Flutter 国际化支持实践案例

在Flutter中实现国际化，通常使用Localizations和Delegate。例如：假设你要开发一个支持中英文的App。

1. 创建资源文件：在locale/下创建en.json和zh.json，内容分别是：

   // en.json
   {"hello": "Hello", "welcome": "Welcome"}
   
   // zh.json
   {"hello": "你好", "welcome": "欢迎"}
   

2. 配置支持的语言列表，在pubspec.yaml添加：

   flutter:
     localized.Strings:
       supported-locales: en,zh
   

3. 编写本地化类继承LocalizationsDelegate：

   class DemoLocalizations {
     final Locale locale;
     DemoLocalizations(this.locale);
   
     static DemoLocalizations of(BuildContext context) {
       return Localizations.of<DemoLocalizations>(context, DemoLocalizations);
     }
   
     static Map<String, dynamic> _localizedValues;
   
     String get(String key) => _localizedValues[key];
   }
   
   class DemoLocalizationsDelegate extends LocalizationsDelegate<DemoLocalizations> {
     @override
     bool isSupported(Locale locale) => ['en', 'zh'].contains(locale.languageCode);
   
     @override
     Future<DemoLocalizations> load(Locale locale) async {
       String jsonStr = await rootBundle.loadString('locale/${locale.languageCode}.json');
       _localizedValues = json.decode(jsonStr);
       return DemoLocalizations(locale);
     }
   
     @override
     bool shouldReload(DemoLocalizationsDelegate old) => false;
   }
   

4. 在主文件中注册并使用：

   void main() {
     runApp(MaterialApp(
       localizationsDelegates: [
         DemoLocalizationsDelegate(),
         GlobalMaterialLocalizations.delegate,
         GlobalWidgetsLocalizations.delegate,
       ],
       supportedLocales: [Locale('en'), Locale('zh')],
       home: MyApp(),
     ));
   }
   
   class MyApp extends StatelessWidget {
     @override
     Widget build(BuildContext context) {
       return Text(DemoLocalizations.of(context).get('hello'));
     }
   }
   

这样就可以根据设备语言自动切换或手动选择语言了。