platform aware switch widget

platform_switch.dart

// Copyright (c) 2019, the Dart project authors.  Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.

import 'package:flutter/material.dart';
import 'package:flutter/cupertino.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      debugShowCheckedModeBanner: false,
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, this.title}) : super(key: key);

  final String title;

  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            PlatformSwitch(platform: 'cupertino'),
            PlatformSwitch(),
          ],
        ),
      ),
    );
  }
}

/// [PlatformSwitch] 는 각 플랫폼에 맞는 스위치 위젯을 렌더링합니다.
/// 이 에제에서는 [platform] 이라는 String 속성을 사용하지만,
/// 실제 프로젝트에서 사용할 때는 `import 'dart:io' show Platform;` 라이브러리를 이용하여야합니다.
/// 사용방법은 [Platform.isAndroid] 또는 [Platform.isIOS] 로
/// 해당 플랫폼에 맞는 [build] 메소드를 구현해야합니다.
class PlatformSwitch extends StatefulWidget {
  final String platform;

  PlatformSwitch({this.platform});

  @override
  _PlatformSwitchState createState() => _PlatformSwitchState();
}

class _PlatformSwitchState extends State<PlatformSwitch> {
  bool _value = false;
  ValueChanged<bool> _onChanged;
  @override
  Widget build(BuildContext context) {
    if (widget.platform == 'cupertino') {
      return CupertinoSwitch(value: _value, onChanged: onChanged);
    }
    return Switch(value: _value, onChanged: onChanged);
  }

  onChanged(bool value) {
    setState(() {
      _value = value;
    });
    _onChanged(_value);
  }
}