[FlutterTokyo#10]In-App Language Switching in Flutter

This is the slide, "In-App Language Switching in Flutter" on the mobile seminar.
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Transcript

1. 2025.09.03 Kenichi Kambara (@korodroid) Flutter Tokyo #10 In-App Language Switching in Flutter
2. About me •Mobile App Development •Speeches (e.g. 20+ Int’l/100+ Domestic) •Writings (e.g. 10 Dev Books) •[Of fi cial] Evangelist at NTT TechnoCross •[Private] iplatform.org ਆݪ ݈Ұ (X:@korodroid) NEW
3. About my product (Personal projects) Sekaiphone Pro(Flutter(+Kotlin/Swift))
4. Today’s topic
5. 1. Why In-App Language Switching Matters •Changing OS language is inconvenient for users •Tourists, global teams, and multilingual users need fl exibility •Improves user experience and inclusivity •Easier testing and localization for developers 
6. 2. Strategy for Language Switching • fl utter_localizations of fi cial localization support •slang_ fl utter simpli fi es localization with type-safe 
7. 2. What if you only use one?  Scenario What works What’s missing fl utter_localizations only Framework UI localized, date/ number formatting, RTL support App strings must be handled manually, no type safety, in-app switching requires custom logic slang_ fl utter only App strings managed, instant switching, type safety, fallback Framework widgets stay in English, no proper date/number/ RTL support
8. 3-1. Translation Files 
9. 3-2. Generate Code (JSON->Dart)  // strings.g.dart Dart
10. 4. App Initialization 
11. 5. Using Translations  ➡ Type-safe access, automatic UI refresh
12. 6. Language Switching UI  ➡ Users can switch instantly, see current selection
13. 7. More Complex Examples 
14. Wrap-Up 1.Create translation fi les 2.Generate code (slang_build_runner) 3.Wrap app with TranslationProvider 4.Con fi gure MaterialApp 5.Switch language via LocaleSettings.setLocale() 6.UI updates automatically 
15. Key takeaway In-app language switching enhances UX and empowers users with multilingual fl exibility. 
16. Please let me know if you have any requests such as technical speeches, technical writings and so on. Facebook:http://fb.com/kanbara.kenichi X:@korodroid LinkedIn:http://www.linkedin.com/in/korodroid Thank you so much