如何在Flutter中的自定义底部栏和下拉列表中显示不同的语言？

dependencies:
  flutter_localizations:
    sdk: flutter

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

class AppLocalizations {
  static const LocalizationsDelegate<AppLocalizations> delegate =
      _AppLocalizationsDelegate();

  static AppLocalizations of(BuildContext context) {
    return Localizations.of<AppLocalizations>(context, AppLocalizations);
  }

  String get title {
    return Intl.message(
      'App Title',
      name: 'title',
      desc: 'Title for the application',
    );
  }

  // 添加其他需要翻译的文本
  // ...

  // 支持的语言列表
  static const List<Locale> supportedLocales = [
    Locale('en', 'US'), // 英语
    Locale('zh', 'CN'), // 中文
  ];
}

class _AppLocalizationsDelegate
    extends LocalizationsDelegate<AppLocalizations> {
  const _AppLocalizationsDelegate();

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

  @override
  Future<AppLocalizations> load(Locale locale) {
    return SynchronousFuture<AppLocalizations>(AppLocalizations());
  }

  @override
  bool shouldReload(_AppLocalizationsDelegate old) {
    return false;
  }
}

import 'package:flutter/material.dart';
import 'package:flutter_localizations/flutter_localizations.dart';
import 'package:your_app/l10n/intl.dart';

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      localizationsDelegates: [
        AppLocalizations.delegate,
        GlobalMaterialLocalizations.delegate,
        GlobalWidgetsLocalizations.delegate,
      ],
      supportedLocales: AppLocalizations.supportedLocales,
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: MyHomePage(),
    );
  }
}

class MyHomePage extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(AppLocalizations.of(context).title),
      ),
      body: Center(
        child: Text(
          AppLocalizations.of(context).helloWorld,
          style: TextStyle(fontSize: 24),
        ),
      ),
      bottomNavigationBar: BottomNavigationBar(
        items: [
          BottomNavigationBarItem(
            icon: Icon(Icons.home),
            label: AppLocalizations.of(context).home,
          ),
          BottomNavigationBarItem(
            icon: Icon(Icons.settings),
            label: AppLocalizations.of(context).settings,
          ),
        ],
      ),
    );
  }
}

class MyHomePage extends StatelessWidget {
  int _currentIndex = 0;

  void _onTabTapped(int index) {
    _currentIndex = index;
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(AppLocalizations.of(context).title),
      ),
      body: Center(
        child: Text(
          AppLocalizations.of(context).helloWorld,
          style: TextStyle(fontSize: 24),
        ),
      ),
      bottomNavigationBar: BottomNavigationBar(
        currentIndex: _currentIndex,
        onTap: _onTabTapped,
        items: [
          BottomNavigationBarItem(
            icon: Icon(Icons.home),
            label: AppLocalizations.of(context).home,
          ),
          BottomNavigationBarItem(
            icon: Icon(Icons.settings),
            label: AppLocalizations.of(context).settings,
          ),
        ],
      ),
    );
  }
}

class MyHomePage extends StatelessWidget {
  // ...

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(AppLocalizations.of(context).title),
      ),
      body: Center(
        child: Text(
          AppLocalizations.of(context).helloWorld,
          style: TextStyle(fontSize: 24),
        ),
      ),
      bottomNavigationBar: BottomNavigationBar(
        // ...
      ),
      floatingActionButton: DropdownButton(
        value: AppLocalizations.of(context).locale.languageCode,
        items: AppLocalizations.supportedLocales.map((Locale locale) {
          return DropdownMenuItem(
            value: locale.languageCode,
            child: Text(locale.languageCode),
          );
        }).toList(),
        onChanged: (String value) {
          Locale newLocale = Locale(value);
          AppLocalizations.delegate.load(newLocale).then((_) {
            runApp(MyApp());
          });
        },
      ),
    );
  }
}