找不到实现。 Appbar窗口小部件要求翻译后由Localizations窗口小部件祖先错误提供MaterialLocaliztions

Question

我已经尝试过answer和this one too。

我在控制台上收到的错误异常是

在尝试翻译之前，这是下面的应用状态

我立即尝试翻译，我在屏幕上看到此错误，并且应用程序栏完全消失。

这是我的翻译功能

void _changeLanguage(AppLocalModel languageCode, BuildContext context) async {
    Locale _temp;
    switch (languageCode.languageCode) {
      case ENGLISH:
        _temp = Locale(languageCode.languageCode, "US");
        break;
      case JUKUN:
        _temp = Locale(languageCode.languageCode, "NG");
        break;
      case TIV:
        _temp = Locale(languageCode.languageCode, "NG");
        break;
      case AGATU:
        _temp = Locale(languageCode.languageCode, "NG");
        break;
      case HAUSA:
        _temp = Locale(languageCode.languageCode, "NG");
        break;
      default:
        _temp = Locale(languageCode.languageCode, "US");
    }
    App.setLocale(context, _temp);

    setState(() {});
  }

这是我的main()

需要注意的是我的主应用是有状态的小部件，因为我有一个仅在首次启动时显示的屏幕

void main() {

  runApp(App());
}

class App extends StatefulWidget {
  static void setLocale(BuildContext context, Locale locale) {
    _App _app = context.findAncestorStateOfType<_App>();
    _app.setLocale(locale);

  }

  _App createState() => _App();
}

class _App extends State<App> {

  Locale _locale;
  void setLocale(Locale locale) {
    setState(() {
      _locale = locale;
    });
  }

  @override
  void didChangeDependencies() {
    super.didChangeDependencies();
    getLocale().then((locale) {
      this._locale = locale;
    });
  }

  @override
  void initState() {
    super.initState();

    getLocale().then((locale) {
      this._locale = locale;
    });
  }
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'My app',
      locale: _locale,
      // actions: ActionsWidget,
      localizationsDelegates: [
        // ... app-specific localization delegate[s] here
        AppLocalization.delegate,
        GlobalMaterialLocalizations.delegate,
        GlobalWidgetsLocalizations.delegate,
        GlobalCupertinoLocalizations.delegate,
      ],
      localeResolutionCallback: (deviceLocale, supportedLocale) {
        for (var locale in supportedLocale) {
          if (locale.languageCode == deviceLocale.languageCode &&
              locale.countryCode == deviceLocale.countryCode) {
            return deviceLocale;
          }
        }
        return supportedLocale.first;
      },
      supportedLocales: [
        const Locale(ENGLISH, "US"), // English
        const Locale(HAUSA, "NG"), // Housa
        const Locale(AGATU, "NG"), // Hebrew
        const Locale(JUKUN, "NG"), // Jukun
        const Locale(TIV, "NG"), // Tiv
        // ... other locales the app supports
      ],
      home: Welcome(),
      );
    }
}