flutter

Flutter Cross-Platform UI AI Skill Guide

Overview & Engine Architecture

Flutter paints UI with a widget tree compiled to native ARM/x64 (and web/desktop targets). Everything is a widget; rebuilds are cheap when state is localized. Agents prefer composition over deep inheritance, choose an explicit state approach (Riverpod/Bloc/Provider) and stick to it, and keep platform-specific code behind clean facades.

Dart app
  -> Widget tree (build)
      -> Element / RenderObject
          -> Skia / Impeller
              -> iOS / Android / Web / Desktop

When to use this skill

• Building or refactoring Flutter screens
• Fixing unnecessary rebuilds and async UI races
• Adding platform views or method channels carefully
• Preparing release/signing build configs

Operational directives

1. Keep build() pure - no side effects; trigger work from callbacks/initState/providers.
2. Use const constructors where possible to cut rebuild cost.
3. Handle loading/error/empty states explicitly for every async boundary.
4. Do not block the UI isolate with heavy JSON/parse - use compute/isolates when needed.
5. Match Flutter/Dart SDK constraints in CI to local pubspec constraints.

Widget sketch

class ItemCount extends StatelessWidget {
  const ItemCount({super.key, required this.qty});
  final int qty;

  @override
  Widget build(BuildContext context) {
    return Text('Qty: $qty');
  }
}

class AddItemButton extends StatefulWidget {
  const AddItemButton({super.key, required this.onAdd});
  final Future<void> Function() onAdd;

  @override
  State<AddItemButton> createState() => _AddItemButtonState();
}

class _AddItemButtonState extends State<AddItemButton> {
  bool _busy = false;

  Future<void> _handle() async {
    if (_busy) return;
    setState(() => _busy = true);
    try {
      await widget.onAdd();
    } finally {
      if (mounted) setState(() => _busy = false);
    }
  }

  @override
  Widget build(BuildContext context) {
    return ElevatedButton(
      onPressed: _busy ? null : _handle,
      child: Text(_busy ? 'Saving...' : 'Add'),
    );
  }
}