshot document : task.getResult()) {
  
                                  Quiz quizDownloaded = getQuizFromCloud(document.getId());
                                  quizzes.add(quizDownloaded);
                              }
                              Toast.makeText(QuizzesActivity.this,"downloaded to list ".concat(String.valueOf(quizzes.size()).concat("  quizzes")), Toast.LENGTH_SHORT).show();
                              //TODO put in recycle adapter
                          } else { }
                      }
                  });
  
      }
  </code></pre>
  
  <p>(user_quizzes_path contains the correct path to a collection of Quiz objects stored on the cloud)</p>
  
  <p>I debugged this functions and found out that after the command: </p>
  
  <pre><code> userQuizzes.get()
              .addOnCompleteListener(new OnCompleteListener&lt;QuerySnapshot&gt;()
  </code></pre>
  
  <p>The function finishes execution, that is the onComplete cases aren't checked and executed and all this code is just skipped.</p>
  
  <p>I tried to find this on the documentation of firebase but didn't find anything.
  Why is this happening and how can I fix this?</p>
  
  <p>Would appreciate some help here, thanks!</p>