How can I prevent asynchronous setState calls after widget disposal during Firebase sign-out?

The error occurs because your asynchronous code (the async for loop on your Firestore snapshots) continues running after the widget is disposed. When you call setState() (or any context‐based API) after the widget is unmounted (for example, when a user signs out or navigates back), you get that error.

Two common solutions are:

1. Check if Mounted Before setState
   Before calling setState(), check if the widget is still mounted. For example:

   DARTCopied
   if (!mounted) return;
   setState(() {
     items = tempList;
     isLoaded = true;
   });

   However, if your async loop is long running or continuously listening to a stream, checking mounted inside the loop might not be enough.

2. Cancel the Firestore Subscription on Dispose
   Rather than using an async for loop on your snapshots, you can use a StreamSubscription, which you cancel in the widget’s dispose() method. This way, the listener stops when the widget is removed from the tree.

   For example:

   DARTCopied
   class _ClientStoresPageState extends State<ClientStoresPage> {
     late List<Map<String, dynamic>> items;
     bool isLoaded = false;
     StreamSubscription? _subscription;
   
     @override
     void initState() {
       super.initState();
       getStoresSubscribed();
     }
   
     Future<void> getStoresSubscribed() async {
       try {
         if (idCurrentSession != "" && usrClient == true) {
           List<Map<String, dynamic>> tempList = [];
   
           // Listen to the collection stream.
           _subscription = FirebaseFirestore.instance
               .collection("ClientStores")
               .snapshots()
               .listen((storeSubscribedSnap) async {
             // Process each snapshot; note that if you have additional async calls,
             // you must be careful while using setState.
             for (var storeSubscribedDoc in storeSubscribedSnap.docs) {
               if (storeSubscribedDoc["StoreID"] != null) {
                 String idStore = storeSubscribedDoc["StoreID"];
                 var collection2 = FirebaseFirestore.instance
                     .collection("ClientStores")
                     .doc(idStore)
                     .collection("Clients");
                 
                 var docSnapshot = await collection2.doc(idCurrentSession).get();
                 if (docSnapshot.exists) {
                   Map<String, dynamic>? data = docSnapshot.data();
                   String clientIdStore = data?['StoreID'];
                   var dataStore = await FirebaseFirestore.instance
                       .collection("Stores")
                       .where("StoreID", isEqualTo: clientIdStore)
                       .get();
   
                   for (var element in dataStore.docs) {
                     tempList.add(element.data());
                   }
                   if (!mounted) return;
                   setState(() {
                     items = tempList;
                     isLoaded = true;
                   });
                 }
               }
             }
           });
         }
       } catch (e) {
         if (!mounted) return;
         ScaffoldMessenger.of(context).showSnackBar(SnackBar(
           backgroundColor: Colors.orangeAccent,
           content: Text(
             "$e",
             style: const TextStyle(fontSize: 18.0),
           ),
         ));
       }
     }
   
     @override
     void dispose() {
       // Cancel the subscription here to stop receiving snapshots.
       _subscription?.cancel();
       super.dispose();
     }
   
     @override
     Widget build(BuildContext context) {
       // Your ListView build code here
       return Scaffold(
         appBar: AppBar(
           leading: BackButton(
             onPressed: () => Navigator.of(context).pop(),
           ),
         ),
         body: isLoaded
             ? ListView.builder(
                 itemCount: items.length,
                 itemBuilder: (context, index) {
                   return ListTile(
                     title: Text(items[index]['StoreName'] ?? 'No Name'),
                   );
                 },
               )
             : const Center(child: CircularProgressIndicator()),
       );
     }
   }

In this revised code, the Firestore snapshots are listened to as a stream, and the subscription is stored in _subscription. In the dispose() method, we cancel that subscription so that no further async callbacks (and thus setState calls) occur after the widget is unmounted.

Using these approaches will ensure that when you navigate away or sign out, you won’t attempt to update a widget that no longer exists.