flutter-memory-leak

Flutter Memory Leak

Full reference: template.md

Key rules

Dispose everything in StatefulWidget

Every controller, subscription, and notifier created in initState or State fields must be disposed in dispose(). No exceptions.

class _MyPageState extends State<MyPage> {
  late final TextEditingController _text;
  late final AnimationController _anim;
  late final ScrollController _scroll;
  late final FocusNode _focus;
  StreamSubscription<dynamic>? _sub;

  @override
  void initState() {
    super.initState();
    _text   = TextEditingController();
    _anim   = AnimationController(vsync: this, duration: Durations.medium2);
    _scroll = ScrollController();
    _focus  = FocusNode();
    _sub    = someStream.listen(_onEvent);
  }

  @override
  void dispose() {
    _text.dispose();
    _anim.dispose();
    _scroll.dispose();
    _focus.dispose();
    _sub?.cancel();
    super.dispose();
  }
}

Cubits: cancel subscriptions in close()

class MyCubit extends BaseCubit<MyState> {
  MyCubit({...}) : super(const MyInitial());
  StreamSubscription<dynamic>? _sub;

  void init() {
    _sub = someStream.listen(_onEvent);
  }

  @override
  Future<void> close() {
    _sub?.cancel();
    return super.close();
  }
}

Never capture BuildContext across async gaps without mounted check

// DON'T
Future<void> _submit() async {
  await someAsyncOp();
  context.go('/next'); // context may be stale
}

// DO
Future<void> _submit() async {
  await someAsyncOp();
  if (!mounted) return;
  context.go('/next');
}

Enable leak_tracker globally

Add leak_tracker_flutter_testing: 3.0.9 to dev_dependencies, then create a global test config:

// test/flutter_test_config.dart — auto-loaded by test runner for ALL test files
import 'dart:async';
import 'package:leak_tracker_flutter_testing/leak_tracker_flutter_testing.dart';

Future<void> testExecutable(FutureOr<void> Function() testMain) async {
  LeakTesting.enable();
  await testMain();
}