要将数据传递给有状态小部件，首先要创建两个页面。现在从第一页打开第二页并传递数据。

class PageTwo extends StatefulWidget {
  final String title;
  final String name;

  PageTwo ({ this.title, this.name });

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

class PageTwoStateState extends State<PageTwo> {
  @override
  Widget build(BuildContext context) {
      return Text(
         widget.title,
         style: TextStyle(
               fontSize: 18, fontWeight: FontWeight.w700),
               ),
  }
}

class PageOne extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialButton(
          text: "Open PageTwo",
          onPressed: () {
                var destination = ServicePage(
                   title: '<Page Title>',
                   provider: '<Page Name>',
                );
                Navigator.push(context,
                    MaterialPageRoute(builder: (context) => destination));
                        },);
  }
}

@Rémi Rousselet， @Sanjayrajsinh， @Daksh Shah也更好。但我也定义了这是从起点开始的。哪个参数就是哪个值

   import 'package:flutter/material.dart';
    
    
    void main() => runApp(MyApp());
    
    class MyApp extends StatelessWidget {
      String name = "Flutter Demo";
      String description = "This is Demo Application";
    
      @override
      Widget build(BuildContext context) {
        return MaterialApp(
          home: MainActivity(
            appName: name,
            appDescription: description,
          ),
        );
      }
    }
    
    class MainActivity extends StatefulWidget {
      MainActivity({Key key, this.appName, this.appDescription}) : super(key: key);
      var appName;
      var appDescription;
    
      @override
      _MainActivityState createState() => _MainActivityState();
    }
    
    class _MainActivityState extends State<MainActivity> {
      @override
      Widget build(BuildContext context) {
        return Scaffold(
          appBar: AppBar(
            title: Text(widget.appName),
          ),
          body: Scaffold(
            body: Center(
              child: Text(widget.appDescription),
            ),
          ),
        );
      }
    }

最好的方法是不要使用State类的构造函数将参数传递给它。您可以使用widget.myField在State类中轻松访问。

例如

class UserData extends StatefulWidget {
  final String clientName;
  final int clientID;
  const UserData(this.clientName,this.clientID);

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

class UserDataState extends State<UserData> {
  @override
  Widget build(BuildContext context) {
    // Here you direct access using widget
    return Text(widget.clientName); 
  }
}

在导航屏幕时传递数据:

 Navigator.of(context).push(MaterialPageRoute(builder: (context) => UserData("WonderClientName",132)));

用于传递初始值(不向构造函数传递任何东西)

class MyStateful extends StatefulWidget {
  final String foo;

  const MyStateful({Key key, this.foo}): super(key: key);

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

class _MyStatefulState extends State<MyStateful> {
  @override
  void initState(){
    super.initState();
    // you can use this.widget.foo here
  }

  @override
  Widget build(BuildContext context) {
    return Text(foo);
  }
}

要将数据传递给有状态小部件，首先要创建两个页面。现在从第一页打开第二页并传递数据。

class PageTwo extends StatefulWidget {
  final String title;
  final String name;

  PageTwo ({ this.title, this.name });

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

class PageTwoStateState extends State<PageTwo> {
  @override
  Widget build(BuildContext context) {
      return Text(
         widget.title,
         style: TextStyle(
               fontSize: 18, fontWeight: FontWeight.w700),
               ),
  }
}

class PageOne extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialButton(
          text: "Open PageTwo",
          onPressed: () {
                var destination = ServicePage(
                   title: '<Page Title>',
                   provider: '<Page Name>',
                );
                Navigator.push(context,
                    MaterialPageRoute(builder: (context) => destination));
                        },);
  }
}

The best practice is to define the stateful widget class as immutable which means defining all dependencies (arrival parameter) as final parameters. and getting access to them by widget.<fieldName> in the state class. In case you want to change their values like reassigning you should define the same typed properties in your state class and re-assign them in the initState function. it is highly recommended not to define any not-final property in your stateful widget class and make it a mutable class. something like this pattern:

class SomePage extends StatefulWidget{
  final String? value;
  SomePage({this.value});

  @override
  State<SomePage> createState() => _SomePageState();
}

class _SomePageState extends State<SomePage> {
  String? _value;

  @override
  void initState(){
    super.initState();
    setState(() {
      _value = widget.value;
    });
  }

 @override
 Widget build(BuildContext context) {
    return Text(_value);
 }
}