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EFFECTIVE ANDROID ARCHITECTURE

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Hi, I am Richa

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EFFECTIVE ANDROID ARCHITECTURE

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Who all has ever used MVC?

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MVC

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MVP ? MVC ? MVVM ?

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MODEL VIEW CONTROLLER Interact with DB Render Model Handle view events Update model Invoke next UI Table of Responsibilities

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Mobile Web Desktop

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MODEL VIEW CONTROLLER Interact with DB Render Model Handle view events Interact with network Manage view state Update model Navigation Interact with system components Handle system events Update view on 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 Interact with DB Render Model Handle view events Interact with network Manage view state Update model Navigation Interact with system components Handle system events Update view on system events

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Interactor?

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JUnit + Mocking

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MODEL VIEW CONTROLLER INTERACTOR Retrieve data from DB Render Model Handle view events Interact with external entities Retrieve data from network Manage view state Navigation Forward system events to view Forward model updates to view

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View Model ?

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JUnit + Mocking Android + Mocking Espresso + Mocking

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MODEL VIEW CONTROLLER INTERACTOR VIEW MODEL Retrieve data from Network Render View Model Handle view events Interact with external entities View state / behavior Retrieve data from network Navigation Update view state

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Presenter ?

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MODEL VIEW PRESENTER INTERACTOR VIEW MODEL Retrieve data from DB Render View Model Handle view events Interact with external entities View state / behavior Retrieve data from network Navigation Update view state

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Espresso + Mocking JUnit + Mocking JUnit + Mocking Android + Mocking Data Source

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ENTITIES VIEW PRESENTER INTERACTOR VIEW MODEL Get data from Data Sources Render View Model Handle view events Interact with external entities View state / behavior Navigation Update view state

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FlowController ?

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Android + Mocks

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ENTITIES VIEW PRESENTER INTERACTOR VIEW MODEL FLOW CONTROLLER Get data from Data Sources Render View Model Handle view events Update view state Interact with external entities View state / behavior Navigation

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Apply Dependency Inversion

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S ingle Responsibility Principle O pen/Closed Principle L iskov Substitution Principle I nterface Segregation Principle D ependency Inversion Principle

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Architecture is about Intents not Frameworks - Uncle Bob

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Implementation in Practice

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Activity Video Module Activity Quiz Module Navigation Main Activity Shell App Catalog Activity Catalog Module url Intent Intent Register with url Modules

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Deep links Shell App Video Activity Video Module Catalog Activity Catalog Module register register url Intent Intent

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ViewModels Save/Restore View Models Presenter Retainable Fragments Parcelables onSaveInstanceState onSaveInstanceState

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Chain of Responsibility View Presenter Interactor Network Persistence •Result •Error

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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 ~ 7 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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Code Demo - Sample app

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

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Classes • MainActivity • CatalogFlowController • CatalogActivity • CatalogPresenter • CatalogViewModel • CatalogInteractor

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MainActivity void onCreate() { CatalogFlowController.getInstance() .launchCatalogActivity(); }

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CatalogFlowController 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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CatalogPresenter void loadCatalog() { interactor.loadCourses() .subscribe(new Action1<>() { @Override public void call(List courses) { // action } }); }

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CatalogPresenter void subscribeToUpdates(Action1 a) { viewModel.subscribeToUpdates(a); } void unsubscribeToUpdates() { viewModel.unsubscribeToUpdates(); }

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CatalogViewModel public final BehaviorSubject catalog = BehaviorSubject.create(); public void subscribeToCatalog(Action1 action) { catalog.subscribe(action); } public void unsubscribeToCatalog() { catalog.unsubscribe(); }

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

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Coursera is hiring!

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Questions ?

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@richa123 rkhandelwal@coursera.org richk in/richak Thank You