Flutter returns null for AppLocalization.of(context)

Question

I am using Flutter to build a Web-App and I want to use the internationalization feature of flutter on my new app. I was following the Flutter-Tutorial and I try to set the app-title using the arb-file. As mentioned in the tutorial, the app_localization.dart-files are created properly for 'en' and 'de'. Yet, I get a null pointer exception in the following code.

import 'package:flutter/material.dart';
import 'package:flutter_localizations/flutter_localizations.dart';
import 'package:flutter_gen/gen_l10n/app_localizations.dart';

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'MyApp',
      localizationsDelegates: [
        AppLocalizations.delegate, // Post-EDIT due to croxx5f
        GlobalMaterialLocalizations.delegate,
        GlobalWidgetsLocalizations.delegate,
        GlobalCupertinoLocalizations.delegate,
      ],
      supportedLocales: [
        Locale('de', ''),
        Locale('en', ''),
      ],
      theme: ThemeData(
        primarySwatch: Colors.red,
      ),
      home: Scaffold(
        appBar: AppBar(
          title: Text(AppLocalizations.of(context)!.appTitle),
        ),
        body: Text(AppLocalizations.of(context)!.appTitle)
      ),
    );
  }
}

In fact, AppLocalizations.of(context) returns null.

Answer 1

You should add the AppLocalizations in your MaterialApp:

MaterialApp(
...
      localizationsDelegates: const [
        AppLocalizations.delegate,
        GlobalMaterialLocalizations.delegate,
      ],
      supportedLocales: AppLocalizations.supportedLocales,
...

Answer 2

Thats helped me. I had a CupertinoApp above MaterielApp, this override the MaterielApp and my AppLocalization.of(content) was null

https://github.com/flutter/flutter/issues/26365#issuecomment-523536339