# Flutter — Google Cross-Platform UI Toolkit for Beautiful Apps

> Flutter is Google cross-platform UI toolkit for crafting beautiful, natively compiled applications for mobile, web, desktop, and embedded devices from a single codebase. Powered by the Dart language and the Skia rendering engine (now Impeller).

## Install

Save as a script file and run:

## Quick Use

```bash
# Install via FVM (Flutter Version Manager, recommended)
brew tap leoafarias/fvm
brew install fvm
fvm install stable
fvm use stable

# Or download SDK directly
# https://docs.flutter.dev/get-started/install

flutter doctor
flutter create my_app
cd my_app
flutter run                  # Picks connected device
flutter run -d chrome        # Web
flutter run -d macos         # Desktop
```

A minimal widget:
```dart
import "package:flutter/material.dart";

void main() => runApp(const TokRepoApp());

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

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: "TokRepo",
      theme: ThemeData(colorSchemeSeed: Colors.blue, useMaterial3: true),
      home: const CounterPage(),
    );
  }
}

class CounterPage extends StatefulWidget {
  const CounterPage({super.key});
  @override
  State<CounterPage> createState() => _CounterState();
}

class _CounterState extends State<CounterPage> {
  int count = 0;
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: const Text("Counter")),
      body: Center(child: Text("Count: $count", style: const TextStyle(fontSize: 32))),
      floatingActionButton: FloatingActionButton(
        onPressed: () => setState(() => count++),
        child: const Icon(Icons.add),
      ),
    );
  }
}
```

## Intro

Flutter is Google open-source UI toolkit for building beautiful, natively compiled applications for mobile, web, desktop, and embedded devices from a single Dart codebase. First released in 2017. Flutter apps compile ahead-of-time to native ARM/x64/JS code and render using a custom GPU-accelerated engine (Skia, now being replaced by Impeller for better iOS performance). Used by Google Ads, Alibaba, BMW, Toyota, Canonical, and many more.

- **Repo**: https://github.com/flutter/flutter
- **Stars**: 175K+
- **Language**: Dart
- **License**: BSD 3-Clause

## What Flutter Does

- **Cross-platform** — iOS, Android, Web, macOS, Windows, Linux, embedded
- **Widget-based UI** — everything is a widget, composition over inheritance
- **Hot reload** — sub-second UI updates during development
- **Skia/Impeller** — custom rendering engine, pixel-perfect across platforms
- **Material Design 3** — Material widgets with theming
- **Cupertino widgets** — iOS-style controls
- **State management** — Provider, Riverpod, Bloc, GetX, Redux
- **Packages** — 40,000+ on pub.dev
- **Native integration** — method channels + Pigeon for type-safe bridges
- **DevTools** — profiling, widget inspector, network, CPU/memory

## Architecture

Dart source compiles to native ARM64/x64 for release (AOT) or interpreted via the Dart VM in debug (JIT) enabling hot reload. UI is a tree of widgets that Flutter rasterizes with its own rendering engine on top of the platform canvas. Native plugins bridge platform APIs via method channels.

## Self-Hosting

Open-source SDK. Install locally.

## Key Features

- Single codebase for 6 platforms
- Hot reload and hot restart
- Custom rendering engine (Skia / Impeller)
- Material Design 3
- Cupertino (iOS) widgets
- Huge widget library
- 40,000+ packages on pub.dev
- DevTools profiler
- Firebase integration
- Custom animations and gestures

## Comparison

| Framework | Language | Rendering | Platforms |
|---|---|---|---|
| Flutter | Dart | Own engine | 6 |
| React Native | JS/TS | Native components | iOS, Android, Web (sub) |
| SwiftUI | Swift | Apple | Apple only |
| Jetpack Compose | Kotlin | Android | Android + Desktop |
| .NET MAUI | C# | Native components | 4 |
| Qt | C++/QML | Own engine | 6+ |

## 常见问题 FAQ

**Q: Flutter vs React Native？**
A: Flutter 自绘 UI（视觉完全一致但像素看上去非原生感）；RN 桥接原生组件（更原生观感但跨平台差异需要处理）。Flutter 性能更稳定，RN 生态和 JS 社区更大。

**Q: 支持 Web 生产吗？**
A: 支持，但首屏较大（Dart runtime + CanvasKit）。适合 app-like SPA，不适合 SEO 站点。

**Q: Impeller 是什么？**
A: Flutter 新渲染后端，取代 Skia。在 iOS 上解决 shader compilation jank 问题，是未来标准。

## 来源与致谢 Sources

- Docs: https://docs.flutter.dev
- GitHub: https://github.com/flutter/flutter
- License: BSD 3-Clause

---
Source: https://tokrepo.com/en/workflows/7cce6fed-3606-11f1-9bc6-00163e2b0d79
Author: Script Depot