Flutter:我想创建一个全局变量。关闭应用程序后，可将其保存以供下次再次打开应用程序时使用

dependencies:
  flutter:
    sdk: flutter
  provider: ^6.0.0

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

class MyData extends ChangeNotifier {
  String myVariable = 'Hello World';

  void updateVariable(String newValue) {
    myVariable = newValue;
    notifyListeners();
  }
}

void main() {
  runApp(
    ChangeNotifierProvider(
      create: (context) => MyData(),
      child: MyApp(),
    ),
  );
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'My App',
      home: MyHomePage(),
    );
  }
}

class MyHomePage extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    final myData = Provider.of<MyData>(context);

    return Scaffold(
      appBar: AppBar(
        title: Text('My App'),
      ),
      body: Center(
        child: Text(myData.myVariable),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: () {
          myData.updateVariable('New Value');
        },
        child: Icon(Icons.update),
      ),
    );
  }
}