checkbox 是一个开关控件，这个控件主要是起到了开关功能，如下图：

image.png

代码如下：

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

/**
 * 开关控件
 */
void main() {
  runApp(myApp());
}

class myApp extends StatelessWidget{

  @override
  Widget build(BuildContext context) {
    // TODO: implement build
    return MaterialApp(
      title: 'fade demo',
      theme: ThemeData(
        primarySwatch: Colors.blue
      ),
      home: CupertinoSwitchDemo()
    );
  }
}

class CupertinoSwitchDemo extends StatefulWidget{

  @override
  State<StatefulWidget> createState() {
    // TODO: implement createState
    return _CupertinoSwitchDemo();
  }
}


class _CupertinoSwitchDemo extends State<CupertinoSwitchDemo>{

  bool _value = true;

  @override
  Widget build(BuildContext context) {
    // TODO: implement build
    return Center(
      child: CupertinoSwitch(
          value: _value,
          onChanged: (bool value){
            setState(() {
              _value = value;
            });
          },
        activeColor: Colors.red,
      ),
    );
  }

}