Sharing features among Android applications: experience feedback

What if you could build entire features, ready-to-use, and just share them to all your apps? At Deezer we tackled this challenge for the authentication, a unique library used both by Zen and Deezer.

You will learn how we manage to speed up app development, by integrating entire features in a few lines of code, while handling specific needs of each application.

Transcript

1. 10 avril 2025 Sharing features among Android applications Experience feedback Philémon Combes Jean-Baptiste Vincey
2. Philémon Combes Jean-Baptiste Vincey @philemoncombes @jbvincey 2
3. Android Makers 2022 sharing code with libraries 3
4. Core libs Design System SDK 4 2022
5. Core libs Design System SDK Feature libs 5 2025
6. Handling multiple apps A spreading trend
7. At Deezer we develop multiple apps • 2008 Deezer ? 7
8. At Deezer we develop multiple apps • 2008 Deezer • 2020 Deezer for Creators ? 8
9. At Deezer we develop multiple apps • 2008 Deezer • 2020 Deezer for Creators • 2021 Audiobooks 9
10. At Deezer we develop multiple apps • 2008 Deezer • 2020 Deezer for Creators • 2021 Audiobooks • 2023 Zen 10
11. At Deezer we develop multiple apps • 2008 Deezer • 2020 Deezer for Creators • 2021 Audiobooks • 2023 Zen • 2025/26 ? 11 ? ?
12. Feature as lib Aren’t there any risks?
13. Should a full feature be developed as a library? A simple framework to help on the decision 13
14. Should a full feature be developed as a library? A simple framework to help on the decision • Same needs between all apps? 14
15. Should a full feature be developed as a library? A simple framework to help on the decision • Same needs between all apps? AuthJourney 15
16. Should a full feature be developed as a library? A simple framework to help on the decision • Same needs between all apps? AuthJourney • Low di ff erentiation value? 16
17. Should a full feature be developed as a library? A simple framework to help on the decision • Same needs between all apps? AuthJourney • Low di ff erentiation value? AuthJourney 17
18. Should a full feature be developed as a library? A simple framework to help on the decision • Same needs between all apps? AuthJourney • Low di ff erentiation value? AuthJourney • Customization requirements well de fi ned? 18
19. Should a full feature be developed as a library? A simple framework to help on the decision • Same needs between all apps? AuthJourney • Low di ff erentiation value? AuthJourney • Customization requirements well de fi ned? AuthJourney 19
20. Project timeline
21. Timeline of module creation The MVP De fi ne a MVP for Zen 21
22. Timeline of module creation The MVP De fi ne a MVP for Zen Refactored the legacy screens and logic to
 a new library 22
23. Timeline of module creation The MVP De fi ne a MVP for Zen Refactored the legacy screens and logic to
 a new library Integrate it in Zen ✨ 23
24. Timeline of module creation Integration in the main app Complete auth methods needed by Deezer 24
25. Timeline of module creation Integration in the main app Complete auth methods needed by Deezer Integrate it in Deezer 25
26. Timeline of module creation Integration in the main app Complete auth methods needed by Deezer Integrate it in Deezer Clean all the legacy app code 🗑 26
27. Project de fi nition
28. The sample app • Guarantees feature integration
 • Helps the QA
 • Living documentation 28
29. The API behind AuthJourney.init(Config, Listener) startAuthJourney() 29 29
30. The API behind AuthJourney startAuthJourney() 30 30
31. The API behind AuthJourney startAuthJourney() 31 Emits onResult(Result<UserSession>) 31
32. Find 7 di ff erences Let’s play!
33. VS Deezer Zen 33
34. Icon Con fi guration 34
35. Icon Con fi guration 35 data class Config( val icons: Icons, … ) { data class Icons( @DrawableRes val iconBack: Int ) }
36. Theming 36 data class Config( val icons: Icons, val theme: Theme, … ) { data class Theme( val colors: Colors, val typography: Typography, val shapes: Shapes, ) }
38. UI Slots 38 data class Config( val icons: Icons, val theme: Theme, val slots: Slots, … ) { data class Slots( val header: @Composable () -> Unit, ) }
39. UI Slots 39 slots = Config.Slots( header = { Image( modifier = Modifier.fillMaxWidth(), painter = painterResource(drawable), ) } )
40. UI Slots 40 slots = Config.Slots( header = { LottieAnimation( modifier = Modifier.fillMaxWidth(), composition = composition, progress = { progress }, contentScale = ContentScale.FillBounds, dynamicProperties = dynamicProperties, ) } )
42. { "data":{ "steps_config":{ "email_or_phone":{ "title":"Email", "input_placeholder":"Email address", "phone_activated":false }, }, "registration_info_steps":[ "username", "age", "identity" ] } } Backend con fi g 42 42
43. Challenges And next steps
44. Challenges we faced • Restrain Designers creativity 44
45. Challenges we faced • Restrain Designers creativity • Time to integrate the feature in all apps 45
46. Challenges we faced • Restrain Designers creativity • Time to integrate the feature in all apps • Adapt to apps di ff erent technologies 46
47. • Google Play Billing ✔ What’s next ? Other features we could share 47
48. • Google Play Billing ✔ • Account management ✔ What’s next ? Other features we could share 48
49. • Google Play Billing ✔ • Account management ✔ • Settings❓ What’s next ? Other features we could share 49
50. • Google Play Billing ✔ • Account management ✔ • Settings❓ • Player❓ What’s next ? Other features we could share 50
51. Takeaways
52. Pros and cons of shared features + - Mutualize e ff ort Additional initial cost Easier maintenance Harder to customize Evolution bene fi ts all Cannot evolve independently (Faster development) (Or not?) 52
53. When to share features • Same needs between all apps? • Low di ff erentiation value? • Customization requirements well de fi ned? 53
54. How to share features • De fi ne the API • Build with sample app • Choose customization level 54
55. Thanks! 55