[鸿蒙2025领航者闯关]： Flutter + OpenHarmony 国际化（i18n）与本地化（L10n）全指南：一套代码，服务全球用户

# pubspec.yaml
dependencies:
  flutter:
    sdk: flutter
  flutter_localizations:
    sdk: flutter

MaterialApp(
  locale: _locale, // 当前语言
  supportedLocales: [
    Locale('en', 'US'),
    Locale('zh', 'CN'),
    Locale('ar'), // 阿拉伯语（RTL）
    Locale('ja'),
  ],
  localizationsDelegates: [
    AppLocalizations.delegate,
    GlobalMaterialLocalizations.delegate,
    GlobalWidgetsLocalizations.delegate,
    GlobalCupertinoLocalizations.delegate,
  ],
  localeResolutionCallback: (deviceLocale, supportedLocales) {
    // 自动匹配最佳语言
    return deviceLocale ?? supportedLocales.first;
  },
)

lib/
└── l10n/
    ├── app_en.arb
    ├── app_zh.arb
    ├── app_ar.arb
    └── app_ja.arb

{
  "appName": "智慧出行",
  "welcomeMessage": "欢迎，{name}！",
  "settings": "设置",
  "dateFormat": "{year}年{month}月{day}日",
  "@welcomeMessage": {
    "description": "欢迎语，含用户名占位符",
    "placeholders": {
      "name": {
        "type": "String",
        "example": "张三"
      }
    }
  }
}

// ✅ 正确：自动适配 LTR/RTL
Padding(
  padding: EdgeInsets.symmetric(horizontal: 16), // 使用 horizontal
  child: Text(S.of(context).settings),
)

// ❌ 错误：硬编码 left
Padding(
  padding: EdgeInsets.only(left: 16), // RTL 下错位
)

// 在阿拉伯语环境下启动
flutter run --dart-define=FLUTTER_LOCALE=ar

import 'package:intl/intl.dart';

// 日期
final date = DateFormat.yMMMd(_locale.toString()).format(DateTime.now());

// 数字（千分位）
final number = NumberFormat('#,##0', _locale.toString()).format(1234567);

// 货币
final price = NumberFormat.simpleCurrency(locale: _locale.toString()).format(99.99);

// 获取系统区域设置
final systemLocale = await OhDeviceInfo.getSystemLocale(); // 返回 'zh-CN'

void switchLanguage(Locale newLocale) {
  setState(() {
    _locale = newLocale;
  });
  // 持久化选择
  SharedPreferences.getInstance().then((prefs) {
    prefs.setString('user_locale', newLocale.languageCode);
  });
}

# 检查所有 ARB 是否包含相同 key
flutter pub run intl_utils:generate
# 若缺失 key，构建失败

# analysis_options.yaml
linter:
  rules:
    - prefer_const_literals_to_create_immutables
analyzer:
  errors:
    invalid_use_of_visible_for_testing_member: error

OhLocaleManager.addListener((newLocale) {
  if (_locale != newLocale) {
    switchLanguage(newLocale);
  }
});