您的监听器类型为
StreamSubscription，因此您可以在监听器上调用一些有用的方法，例如
cancel()
CollectionReference reference = Firestore.instance.collection('Events');StreamSubscription<QuerySnapshot> streamSub = reference.snapshots().listen((querySnapshot) { querySnapshot.documentChanges.forEach((change) { // Do something with change });});//somewherestreamSub.cancel();
