Kotlin - 如何使用onCompleteListener从Firestore获取数据？(Kotlin - How to do onCompleteListener to get data From Firestore?)

 我有问题从Firestore获取数据，在JavaCode中我们可以这样做： 
 
 
 
 
 
  
DocumentReference docRef = db.collection("cities").document("SF");
docRef.get().addOnCompleteListener(new OnCompleteListener<DocumentSnapshot>() {
    @Override
    public void onComplete(@NonNull Task<DocumentSnapshot> task) {
        if (task.isSuccessful()) {
            DocumentSnapshot document = task.getResult();
            if (document != null) {
                Log.d(TAG, "DocumentSnapshot data: " + task.getResult().getData());
            } else {
                Log.d(TAG, "No such document");
            }
        } else {
            Log.d(TAG, "get failed with ", task.getException());
        }
    }
});
 
 
 
 
 
 但在Kotlin，当我尝试覆盖onComplete函数时，它不可用。 那么，我怎么能得到“任务”？ 

I have a problem to Get data From Firestore, in Java code we can do this :
 
 
 
 
 
  
DocumentReference docRef = db.collection("cities").document("SF");
docRef.get().addOnCompleteListener(new OnCompleteListener<DocumentSnapshot>() {
    @Override
    public void onComplete(@NonNull Task<DocumentSnapshot> task) {
        if (task.isSuccessful()) {
            DocumentSnapshot document = task.getResult();
            if (document != null) {
                Log.d(TAG, "DocumentSnapshot data: " + task.getResult().getData());
            } else {
                Log.d(TAG, "No such document");
            }
        } else {
            Log.d(TAG, "get failed with ", task.getException());
        }
    }
});
 
 
 
 
 
but in Kotlin, when I try to override the onComplete function, it's unavailable. so, how I can get the "task"?

原文：https://stackoverflow.com/questions/47214368