Android MVP pattern and multi presenter Activities

This presentation describes the MVP architectural pattern on Android and its main theory of the separation of concerns. Also presents a variation implemented and used by the Android team of Taxibeat, regarding the implementation of multiple Presenters and Views in a single Android Activity.

Transcript

1. Android MVP (Model View Presenter) pattern and multi-Presenter Activities. Chryssa Aliferi Android Software Engineer ChryssaAliferi
2. Our beloved Android
3. Our beloved Android: The business logic and UI logic coexist in the Activity classes:
4. Our beloved Android: Everything is connected with everything. UI + Business Logic + Data + Multiple Threads = Android GOD Activity
5. What is MVP?
6. MVP stands for? Most Valuable Player
7. MVP stands for? Minimum Viable Product
8. What is MVP? Model View Presenter: Separates the presentation layer from the logic. MVP stands for:
9. What is MVP? Model View Presenter: MVP stands for:
10. What is MVP? Model: is a data layer such as database or a set of classes that provide the data we want to display in the view. View: represents the UI components and transforms the information contained by the model into the UI. Presenter: is a layer that provides View with data from Model, according to some rules.
11. MVP Model Model: • Set of classes that define the data. • Business rules for data and data transformations • Data Retrieval
12. View: • Activity, Fragment, View, Dialog • Reference to the Presenter • Exposes methods and Events to the presenter • Transforms the information contained by the model into the UI. • Animations • Navigating to other screens MVP View
13. Presenter: • Middle man between View and Model • Controls and updates UI • Handles all UI events on behalf of the view • Retrieves data from the Model layer and displays them in the View MVP Presenter
14. How to implement MVP?
15. • View interface - “Screen” • all “Screen” methods refer to view behaviour • Android Activity • “screen” methods implemented • Presenter class & Presenter “children” flows • accesses view through screen MVP Implementation
16. MVP Example A new screen concerning the Payment feature, with two modes:
 • Select Payment • Edit Payment
17. PaymentActivity Without MVP:
18. PaymentScreen.java interface:
19. PaymentActivity With MVP:
20. PaymentPresenter.java:
21. MVP Example What about multi- Presenter Activities? Let’s try this again…
22. PaymentScreen.java interface:
23. PaymentActivity with multiple presenters:
24. PaymentPresenter with multiple presenters:
25. EditPaymentFlow.java :
26. SelectPaymentFlow.java :
27. Taxibeat MVP Example The Taxibeat PaymentMeans Activity Case.
28. Taxibeat PaymentActivity.java :
29. Taxibeat MVP Example Another Taxibeat case: Multi-Presenter Activities
30. Taxibeat LocateActivity.java: • LocateActivity.java is the Main Taxibeat Activity • LocateActivity.java contains 2 basic Presenters, the LocatePresenter.java and the MenuPresenter.java • LocatePresenter.java has 3 presenter flow descendants, the PickupFlow.java, the DropOffFlow.java and the CallingFlow.java
31. PickupFlow.java • LocatePresenter.java descendant • PickupFlow.java presenter contains all the logic behind the process of setting the correct pickup location. • onAddressAnimationEnd(), PickupFlow calls “destroys” itself and gives control to DropOffFlow. • onBackButton() press we terminate the app.
32. DropOffFlow.java • LocatePresenter.java descendant • DropOffFlow.java presenter contains all the logic behind the process of setting the dropoff location and all the hailing options. • onClick() of the green button, DropOffFlow “destroys” itself and gives control to CallingFlow. • onBackButton() press we handle back control to the PickupFlow.
33. CallingFlow.java • LocatePresenter.java descendant • CallingFlow presenter contains all the logic behind the process of calling a taxi. • onClick() of the red button or on onBackButton() press, CallingFlow “destroys” itself • Then gives control back to DropOffFlow.
34. MenuPresenter.java • MenuPresenter presenter contains all the logic behind the menu initialisation and menu onClick actions. • MenuPresenter is an autonomous presenter that handles only menu actions.
35. LocateActivity contains: LocatePresenter MenuPresenter PickupFlow CallingFlow DropOffFlow MenuScreen LocateScreen
36. MVP Recap
37. MVP Pros vs Cons Pros: • Separation of concerns • Maintainability • Re-usability of views, presenters and screens • Less time spending on view control • Information hiding • Testable! Cons: • Redundancy • Learning curve • Takes time, not suitable for small projects.
38. MVP Do not forget: • Use your logic, to distinguish the main business flows • Create your “Screen”, your View interface • Activities, Fragments or custom views implement the View interface • Separate your app business logic by moving it to a plain java Presenter object • Make Presenter “children” if needed to make your code even cleaner • Spend time writing a clean interface between your Presenter and your View • Test your Presenter. • Retain the state of the Presenters, “initialise” and “destroy” them.
39. § GitHub Project https://github.com/ChryssaAliferi/MultiPresenterMVP
40. The End! Any Questions?
41. www.taxibeat.com/careers We are hiring!
42. Resources: • Is Activity GOD? by Kenju Wagatsuma on SlideShare • MVP design pattern for Android Apps by Infinum on SlideShare • Android Code That Scales, With MVP by Nathan Barraille • MVP for Android: how to organize the presentation layer by Antonio Leiva • Introduction to Model View Presenter on Android by Konstantin Mikheev
43. § Thank you! Chryssa Aliferi Android Software Engineer ChryssaAliferi