import 'package:flutter/material.dart';

void main() {

  runApp(MaterialApp(

    title: "Switch",

    home: MyApp(),

  ));

}

class MyApp extends StatefulWidget {

  @override

  _MyAppState createState() => _MyAppState();

}

class _MyAppState extends State<MyApp> {

  bool flag = false;

  @override

  Widget build(BuildContext context) {

    return Scaffold(

      appBar: AppBar(title: Text("Switch")),

      body: Column(

        mainAxisAlignment: MainAxisAlignment.center,

        children: <Widget>[

          Switch(

            value: this.flag,

            activeColor: Colors.red,

            onChanged: (value) {

              setState(() {

                this.flag = value;

              });

            },

          ),

          Text("此时的状态是${this.flag == true ? "选中" : "未选中"}")

        ],

      )

    );

  }

}