How to programmatically change the locale in Flutter? 

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

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

class MyApp extends StatelessWidget {
  const MyApp({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return ChangeNotifierProvider(
      create: (context) => LocaleModel(),
      child: Consumer<LocaleModel>(
        builder: (context, localeModel, child) => MaterialApp(
          title: 'Your app title',
          localizationsDelegates: AppLocalizations.localizationsDelegates,
          supportedLocales: AppLocalizations.supportedLocales,
          locale: localeModel.locale,
          /* ... */
        ),
      ),
    );
  }
}

class LocaleModel extends ChangeNotifier {
  Locale? _locale;

  Locale? get locale => _locale;

  void set(Locale locale) {
    _locale = locale;
    notifyListeners();
  }
}