i18n

 MaterialApp(

  title: '',
  theme: ThemeData(
    colorScheme: ColorScheme.fromSeed(seedColor: Colors.black),
    scaffoldBackgroundColor: Color(globalBackgroundColor),
    useMaterial3: true,
  ),
  home: const MyHomePage(title: ''),
  localizationsDelegates: [
    FlutterI18nDelegate(
      translationLoader: FileTranslationLoader(
        decodeStrategies:  [JsonDecodeStrategy()],
        useCountryCode: true,
        fallbackFile: 'en_US',
        basePath: 'assets/i18n',
      ),
      missingTranslationHandler: (key, locale) {
        print("--- Missing Key: $key, languageCode: ${locale!.languageCode.toString()}");
      },
    ),

  ],
);

change language

InkWell(
    onTap:() async {
      await FlutterI18n.refresh(context,Locale('en', 'US') );
      print( FlutterI18n.currentLocale(context) );
      print('5641:'+FlutterI18n.translate(context, "hw") );

    },
    child: Container(width: 20,height: 20,color: Colors.grey,)),

pubspec.yaml

flutter:

  # The following line ensures that the Material Icons font is
  # included with your application, so that you can use the icons in
  # the material Icons class.
  uses-material-design: true

  assets:
    - assets/
    - assets/i18n/