Fix: setState() called after dispose()

setState() called after dispose(): _MyWidgetState#12345

This error means you're calling setState() on a widget that's already been removed from the widget tree. It's a lifecycle timing issue, and it's very common with async operations.

Why It Happens

When a widget is disposed (user navigated away, parent rebuilt without it), the State object is marked as unmounted. But if you have a pending Future, Stream, or Timer, its callback will still fire — and call setState() on a dead widget.

Fix 1: Check mounted Before setState

The simplest fix:

Future<void> _loadData() async {
  final result = await api.fetchData();
  if (!mounted) return;  // Widget was disposed during the await
  setState(() {
    _data = result;
  });
}

Fix 2: Cancel Subscriptions in dispose()

For streams and timers:

class _MyWidgetState extends State<MyWidget> {
  StreamSubscription? _subscription;
  Timer? _timer;
 
  @override
  void initState() {
    super.initState();
    _subscription = stream.listen((data) {
      setState(() => _items = data);
    });
    _timer = Timer.periodic(Duration(seconds: 5), (_) {
      setState(() => _counter++);
    });
  }
 
  @override
  void dispose() {
    _subscription?.cancel();
    _timer?.cancel();
    super.dispose();
  }
}

Fix 3: Use a Cancelable Completer

For complex async chains:

class _MyWidgetState extends State<MyWidget> {
  CancelableOperation<Data>? _operation;
 
  void _fetchData() {
    _operation?.cancel();
    _operation = CancelableOperation.fromFuture(
      api.fetchData(),
    );
    _operation!.value.then((data) {
      if (mounted) setState(() => _data = data);
    });
  }
 
  @override
  void dispose() {
    _operation?.cancel();
    super.dispose();
  }
}

InkPal Auto-Fix

InkPal detects this pattern and adds the mounted guard automatically:

inkpal.self_heal()
// Detects: setState after dispose pattern
// Fix: Adds mounted check before every setState in async context

Prevention Rules

1. Every await in a State method needs a mounted check after it
2. Every StreamSubscription needs cancellation in dispose()
3. Every Timer needs cancellation in dispose()
4. Consider using StatefulWidget alternatives (Riverpod, BLoC) that handle this automatically

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