Android Architecture - Speaker Deck

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Effective Android Architecture Richa Khandelwal Growth/Android/Front-End Engineer at Coursera

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▪ Challenges ▪ Finding the right architecture fit ▪ Validation ▪ Practice makes perfect! ▪ Demo and Samples ▪ Cons ▪ Key Takeaways Structure of the talk

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Available on Google Play Store Place your screenshot here Android App 1,825+ COURSES 18M+ LEARNERS 141+ PARTNERS

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109% increase in mobile usage since last year 24 % use mobile only 40 % use mobile and desktop

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Over 500k (and growing) new learners join Coursera every month

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Cross team Tightly aligned, loosely coupled Faster MVPs Learn fast, fail fast Network Speeds Edge, 2G, Spotty

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Who all has ever used MVC?

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MVC

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Where to Begin

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MVP ? MVC ? MVVM ? VIPER ?

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MODEL VIEW CONTROLLER Manage application data Render model Handle view events Interact with model Invoke next UI Table of Responsibilities

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Mobile Web Desktop

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MODEL VIEW CONTROLLER Manage data from network Render model Handle view events Manage data from local storage Manage view state Interact with model Manage model consistency Navigation Interact with system components Interact with system events Update view on model changes or system events

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Model public class CourseModel { Course getFromDatabase() { // fetch from db, or local cache } Course getFromNetwork() { // fetch from apis, cache when possible } }

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View public class ExpandableCourseListActivity { void onSaveInstanceState(Bundle b) { // save all expanded states } }

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Controller void onClick() {} void onModelUpdated() {} void onNewNotification() {} void onLocationUpdated(Location loc) {} void takePhoto(Activity context) {} void launchView(Activity context ) {}

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MVC ??

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MODEL VIEW CONTROLLER Manage data from local storage Render model Handle view events Manage data from network Manage view state Interact with model Manage model consistency Navigation Interact with system components Interact with system events Update view on model changes or system events

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Interactor?

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MODEL VIEW CONTROLLER INTERACTOR Manage data from local storage Render view data Handle view events Interact with external entities Manage data from network Manage view data/ updates Navigation Manage model consistency Forward view data updates to view

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View Model ?

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MODEL VIEW CONTROLLER INTERACTOR VIEW MODEL Manage data from local storage Render view model Handle view events Interact with external entities Manage view data Manage data from network Navigation Manage model consistency Manage view model

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Presenter ?

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MODEL VIEW PRESENTER INTERACTOR VIEW MODEL Manage data from local storage Render view model Handle view events Interact with external entities Manage view data Manage data from network Navigation Manage model consistency Manage view model

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Data Source

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ENTITIES VIEW PRESENTER INTERACTOR VIEW MODEL Represent model objects Render view model Handle view events Interact with external entities Manage view data Navigation Manage view model

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FlowController ?

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coursera-android://app/

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ENTITIES VIEW PRESENTER INTERACTOR VIEW MODEL FLOW CONTROLLER Represent model objects Render view model Manage view events and view model Interact with external entities Manage view data Navigation

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Apply Dependency Inversion

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Data Source

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Espresso + Mocking JUnit + Mocking Android/ JUnit + Mocking Android/ JUnit + Mocks Data Source

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@AutoValue @AutoParcel https://github.com/google/auto V2 - and beyond ▪ Good developers write code, great developers generate! ▪ When code is generated, why write tests? ▪ Use code generation and annotation processing heavily. ▹ Custom annotation processors - Data source policies, Routing, Model, Event Tracking generation. https://github.com/rharter/auto-value-gson

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V2 - and beyond ▪ Data Source layer can evolve separately from the rest of the application. ▪ Load all data on critical path. ▪ Leverage common interfaces like `onLoad` in the Presenters to prefetch data on critical path of user experience.

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Code Demo - Sample app

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Source Code https://github.com/richk/ CourseraDemoApp

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Classes • MainActivity • FlowController • CatalogActivity • CatalogPresenter • CatalogViewModel • CatalogInteractor

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MainActivity void onCreate() { FlowController.getInstance() .launchCatalogActivity(this); }

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FlowController void launchCatalogActivity(Context c) { Intent intent = …; c.startActivity(intent) }

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CatalogActivity CatalogPresenter presenter; void onCreate() { presenter = new CatalogPresenter(this); }

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CatalogActivity void onResume() { Action1 action = ; presenter.subscribeToUpdates(action) }

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CatalogActivity void onPause() { presenter.unsubscribeToUpdates(); }

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CatalogPresenter CatalogInteractor interactor; CatalogPresenter(Context c) { viewModel = new CatalogViewModel(); interactor = new CatalogInteractor(c); loadCatalog(); }

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CatalogViewModel // Parcelable public final Catalog catalog = new Catalog();

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CatalogInteractor Context mContext; public CatalogInteractor(Context context) { mContext = context; } public Observable loadCatalog() { return catalogDataSource.loadCatalog(mContext.getApplication( )); }

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CatalogPresenter void loadCatalog() { interactor.loadCourses().observeOn(AndroidSchedulers.mainThread()) .subscribe(new Action1<>() { @Override public void call(List courses) { // update the view model } }); }

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The Cons

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Dealing with context Presenter(Context context) Interactor(Context context) NetworkClient(Context context) PersistenceClient(Context context) context.getSystemService(“SERVICE”) context.startActivity(intent) context.startActivityForResult(intent)

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Tedium ~ 4 classes per feature/module

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Adopting as a team Educating new hires

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Key Takeaways

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Ship the latest ideas

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Refactor or Not?

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Validate

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Iterate, Iterate, Iterate

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We Are Hiring! Apply

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@richa123 [email protected] richk in/richak Thank You

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References ▪ Android dialogs - https://www.youtube.com/watch?v=VTaguVtvuYI ▪ https://github.com/square/okhttp ▪ https://github.com/square/retrofit ▪ http://google.github.io/dagger/ ▪ https://github.com/ReactiveX/RxAndroid ▪ http://360andev.com/sessions/100-libraries-i-wish-i-knew-about-when-i- started/ ▪http://360andev.com/sessions/100-eliminateboilerplate/ ▪ https://github.com/googlesamples/android-architecture ▪ http://360andev.com/sessions/100-intro-to-rxjava/

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Questions ?