颤振定位

Question

我是Flutter本地化的新手。我正在尝试在抖动的IOS应用中添加它，但是出现以下错误：

方法“翻译”在null上被调用。 接收者：null 尝试调用：translate（“ menu”）

我希望有人可以帮我解决这个问题-我已经尝试了好几个小时，但无法解决问题-希望你能提供帮助

主要：

import 'package:flutter/material.dart';
import 'package:flutter_localizations/flutter_localizations.dart';
import 'package:xobrew_app/services/app_localizations.dart';


class forside extends StatefulWidget {
  @override
  _forsideState createState() => _forsideState();
}

class _forsideState extends State<forside> {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(

      supportedLocales: [
        Locale('en', 'US'),
        Locale('da', 'DK'),
      ],
      localizationsDelegates: [
        AppLocalizations.delegate,
        GlobalMaterialLocalizations.delegate,
        GlobalWidgetsLocalizations.delegate,
      ],
      localeResolutionCallback: (locale, supportedLocales) {
        if (locale == null) {
          return supportedLocales.first;
        }
        for (var supportedLocales in supportedLocales ) {
          if(supportedLocales.languageCode == locale.languageCode &&
              supportedLocales.countryCode == locale.countryCode) {
            return supportedLocales;
          }
       }
        return supportedLocales.first;
      },

      home: Scaffold(
        appBar: AppBar(
          title: Text('Brew App'),
          backgroundColor: Colors.green[800],

        ),
        backgroundColor: Colors.green[100],
        body: Container(
          padding: EdgeInsets.all(30.0),
          child: GridView.count(
            crossAxisCount: 2,
            children: <Widget>[
              Card(
                  margin: EdgeInsets.all(8.0),
                  child: InkWell(
                    onTap: (){},
                    splashColor: Colors.green,
                    child: Center(
                      child: Column(

                        mainAxisSize: MainAxisSize.min,
                        children: <Widget>[
                          Icon(Icons.add_box, size: 70.0, color: Colors.orange,),
                          Text("Calculator", style: TextStyle(fontSize: 17.0)),
                        ],
                      ),
                    ),
                  )

              ),
              Card(
                  margin: EdgeInsets.all(8.0),
                  child: InkWell(
                    onTap: (){},
                    splashColor: Colors.green,
                    child: Center(
                      child: Column(

                        mainAxisSize: MainAxisSize.min,
                        children: <Widget>[
                          Icon(Icons.local_library, size: 70.0, color: Colors.blue,),
                          Text(
                              //"Knowledge",

                              AppLocalizations.of(context).translate('menu'),
                              style: TextStyle(fontSize: 17.0)),
                        ],
                      ),
                    ),
                  )

              ),


            ],

          ),
        ),
      ),
    );
  }
}

app_localization

import 'dart:async';
import 'dart:convert';


import 'package:flutter/material.dart';
import 'package:flutter/services.dart';

class AppLocalizations {

  final Locale locale;
  AppLocalizations(this.locale);

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

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

  Map<String, String> _localizedStrings;

  Future<bool> load() async {
    // Load the language JSON file from the "lang" folder
    String jsonString =
        await rootBundle.loadString('lang/${locale.languageCode}.json');
    //print(locale.languageCode);
    //await rootBundle.loadString('lang/${locale.languageCode}.yaml');





    Map<String, dynamic> jsonMap = json.decode(jsonString);

    _localizedStrings = jsonMap.map((key, value){
      //print (_localizedStrings);
      //print (locale);
      return MapEntry(key, value.toString());
    });

    return true;

  }
  String translate(String key) {
    return _localizedStrings[key];
  }
}

//LocalizationsDelegate is a factory for a set of localized resources

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

  @override
  bool isSupported(Locale locale) {
    //Include all of your supported language codes here
    return ['en', 'da'].contains(locale.languageCode);
  }
  @override
  Future<AppLocalizations> load(Locale locale) async {
    AppLocalizations localizations = AppLocalizations(locale);
    await localizations.load();
    return localizations;
  }
  @override
  bool shouldReload(_AppLocalizationsDelegate old) => false;



}