Flutter Widgets

UI & Widgets

Priority: P1 (OPERATIONAL)

Standards for building reusable, performant Flutter widgets and UI components.

• State: Use StatelessWidget by default. StatefulWidget only for local state/controllers.
• Composition: Extract UI into small, atomic const widgets.
• Theming: Use Theme.of(context). No hardcoded colors.
• Layout: Use Flex + Gap/SizedBox.
• Widget Keys: All interactive elements must use keys from widget_keys.dart.
• File Size: If a UI file exceeds ~80 lines, extract sub-widgets into private classes.
• Specialized:
  • SelectionArea: For multi-widget text selection.
  • InteractiveViewer: For zoom/pan.
  • ListWheelScrollView: For pickers.
  • IntrinsicWidth/Height: Avoid unless strictly required.
• Large Lists: Always use ListView.builder.

class AppButton extends StatelessWidget {
  final String label;
  final VoidCallback onPressed;
  const AppButton({super.key, required this.label, required this.onPressed});

  @override
  Widget build(BuildContext context) => ElevatedButton(onPressed: onPressed, child: Text(label));
}

Anti-Patterns

• ❌ setState(() { _orders = await repo.fetch(); }) — server/shared state belongs in a BLoC, not widget state
• ❌ Widget file over 80 lines without extracting private sub-widget classes — helper methods returning Widget are not a substitute
• ❌ Key('submit-button') inline in widget code — all keys must be constants defined in widget_keys.dart
• ❌ Widget _buildHeader() { … } helper methods — extract to a const StatelessWidget private class for proper rebuilding control

Related Topics

performance | testing