Flutter StreamSubscription not stopping or pausing

Question

In my Flutter app StreamSubscription is not pausing or cancelling. When I call cancel() if it started before, it will stop. If I call cancel() after starting, it will not stop. I am using Firestore snapshot listener. Below is my code. I have tried different methods but it's still not working. The problem is that the Firestore listener is not stopping after loading data.

    StreamSubscription<QuerySnapshot> streamSubscription;

    @override
    void initState() {
    super.initState();
    
        print("Creating a streamSubscription...");
        streamSubscription =Firestore.collection("name").document("d1").collection("d1")
            .snapshots().listen((data){
                //It will display items
            }, onDone: () { // Not excecuting
                print("Task Done");
            }, onError: (error) {
                print("Some Error");
        });
         streamSubscription.cancel(); //It will work but cancel stream before loading
    }

    @override
    void dispose() {
     streamSubscription.cancel(); //Not working
    super.dispose();
    }

Solution 1

When you push a new page, the previous page is still rendered and therefore dispose() is not called.

• How to get current route path in Flutter?

Also sometimes it can happen that the widget is not rendered anymore but dispose was not yet called, which can lead to weird error messages. So adding such a check is probably a good idea as well if you use dispose.

• https://docs.flutter.io/flutter/widgets/State/mounted.html

Change

//It will display items

to

if(myIsCurrentRoute && mounted) {
  //It will display items
}

Solution 2

You are not assigning the subscription into the right variable.

StreamSubscription<QuerySnapshot> subscription;

@override
void initState() {
super.initState();

    print("Creating a streamSubscription...");
    subscription=Firestore.collection("name").document("d1").collection("d1")
        .snapshots().listen((data){
            //It will display items
        }, onDone: () { // Not excecuting
            print("Task Done");
        }, onError: (error) {
            print("Some Error");
    });


     subscription.cancel(); //It will work but cancel stream before loading



}

@override
void dispose() {
 subscription.cancel(); //Not working
super.dispose();
}

Solution 3

I was experiencing the same problem and it turns out that the stream seems to keep listening for events for a while before canceling, but if you debug you will see that after dispose is called it will stop listening at some point. Therefore, Gunter's solution works fine, since you can prevent your callback function from being called if mount is false, which means your page is no longer there.