如何动态地翻译flutter中的语言？

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      localizationsDelegates: [
        GlobalMaterialLocalizations.delegate,
        GlobalWidgetsLocalizations.delegate,
      ],
      supportedLocales: [
        const Locale('en', 'US'), // 英语
        const Locale('zh', 'CN'), // 中文
        // 添加其他语言和地区的支持
      ],
      title: 'My App',
      home: MyHomePage(),
    );
  }
}

import 'package:flutter/material.dart';
import 'package:flutter/foundation.dart' show SynchronousFuture;
import 'package:flutter/widgets.dart';

class AppLocalizations {
  AppLocalizations(this.locale);

  final Locale locale;

  // 定义一个静态方法来获取该类的实例
  static AppLocalizations of(BuildContext context) {
    return Localizations.of<AppLocalizations>(context, AppLocalizations);
  }

  // 定义一个静态的代理类，用于加载不同语言的翻译文本
  static const LocalizationsDelegate<AppLocalizations> delegate =
      _AppLocalizationsDelegate();

  Map<String, String> _localizedStrings;

  // 加载对应语言的翻译文本
  Future<bool> load() async {
    String jsonString =
        await rootBundle.loadString('assets/i18n/${locale.languageCode}.json');
    Map<String, dynamic> jsonMap = json.decode(jsonString);

    _localizedStrings =
        jsonMap.map((key, value) => MapEntry(key, value.toString()));

    return true;
  }

  // 获取翻译文本
  String translate(String key) {
    return _localizedStrings[key];
  }
}

// 自定义一个继承自LocalizationsDelegate的代理类
class _AppLocalizationsDelegate
    extends LocalizationsDelegate<AppLocalizations> {
  const _AppLocalizationsDelegate();

  @override
  bool isSupported(Locale locale) {
    return ['en', 'zh'].contains(locale.languageCode);
  }

  @override
  Future<AppLocalizations> load(Locale locale) async {
    AppLocalizations localizations = AppLocalizations(locale);
    await localizations.load();
    return localizations;
  }

  @override
  bool shouldReload(_AppLocalizationsDelegate old) => false;
}

{
  "hello": "Hello",
  "world": "World"
}

{
  "hello": "你好",
  "world": "世界"
}

class MyHomePage extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    AppLocalizations localizations = AppLocalizations.of(context);

    return Scaffold(
      appBar: AppBar(
        title: Text(localizations.translate('hello')), // 获取翻译文本
      ),
      body: Center(
        child: Text(localizations.translate('world')), // 获取翻译文本
      ),
    );
  }
}