flutter-frontend-design（Flutter frontend 设计）

Flutter Frontend Design Skill

This skill guides creation of distinctive, production-grade Flutter interfaces that avoid generic "AI slop" aesthetics. Implement real working Flutter/Dart code with exceptional attention to aesthetic details and creative choices.

The user provides Flutter UI requirements: a screen, widget, component, or full app to build. They may include context about the purpose, audience, platform targets, or technical constraints.

Design Thinking (Before Coding)

Before writing any Dart code, understand the context and commit to a BOLD aesthetic direction:

• Purpose: What problem does this interface solve? Who uses it? Mobile-first? Tablet? Web?
• Tone: Pick a strong direction: brutally minimal, maximalist chaos, retro-futuristic, organic/natural, luxury/refined, playful/toy-like, editorial/magazine, brutalist/raw, art deco/geometric, soft/pastel, industrial/utilitarian, glassmorphism, neumorphism, claymorphism, etc.
• Platform: Material 3, Cupertino, or custom design system? Adaptive UI?
• Constraints: State management (Riverpod, Bloc, Provider, GetX), navigation (GoRouter, auto_route), target platforms.
• Differentiation: What makes this UNFORGETTABLE? What's the one thing someone will remember?

CRITICAL: Choose a clear conceptual direction and execute it with precision. Bold maximalism and refined minimalism both work — the key is intentionality, not intensity.

Flutter Architecture Patterns

Always follow these Flutter-specific patterns:

Widget Structure

lib/
├── main.dart
├── app.dart                    # MaterialApp / CupertinoApp config
├── core/
│   ├── theme/
│   │   ├── app_theme.dart      # ThemeData definitions
│   │   ├── app_colors.dart     # Color constants & extensions
│   │   ├── app_typography.dart # TextStyle definitions
│   │   └── app_spacing.dart    # Spacing constants
│   ├── constants/
│   └── utils/
├── features/
│   └── feature_name/
│       ├── presentation/
│       │   ├── screens/
│       │   ├── widgets/
│       │   └── controllers/
│       ├── domain/
│       └── data/
└── shared/
    └── widgets/                # Reusable custom widgets

State Management

• Use StatefulWidget for simple local state
• Recommend Riverpod or Bloc for complex state
• Always separate UI from business logic
• Use ValueNotifier / ChangeNotifier for lightweight reactive patterns

Responsive Design

// Always think responsive
LayoutBuilder(
  builder: (context, constraints) {
    if (constraints.maxWidth > 1200) return _desktopLayout();
    if (constraints.maxWidth > 600) return _tabletLayout();
    return _mobileLayout();
  },
)

Flutter Aesthetics Guidelines

Typography

• NEVER use default Material font (Roboto) without customization
• Use Google Fonts package (google_fonts) for distinctive typography
• Pair a bold display font with a refined body font
• Examples of strong pairings:

- Display: Playfair Display / Body: Source Sans Pro - Display: Space Grotesk / Body: DM Sans - Display: Cormorant Garamond / Body: Fira Sans - Display: Sora / Body: Inter (when Inter fits the design) - Display: Clash Display / Body: Satoshi

• Define ALL text styles in AppTypography class using TextTheme extensions

Color & Theme

• Define colors using ColorScheme.fromSeed() or custom ColorScheme
• Use ThemeExtension<T> for custom color properties beyond Material
• Support BOTH light and dark themes from the start
• CSS variables equivalent → Dart constants + Theme.of(context).extension<T>()
• Dominant colors with sharp accents outperform timid, evenly-distributed palettes

// Example: Strong color system
class AppColors {
  // Primary palette
  static const primary = Color(0xFF1A1A2E);
  static const accent = Color(0xFFE94560);
  static const surface = Color(0xFF16213E);
  static const background = Color(0xFF0F3460);

  // Semantic colors
  static const success = Color(0xFF00C897);
  static const warning = Color(0xFFFFB800);
  static const error = Color(0xFFFF4757);

  // Gradients
  static const heroGradient = LinearGradient(
    colors: [Color(0xFF667eea), Color(0xFF764ba2)],
    begin: Alignment.topLeft,
    end: Alignment.bottomRight,
  );
}

Motion & Animation

Flutter excels at animation. Use it:

• Implicit animations: AnimatedContainer, AnimatedOpacity, AnimatedScale, AnimatedSlide, AnimatedSwitcher
• Hero animations: For screen transitions with shared elements
• Staggered animations: Use Interval with AnimationController for orchestrated reveals
• Micro-interactions: GestureDetector + AnimatedScale for tap feedback
• Page transitions: Custom PageRouteBuilder with SlideTransition, FadeTransition, ScaleTransition
• Lottie: For complex illustrations and loading states (lottie package)
• Rive: For interactive vector animations (rive package)

// Staggered list animation example
class StaggeredListItem extends StatelessWidget {
  final int index;
  final Animation<double> animation;

  Widget build(BuildContext context) {
    return SlideTransition(
      position: Tween<Offset>(
        begin: const Offset(0, 0.3),
        end: Offset.zero,
      ).animate(CurvedAnimation(
        parent: animation,
        curve: Interval(
          index * 0.1,
          (index * 0.1) + 0.4,
          curve: Curves.easeOutCubic,
        ),
      )),
      child: FadeTransition(
        opacity: animation,
        child: child,
      ),
    );
  }
}

Spatial Composition

• Use SliverAppBar with FlexibleSpaceBar for immersive scroll effects
• CustomScrollView with mixed Sliver widgets for complex layouts
• Stack + Positioned for overlapping elements
• Transform for rotation, skew, perspective effects
• ClipPath / CustomClipper for non-rectangular shapes
• CustomPaint / CustomPainter for unique backgrounds and decorative elements

Backgrounds & Visual Details

• ShaderMask for gradient text and masked effects
• BackdropFilter with ImageFilter.blur for glassmorphism
• CustomPainter for geometric patterns, noise textures, decorative elements
• DecoratedBox with complex BoxDecoration (gradients, shadows, borders)
• Container with BoxShadow lists for layered depth effects
• Use dart:ui canvas operations for grain overlays and mesh gradients

// Glassmorphism card
ClipRRect(
  borderRadius: BorderRadius.circular(20),
  child: BackdropFilter(
    filter: ImageFilter.blur(sigmaX: 15, sigmaY: 15),
    child: Container(
      decoration: BoxDecoration(
        color: Colors.white.withOpacity(0.1),
        borderRadius: BorderRadius.circular(20),
        border: Border.all(color: Colors.white.withOpacity(0.2)),
      ),
      child: content,
    ),
  ),
)

What to NEVER Do

• NEVER use default Material theme without customization
• NEVER use only Scaffold + ListView + Card with zero styling
• NEVER rely solely on Material default colors (purple/teal)
• NEVER ignore dark mode support
• NEVER skip animations entirely — Flutter's animation system is its superpower
• NEVER hardcode sizes — use MediaQuery, LayoutBuilder, Flexible, Expanded
• NEVER use generic placeholder patterns that look like every other Flutter tutorial
• NEVER ignore platform conventions (iOS users expect Cupertino patterns)

Package Recommendations

Delivery Format

When building Flutter UI:

1. Single widget/screen: Provide complete .dart file with imports
2. Multi-screen feature: Provide folder structure + all files
3. Full app: Provide pubspec.yaml + complete lib/ structure
4. Always include pubspec.yaml dependencies when using external packages
5. Code must compile and run — no pseudo-code or incomplete snippets
6. Include comments explaining non-obvious design decisions

Quality Checklist

Before delivering Flutter UI code, verify:

• Custom ThemeData with unique colors and typography
• Responsive layout (mobile + tablet minimum)
• At least 2-3 meaningful animations or transitions
• Dark mode support or explicit dark/light theme
• Proper widget extraction (no mega-build methods)
• Performance considerations (const constructors, RepaintBoundary where needed)
• Accessibility (Semantics widgets, sufficient contrast ratios)
• Platform-adaptive elements where appropriate

Remember: Flutter gives you a pixel-perfect canvas with 120fps animations. Don't hold back — show what can truly be created when committing fully to a distinctive vision.