Cooking up Clean Architecture on Android

A talk I gave at CodeMotion Tel Aviv 2015. It covers basics of clean MVP-ish architecture on Android, with some code samples.

Transcript

1. Cooking up Clean Architecture on Android Zan Markan, Master Jedi (also Android developer)
2. Stuff We’ll Cover • What & Why & Why & What • MVP - ingredients • MVP - layer by layer • Tools • RxJava & other goodies
3. What Is Architecture, Really?
4. Examples of Architecture • MVC - asp.net MVC, lots of web • MVP - VIPER (iOS) • MVVM - .NET, iOS, Databinding (Android), Angular (I think)
5. What’s Up With That “Clean” Stuff? • Uncle Bob - Clean Code • Uncle Bob - Clean Architecture • Martin Fowler… Image: Fernando Cejas - Clean Architecture
6. Clean vision of UI “A good architecture hangs the UI off the side like an appendix. That makes it easy to remove when it gets inflamed.” - Uncle Bob
7. Will It Blend (On Android?)
8. Clean in the Android World • It won’t blend THAT easily! • Everything extends Context • Everything else *requires* Context • “God” object • UI - first design
9. Ingredients
10. Model Presenter View userUpdatedBasket(item) showNewPrice(price) updateBasket(item) basketUpdated(price)
11. Model Presenter View userUpdatedBasket(item) showNewPrice(price) updateBasket(item) basketUpdated(price) Android Pure Java
12. Model Presenter View userUpdatedBasket(item) showNewPrice(price) updateBasket(item) basketUpdated(price) Android Pure Java Filesystem SharedPrefs Sensors … injected Android dependencies +
13. Layers in the real world /* and code samples! */
14. Model Layer • Does things • Business logic happens here • Handles outward facing APIs, persistence, sensors • Wraps com.android.* -
15. Wrapper - interface LocationWrapper { void requestLocation(…); } class LocationWrapperImpl implements LocationWrapper { GoogleApiClient apiClient; @Override void requestLocation(…){ //setup callbacks etc… LocationServices.FusedLocationApi.getLastLocation( apiClient); } }
16. Presenter Layer • The “glue” between the “M” and the “V” • View tells the presenter what happened • Tells the view what to do • goes to model for data
17. Presenter - Interface • View initialises it - to keep reference • Here’s where the memory leaks happen (if you’re not careful) interface BasketPresenter { void initialise(BasketView view); void itemQuantityChanged(BasketItem basketItem); void viewDestroyed(); }
18. Clean presenter implementation • Model accessed via interactors interface Interactor<T> { void performAction<T action>(InteractionCallback<T> actionCallback); } class CleanBasketPresenterImpl implements BasketPresenter { @Override void initialise(BasketView view){ basketView = view; } @Override void itemQuantityChanged(BasketItem basketItem){ updateItemQuantityInteractor.performAction(basketItem); } }
19. “Clean-ish” presenter implementation • Presenter directly accesses the model • + less classes • - more coupling class CleanishBasketPresenterImpl implements BasketPresenter { @Override void initialise(BasketView view){ basketView = view; } @Override void itemQuantityChanged(BasketItem basketItem){ basketAPI.updateItemQuantity(basketItem); } }
20. View Layer • A view is a View is an Activity • Keep the com.android.* here • Tells presenter what action has occurred • Knows how to show data • Handles navigation to other activities
21. Views and business logic • Just no. • Keep it in presenter…. • (if you must)
22. View - Interface interface BasketView { void showItems(List<BasketItem> basketItems); void update(BasketItem basketItem); void proceedToCheckout(); }
23. “keep the com.android* here” • coupled to the framework • face it - unavoidable • hard to test - need for UI testing class BasketActivity extends Activity implements BasketView { BasketPresenter presenter; //code
24. “tells the presenter what action has occurred” • Delegates on onClick, onDestroy, onResume to presenter • Translates android bits to pure java OnClickListener addToBasketListener = new OnClickListener { @Override public void onClick(View v){ presenter.itemQuantityChanged(basketItemWithNewQuantity); } }
25. “knows how to show it” • Display logic only in view • Both view and presenter understand data objects @Override void update(BasketItem basketItem){ basketViewsList.getView(basketItem.id).setData(basketItem); }
26. “handles navigation to other activities" • Intent creation needs Context • Intent dispatch needs (Activity) Context • Can use builder pattern to construct intents (with data) @Override void proceedToCheckout(){ startActivity(CheckoutActivity.buildIntent(this, basketItems)); }
27. Tools For The Win
28. Libraries to make life easier • Retrofit - REST made easy • Dagger - dependency injection • ButterKnife - view binding & easier listeners # • Otto / EventBus -
29. MVP Libraries to make life easier • There are many: Mosby, Nucleus, … • Make conventions easier • Handle presenter lifecycle for you
30. MVP not your cuppa? • MVVM - Model-View-ViewModel (like .NET) • Android DataBinding library to the rescue :) • XML galore! • http://developer.android.com/tools/data-binding/guide.html
31. Sugar, Spice (and something nice) • Testability comes free cheap • (half of the thing is core java anyway) • RxJava friendly
32. Tired of T-Shirt Weather in December? • M&S Digital is hiring (in London) • Mobile, backend, frontend, APIs, you name it! • http://www.mandsdigital.com/careers
33. Fin / Q&A? @zmarkan github.com/zmarkan www.spacecowboyrocketcompany.com zan@markan.me /r/androiddev, androidchat.co (slack) - zmarkan
34. Links - architecture • Code samples in one uncompilable Gist • https://blog.8thlight.com/uncle-bob/2012/08/13/the-clean-architecture.html • https://vimeo.com/43612849 (clean architecture - talk) • http://fernandocejas.com/2014/09/03/architecting-android-the-clean-way/ • http://antonioleiva.com/mvp-android/ • https://github.com/android10/Android-CleanArchitecture • https://github.com/rallat/EffectiveAndroid • Fragmented Podcast - The Fowler Road to Clean Architecture
35. Links - Tools • http://square.github.io/retrofit/ - Retrofit • http://square.github.io/dagger/ - Dagger 1 • http://google.github.io/dagger/ - Dagger 2 • http://jakewharton.github.io/butterknife/ - Butterknife • http://square.github.io/otto/ - Otto • http://hannesdorfmann.com/mosby/ - Mosby • https://github.com/konmik/nucleus - Nucleus • https://github.com/ReactiveX/RxJava - RxJava • https://github.com/ReactiveX/RxAndroid - RxAndroid