ActiveLocalizationDelegate class

Application-owned locale loading that composes with existing Flutter delegates.

In MaterialApp add this delegate alongside Flutter SDK delegates; switch locale using app-owned state. The gallery includes asset catalogs, context.tr, interpolation, ICU and RTL. A custom loader owns resource failures and retries.

Gallery walkthrough · browser route /#/localization. These examples use the current checkout; published 1.x APIs can differ.

Load interpolation through an injected catalog

import 'package:activity/activity.dart';
import 'package:flutter/widgets.dart';

Future<void> main() async {
  WidgetsFlutterBinding.ensureInitialized();
  final delegate = ActiveLocalizationDelegate(
    supportedLocales: [const Locale('en')],
    loader: (_) async => {'hello': 'Hello {name}'},
  );
  final messages = await delegate.load(const Locale('en'));
  assert(
    messages.translate('hello', parameters: {'name': 'Ada'}) == 'Hello Ada',
  );
}

Use fallback messages

import 'package:activity/activity.dart';
import 'package:flutter/widgets.dart';

Future<void> main() async {
  WidgetsFlutterBinding.ensureInitialized();
  final delegate = ActiveLocalizationDelegate(
    supportedLocales: [const Locale('en'), const Locale('sw')],
    fallbackLocale: const Locale('en'),
    loader:
        (locale) async => locale.languageCode == 'en' ? {'save': 'Save'} : {},
  );
  final messages = await delegate.load(const Locale('sw'));
  assert(messages.translate('save') == 'Save');
  assert(
    messages.translate('missing', fallback: 'Unavailable') == 'Unavailable',
  );
}

Properties