Bug Solving Skill (Flutter)
Foundation: Extends shared-bug-investigation with Flutter patterns.
Flutter Context
flutter --version && grep "sdk:" pubspec.yaml
grep -r "BlocProvider\|ChangeNotifier\|GetX" lib/ # State management
RCA: Check All Layers (data/domain/view)
# View Layer: Bloc/Cubit, widgets, state
find lib/feature/<feature>/view -name "*.dart"
# Domain Layer: Models, repository interfaces, business logic
find lib/feature/<feature>/domain -name "*.dart"
# Data Layer: DTOs, datasources, API calls
find lib/feature/<feature>/data -name "*.dart"
Debug by layer: View (Bloc emits?) → Domain (model mapping?) → Data (DTO parsing?)
Common Bug Patterns
Bloc State
// ❌ Missing emit → ✅ Add emit(LoadingState()), emit(LoadedState(data)), emit(ErrorState())
Null Safety
// ❌ user!.name → ✅ user?.name ?? 'Guest'
BuildContext After Async
// ❌ Navigator.pop(context) after await → ✅ if (!mounted) return; Navigator.pop(context);
GetIt DI
// ❌ Not registered → ✅ Add @injectable, run build_runner
Method Channels
// ❌ Wrong name → ✅ Match iOS/Android channel name
Widget Rebuilds
// ❌ BlocBuilder wraps Scaffold → ✅ Wrap only body
Memory Leaks
// ❌ Stream not closed → ✅ Override close(), call super.close()
Error Quick Reference
| Error | Fix |
|---|---|
type 'Null' is not a subtype |
Add ?? defaults |
Looking up deactivated widget |
Check mounted |
Object not registered |
Add @injectable, run build_runner |
MissingPluginException |
Implement native iOS/Android |
setState() after dispose() |
Cancel timers/streams |
RenderBox overflow |
Fix constraints |
Tools
flutter analyze # Must pass (0 errors)
flutter test # All tests
flutter run --profile # Performance
Validation
-
flutter analyze= 0 errors -
flutter testpasses - Manual test fixed
- Tested iOS + Android (if platform-specific)
Source: Desquared/agents-rules-skills — distributed by TomeVault.