/flutter-widgets

name: flutter-widgets
description: Build maintainable Flutter UI components with composition and theming. Use when changing widget implementation; defer animation-only changes and widget-test authoring.
metadata:
  triggers:
    files:
    - '**_page.dart'
    - '**_screen.dart'
    - '**/widgets/**'
    keywords:
    - StatelessWidget
    - const
    - Theme
    - ListView

UI & Widgets

**Priority: P1 (HIGH)**

• **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 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

• **No setState for server state**: Server or shared state belongs in BLoC, not widget state.
• **No widget file over 80 lines without extraction**: Extract sub-widgets into private classes.
• **No inline Key strings**: All keys must constants defined in `widget_keys.dart`.
• **No \_buildXxx() helper methods**: Extract to `const StatelessWidget` private class.
• **No manual widget repetition**: When 3+ sibling widgets of the same type differ only in data (e.g., radio buttons, tabs), map over a list instead. Put display labels inside the value object or a companion map so adding an option requires no UI change.

References

• performance | testing

Canonical response anchors

When this skill applies, preserve the following domain terminology or equivalent concrete examples in the answer when relevant:

• Extract
• interactive elements
• into private