localizationsDelegates property

The delegates for this app's Localizations widget.

The delegates collectively define all of the localized resources for this application's Localizations widget.

Internationalized apps that require translations for one of the locales listed in GlobalMaterialLocalizations should specify this paramter and list the supportedLocales that the application can handle.

import 'package:flutter_localizations/flutter_localizations.dart';
MaterialApp(
  localizationsDelegates: [
    // ... app-specific localization delegate[s] here
    GlobalMaterialLocalizations.delegate,
    GlobalWidgetsLocalizations.delegate,
  ],
  supportedLocales: [
    const Locale('en', 'US'), // English
    const Locale('he', 'IL'), // Hebrew
    // ... other locales the app supports
  ],
  // ...
)

Adding localizations for a new locale

The information that follows applies to the unusual case of an app adding translations for a language not already supported by GlobalMaterialLocalizations.

Delegates that produce WidgetsLocalizations and MaterialLocalizations are included automatically. Apps can provide their own versions of these localizations by creating implementations of LocalizationsDelegate<WidgetsLocalizations> or LocalizationsDelegate<MaterialLocalizations> whose load methods return custom versions of WidgetsLocalizations or MaterialLocalizations.

For example: to add support to MaterialLocalizations for a locale it doesn't already support, say const Locale('foo', 'BR'), one could just extend DefaultMaterialLocalizations:

class FooLocalizations extends DefaultMaterialLocalizations {
  FooLocalizations(Locale locale) : super(locale);
  @override
  String get okButtonLabel {
    if (locale == const Locale('foo', 'BR'))
      return 'foo';
    return super.okButtonLabel;
  }
}

A FooLocalizationsDelegate is essentially just a method that constructs a FooLocalizations object. We return a SynchronousFuture here because no asynchronous work takes place upon "loading" the localizations object.

class FooLocalizationsDelegate extends LocalizationsDelegate<MaterialLocalizations> {
  const FooLocalizationsDelegate();
  @override
  Future<FooLocalizations> load(Locale locale) {
    return SynchronousFuture(FooLocalizations(locale));
  }
  @override
  bool shouldReload(FooLocalizationsDelegate old) => false;
}

Constructing a MaterialApp with a FooLocalizationsDelegate overrides the automatically included delegate for MaterialLocalizations because only the first delegate of each LocalizationsDelegate.type is used and the automatically included delegates are added to the end of the app's localizationsDelegates list.

MaterialApp(
  localizationsDelegates: [
    const FooLocalizationsDelegate(),
  ],
  // ...
)

See also:

• supportedLocales, which must be specified along with localizationsDelegates.
• GlobalMaterialLocalizations, a localizationsDelegates value which provides material localizations for many languages.
• The Flutter Internationalization Tutorial, flutter.io/tutorials/internationalization/.