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🎨 SmartLib Theme - Effortless Flutter Theme Management

A zero-boilerplate, BLoC-powered Flutter theme management library that makes it incredibly simple to create, switch, and customize themes—light, dark, or any style you dream of!

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🌟 Why Use This Library?

• ✅ One-time setup: Initialize once, then forget about theme plumbing.
• ✅ Custom themes made simple: Create themes with your brand colors in seconds.
• ✅ Dynamic switching: Switch themes anywhere in your app with a single line of code.
• ✅ Persistent themes: Themes stay saved across app restarts.
• ✅ Scalable: Supports dozens of themes without performance issues.

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Theming your Flutter project as Master

Based on a Medium article by Karo Hovhannisyan — one of the most skilled mobile architects in the industry — this library is perfect for apps that need flexible theming with zero complexity.

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📦 Built With

• Flutter (v3.7.2+)
• BLoC for state management
• SharedPreferences for persistence
• ThemeExtension for custom design tokens

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🚀 Quick Start Guide

0. TL;DR

Key Methods:

1. await AppThemeManager.init(themes: [])
2. Wrap MaterialApp with AppThemeBuilder(theme: theme)
3. AppThemeManager.changeTheme(context: context, themeKey: 'key')
4. AppThemeManager.getCurrentTheme(context: context) // Always returns the updated theme

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1. Install the Package

Add to pubspec.yaml:

dependencies:  
  smart_lib_theme: ^0.1.0  # Replace with latest version

Then run:

flutter pub get  

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2. Initialize the Theme Manager

In your main.dart, define supported themes:

import 'package:flutter/material.dart';  
import 'package:smart_lib_theme/core/theme/default/themes.dart';  
import 'package:smart_lib_theme/features/theme/presentation/app_theme_manager.dart';  
import 'package:smart_lib_theme/features/theme/presentation/widgets/app_theme_builder.dart';  

Future<void> main() async {  
  await AppThemeManager.init(themes: [  
    AppTheme(key: 'light', themeData: AppDefaultThemesData().light),  
    AppTheme(key: 'dark', themeData: AppDefaultThemesData().dark),  
  ]);  
  runApp(const MyApp());  
}  

✅ Replace AppDefaultThemesData() with your custom theme class (see below).

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3. Wrap Your App with AppThemeBuilder

Ensures dynamic theme updates across the entire UI:

class MyApp extends StatelessWidget {  
  const MyApp({super.key});  

  @override  
  Widget build(BuildContext context) {  
    return AppThemeBuilder(  
      builder: (theme) {  
        return MaterialApp(  
          title: 'Themed App',  
          theme: theme, // <-- Dynamic theme applied here  
          home: const HomePage(),  
        );  
      },  
    );  
  }  
}  

🧠 One-time setup: Done once, works forever.

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4. Switch Themes Dynamically

From any widget, change themes by passing the theme key:

GestureDetector(  
  onTap: () {  
    AppThemeManager.changeTheme(context: context, themeKey: 'dark');  
  },  
  child: Text('Switch to Dark Mode'),  
)  

🔄 The UI updates instantly thanks to BLoC and ThemeExtension.
⚠️ If the themeKey doesn’t exist, ThemeExceptionConstants.notFoundKey is thrown.

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5. Access Theme Colors & Styles

Use BuildContext extensions for colors and text styles:

Text(  
  'Styled Text',  
  style: context.textTheme().titleLarge?.copyWith(  
    color: context.appColors().onPrimary,  
  ),  
),  
Container(  
  color: context.appColors().surface,  
  child: Text('Surface Background'),  
),  

🎨 All tokens (colors, shapes, text styles) are available via context.appColors() and context.textTheme().

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🎨 Create Custom Themes

1. Define Your Own Colors

Extend AppThemeExtension to define your brand palette:

class MyCustomThemeExtension extends AppThemeExtension {  
  MyCustomThemeExtension()  
      : super(  
          primary: Colors.purple,  
          onPrimary: Colors.white,  
          secondary: Colors.tealAccent,  
          onSecondary: Colors.black,  
          // Override other tokens as needed  
        );  
}  

2. Use Custom Themes in Initialization

Replace defaults with your custom themes:

await AppThemeManager.init(themes: [  
  AppTheme(key: 'custom', themeData: ThemeData(  
    extensions: [MyCustomThemeExtension()],  
    colorScheme: ColorScheme.fromSeed(seedColor: Colors.purple),  
  )),  
]);  

🎯 Now use AppThemeManager.changeTheme(context, themeKey: 'custom') to switch to your theme!

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🧪 Example: Theme Switcher UI

class HomePage extends StatelessWidget {  
  const HomePage({super.key});  

  @override  
  Widget build(BuildContext context) {  
    return Scaffold(  
      backgroundColor: context.appColors().surface,  
      body: Column(  
        children: [  
          const SizedBox(height: 300),  
          Center(  
            child: GestureDetector(  
              onTap: () => AppThemeManager.changeTheme(context: context, themeKey: 'light'),  
              child: Text('Light Theme'),  
            ),  
          ),  
          const SizedBox(height: 100),  
          Center(  
            child: GestureDetector(  
              onTap: () => AppThemeManager.changeTheme(context: context, themeKey: 'dark'),  
              child: Text('Dark Theme', style: context.textTheme().bodyMedium),  
            ),  
          ),  
        ],  
      ),  
    );  
  }  
}  

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📦 Folder Structure (Clean Architecture)

lib/  
├── core/                 # Shared utilities (ThemeExtension, default themes)  
│   └── theme/  
│       ├── default/      # Default light/dark themes  
│       ├── extensions/   # ThemeExtension definitions  
│       └── data/         # Component-specific styling (buttons, text, etc.)  
├── features/  
│   └── theme/  
│       ├── domain/       # Entities, use cases  
│       ├── data/         # Repository + SharedPreferences impl  
│       └── presentation/ # BLoC, widgets, manager  
└── di/                   # Dependency injection  

📄 License

MIT License – see LICENSE for details.

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🤝 Contributing

Feel free to open issues or PRs! See CONTRIBUTING.md for guidelines.

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📬 Feedback

Have questions or suggestions? Reach out on GitHub or email me at dallakyanvanik@gmail.com.

✨ Maintained by Vanik Dallakyan

Made with ❤️ for Flutter developers everywhere.

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