Moderne App-Architektur mit Dagger2 und RxJava
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The document discusses modern app architecture using Dagger 2 for dependency injection and RxJava for asynchronous data flows. It covers dependency injection and how Dagger 2 avoids reflection for faster performance. It also discusses the model-view-presenter pattern to separate business logic from display logic. Finally, it explains how RxJava uses observables and observers to implement asynchronous data streams and how this avoids callback hell and allows pushing data instead of polling.
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Moderne App-Architektur mit Dagger2 und RxJava
- 1. •Moderne App-Architektur mit Dagger2 und RxJava • code.talks 2015 Martin Breuer http://www.gedankensuppe.de/hamburg
- 2. Dominik Helleberg +DominikHelleberg Mobile Application Development Tools Android / Embedded
- 3. Angelo Rüggeberg +AngeloRüggeberg Google Developer Group, Munich | Lead Mobile Application Development Android Enthusiast Since Cupcake (Version 1.5)
- 6. App Architektur Themen • Dependency Injection • MV(i)P • RxJava
- 7. Dependency Injection • Your class get’s what it needs (Dependenciescome to you) • You have no idea where they come from • A well known pattern • Everyone uses it (more or less) App Architektur Dependency Injection
- 8. Dependency Injection • It’s common sense on the server side • There are already frameworks out there: –Spring DI –Google Guice –Pico Container –... App Architektur Dependency Injection
- 9. Dependency Injection - Android Now what about android? • Mobile (limited ressources) • App Startup time does really matter • Reflection is slow • App Size + method count does really matter App Architektur Dependency Injection
- 10. Dagger 2 Why another Framework? • no reflection at all • Based on Dagger1 • Proposed + Implemented by the Java Core Team (Google) • Code generation (As if you would write it) App Architektur Dependency Injection
- 11. Dagger 2 - Basics @Modules / @Provides • Provide Dependenciesto @Inject • Requests for Dependencies @Components • Public API, the Bridge between Modules and Injects and some more... App Architektur Dependency Injection
- 12. Dagger2 TwitterTimeline (interface) TwitterTimeline RestAdapter MockTwitter Timeline HTTPClient App Architektur Dependency Injection
- 14. @Singleton @Component (modules = {ApplicationModule.class, NetworkingModule.class}) public interface ApplicationComponent { MVPComponent plus();; } App Architektur Dependency Injection
- 15. @Module public class NetworkingModule { @Provides @Singleton TwitterTimeline provideTwitterTimeline(RestAdapter restAdapter) { return restAdapter.create(TwitterTimeline.class);; } @Provides @Singleton public RestAdapter provideRestAdapter(SigningOkClient client) { return TwitterApiAdapter.getInstance(client);; } App Architektur Dependency Injection
- 17. @Module public class MockNetworkingModule extends NetworkingModule { @Provides @Singleton TwitterTimeline provideTwitterTimeline() { return new MockTwitterTimeline();; } } App Architektur Dependency Injection
- 18. Dagger2 • DI is a good thing to have • steep learning curve • Sometimes hard to get hold on component references • Still under active development • Enforces structured code • Code generation is a good thing App Architektur Dependency Injection
- 19. Model View Presenter (MViP) • Seperate Business Logic, Application Logic, Display Logic • Change independent parts without Issues • Easier to Test –Mock Network Modules etc. App Architektur MViP
- 20. MViP: Components • Model –Data that is represented –for example Tweets • View –The View Displaying the Data –can be Activity, Fragment, CustomView • Presenter –Logic –for example fetching Tweets from Network App Architektur MViP
- 23. App Architektur MViP Activity fetchFeed() updateFeed(List Feed) updateListitem(item) onTextChanged()
- 24. MViP: Model • The Data that is displayed to the User • Data used to do Interactions with the Presenter • Can be the same as the Models for Network Requests –Retrofit App Architektur MViP
- 25. public class Tweet { @JsonProperty("created_at") private String DateCreated;; @JsonProperty("id") private long Id;; @JsonProperty("text") private String Text;; @JsonProperty("user") private TwitterUser User;; } App Architektur MViP -‐ Model
- 26. • Interface • Actual Display Unit Implements Interface –Fragment, Activity, Custom View, whatever… • Views should be dumb! –Only react to Actions • No Business Logic in here MVP: View App Architektur MViP
- 27. public interface TwitterTimelineView { void showLoading();; void hideLoading();; void showFeed(List<Tweet> messages);; void showError(String errorMessage);; } App Architektur MViP -‐ View
- 28. class HashtagFeedActivity extends BaseActivity implements TwitterTimelineView { @Override public void showLoading() { … } @Override public void hideLoading() { … } @Override public void showFeed(List<Tweet> messages) { … } @Override public void showError(String errorMessage) { … } App Architektur MViP -‐ View
- 29. class HashtagFeedActivity extends BaseActivity implements TwitterTimelineView { @Override public void showLoading() { … } @Override public void hideLoading() { … } @Override public void showFeed(List<Tweet> messages) { … } @Override public void showError(String errorMessage) { … } App Architektur MViP -‐ View
- 30. class HashtagFeedActivity extends BaseActivity implements TwitterTimelineView { @Override public void showLoading() { … } @Override public void hideLoading() { … } @Override public void showFeed(List<Tweet> messages) { … } @Override public void showError(String errorMessage) { … } App Architektur MViP -‐ View
- 31. Presenter • Interface • Binds to the View • Business Logic in here App Architektur MViP
- 32. public interface Presenter<T> { void onDestroy();; void bindView(T view);; void unbindView();; } App Architektur MViP -‐ Presenter
- 33. public interface TwitterHashtagTimelinePresenter extends Presenter<TwitterTimelineView>{ void bindSearchView(EditText textView);; void loadHashtagTimeline(String hashtag);; void goToDetails(Activity context, Tweet t);; } App Architektur MViP -‐ Presenter
- 34. public interface TwitterHashtagTimelinePresenter extends Presenter<TwitterTimelineView>{ void bindSearchView(EditText textView);; void loadHashtagTimeline(String hashtag);; void goToDetails(Activity context, Tweet t);; } App Architektur MViP -‐ Presenter
- 35. public class TwitterHashtagTimelinePresenterImpl implements TwitterHashtagTimelinePresenter { private TwitterTimelineView view;; @Override public void bindView(TwitterTimelineView view) { this.view = view;; } @Override public void loadHashtagTimeline(String hashtag) { … Do Network Request ... } App Architektur MViP -‐ Presenter
- 36. public class TwitterHashtagTimelinePresenterImpl implements TwitterHashtagTimelinePresenter { private TwitterTimelineView view;; @Override public void bindView(TwitterTimelineView view) { this.view = view;; } @Override public void loadHashtagTimeline(String hashtag) { … Do Network Request ... } App Architektur MViP -‐ Presenter
- 37. public class TwitterHashtagTimelinePresenterImpl implements TwitterHashtagTimelinePresenter { private TwitterTimelineView view;; @Override public void bindView(TwitterTimelineView view) { this.view = view;; } @Override public void loadHashtagTimeline(String hashtag) { … Do Network Request ... } App Architektur MViP -‐ Presenter
- 38. public class TwitterHashtagTimelinePresenterImpl implements TwitterHashtagTimelinePresenter { private TwitterTimelineView view;; @Override public void bindView(TwitterTimelineView view) { this.view = view;; } @Override public void loadHashtagTimeline(String hashtag) { … Do Network Request ... } App Architektur MViP -‐ Presenter
- 39. @Override public void loadHashtagTimeline(String hashtag) { view.showLoading();; List<Tweet> tweets = interactor.loadHashtagTweets(hashtag);; view.showTweets(tweets);; view.hideLoading();; } App Architektur MViP -‐ Presenter
- 40. @Override public void loadHashtagTimeline(String hashtag) { view.showLoading();; List<Tweet> tweets = interactor.loadHashtagTweets(hashtag);; view.showTweets(tweets);; view.hideLoading();; } App Architektur MViP -‐ Presenter
- 41. @Override public void loadHashtagTimeline(String hashtag) { view.showLoading();; List<Tweet> tweets = interactor.loadHashtagTweets(hashtag);; view.showTweets(tweets);; view.hideLoading();; } App Architektur MViP -‐ Presenter
- 42. Interactor? • Do not bloat up Presenters! • Interactors are used for doing things –Fetching Stuff from the network –Fetching Stuff from Disk • Interface again! App Architektur MViP -‐ interactor
- 43. public interface TwitterTimelineInteractor { void loadUserTweets(Observer<? super List<Tweet>> observer, String username);; void loadHashtagTweets(Observer<? super List<Tweet>> observer, String hastag);; Observable<List<Tweet>> loadHashtagTweets(String hashtag);; void pollHashtagTweets(Observer<? super List<Tweet>> observer, String hashtag);; } App Architektur MViP -‐ interactor
- 44. public class TwitterTimelineInteractorImpl implements TwitterTimelineInteractor { TwitterTimeline twitterTimeline;; @Override public void loadUserTweets(Observer<? super List<Tweet>> observer, String username) { twitterTimeline .getUserTimeline(username) .subscribeOn(Schedulers.io()) .observeOn(AndroidSchedulers.mainThread()) .subscribe(observer);; } App Architektur MViP -‐ interactor
- 46. Why? • Push don’t Poll! –do not stress the UI –do not stress the Application • Avoid Lifecycle Problems • Avoid the Callback Hell • Death to: –Boilerplate Code –AsyncTasks, Timertasks, Loaders, etc... App Architektur RXJava
- 47. RX: What? • Programming Paradigm based on asynchronous Data Flow • Idea from the late 90s • Erik Meijer (Microsoft) developed first RX extension for .NET • Adapted by many Programming languages App Architektur RXJava
- 48. RX: What? • Ported to JVM by Ben Christensen and Jafar Husain (Netflix) –Java, Closure, Groovy, Scala, etc etc…. • RXJava -> RXAndroid • The Observer pattern done right. App Architektur RXJava http://reactivex.io/
- 50. RXAndroid: How? • Producing Entities: –Observables –Subjects • Consuming Entities: –Observers –Subscribers • Consuming Entities subscribe to Producing Entities App Architektur RXJava
- 51. RXAndroid: Setup compile 'io.reactivex:rxandroid:1.0.1' //optional compile 'io.reactivex:rxjava:1.0.14' App Architektur RXJava
- 52. Observers Lifecycle: –onNext(T): • gets called when new Data is emited with the Data –onCompleted(): • gets called when the Sequence is done –onError(Throwable): • gets called when an Error occured App Architektur RXJava
- 53. Observables • Sequence that emits data –can emit more than once • Lives as long as there is work to do • Observers subscribe to an Observable • When there is no Subscriber, the Observable emits the data nowhere App Architektur RXJava
- 54. Sequence Example Observable Emits Something every Second App Architektur RXJava
- 55. Sequence Example Observable Observer Subscribe Unsubscribe onNext(T);; App Architektur RXJava
- 56. Observable<Long> interval = Observable .interval(1, TimeUnit.SECONDS);; App Architektur RXJava
- 57. interval.subscribe(new Observer<Long>() { @Override public void onCompleted() { Timber.d("onCompleted");; } @Override public void onError(Throwable e) { Timber.e(e, e.getMessage());; } @Override public void onNext(Long aLong) { Timber.d("Tick: " + aLong.toString());; App Architektur RXJava
- 58. Transforming the Data • We do not want a Long as result, we want a String • map() –gets the Long value –returns a String value • Chainable! –map().map().map().map().............map() App Architektur RXJava
- 59. Observable<String> interval = Observable .interval(1, TimeUnit.SECONDS) .map(new Func1<Long, String>() { @Override public String call(Long aLong) { return "Tick: " + aLong.toString();; } });; App Architektur RXJava
- 60. Observable<String> interval = Observable .interval(1, TimeUnit.SECONDS) .map(new Func1<Long, String>() { @Override public String call(Long aLong) { return "Tick: " + aLong.toString();; } });; App Architektur RXJava
- 61. Observable<String> interval = Observable .interval(1, TimeUnit.SECONDS) .map(new Func1<Long, String>() { @Override public String call(Long aLong) { return "Tick: " + aLong.toString();; } });; Returns Long App Architektur RXJava
- 62. Observable<String> interval = Observable .interval(1, TimeUnit.SECONDS) .map(new Func1<Long, String>() { @Override public String call(Long aLong) { return "Tick: " + aLong.toString();; } });; Takes the Long Transforms the Data and returns a String App Architektur RXJava
- 63. Hello Again Boilerplatecode • new Func1<T, T>() { public T call(t t2) { … } for every mapping will turn the code really unreadable and bloated • Lambda to the Rescue! –retrolambda for android & gradle –https://github.com/evant/gradle-retrolambda App Architektur RXJava
- 64. Observable<String> interval = Observable .interval(1, TimeUnit.SECONDS) .map(new Func1<Long, String>() { @Override public String call(Long aLong) { return "Tick: " + aLong.toString();; } });; App Architektur RXJava
- 65. Observable<String> interval = Observable .interval(1, TimeUnit.SECONDS) .map(aLong -> "Tick: " + aLong.toString());; App Architektur RXJava
- 66. Observable<String> interval = Observable .interval(1, TimeUnit.SECONDS) .map(aLong -> aLong.toString()) .map(string -> "Tick: " + string);; App Architektur RXJava
- 67. Combining Observables • Prevent Callback hell • Easy to Synchronize for async Operations • Running 2 Network Calls and combine the Results • Combine onTextChanged events from two fields • etc. • .zip(), combineLatest() App Architektur RXJava
- 68. Observable.combineLatest( WidgetObservable.text(txt1, false), WidgetObservable.text(txt2, false), (event1, event2) -> event1.text().toString() + event2.text().toString() ).subscribe(combined -> { Timber.d(combined);; });; App Architektur RXJava
- 69. Observable.combineLatest( WidgetObservable.text(txt1, false), WidgetObservable.text(txt2, false), (event1, event2) -> event1.text().toString() + event2.text().toString() ).subscribe(combined -> { Timber.d(combined);; });; App Architektur RXJava
- 70. Observable.combineLatest( WidgetObservable.text(txt1, false), WidgetObservable.text(txt2, false), (event1, event2) -> event1.text().toString() + event2.text().toString() ).subscribe(combined -> { Timber.d(combined);; });; App Architektur RXJava
- 71. Observable.combineLatest( WidgetObservable.text(txt1, false), WidgetObservable.text(txt2, false), (event1, event2) -> event1.text().toString() + event2.text().toString() ).subscribe(combined -> { Timber.d(combined);; });; App Architektur RXJava
- 72. Observable.combineLatest( WidgetObservable.text(txt1, false), WidgetObservable.text(txt2, false), (event1, event2) -> event1.text().toString() + event2.text().toString() ).subscribe(combined -> { Timber.d(combined);; });; App Architektur RXJava
- 73. Example: Livesearch • Retrieve the user Input from a EditText when text changes –only after nothing changes for 600 ms • Add # infront of the input to do a hastag search • Call the network (via Retrofit) –returns StatusesResponse Object • Transform to List<Tweets> • Show Tweets in view App Architektur RXJava
- 76. textChangeObservable .observeOn(AndroidSchedulers.mainThread()) .map(onTextChangeEvent -> onTextChangeEvent.text().toString()) .map(searchText -> "#" + searchText)
- 77. textChangeObservable .observeOn(AndroidSchedulers.mainThread()) .map(onTextChangeEvent -> onTextChangeEvent.text().toString()) .map(searchText -> "#" + searchText) .subscribe( tag -> { Timber.d(tag);; loadHashtagTimeline(tag);; }
- 78. textChangeObservable .observeOn(AndroidSchedulers.mainThread()) .map(onTextChangeEvent -> onTextChangeEvent.text().toString()) .map(searchText -> "#" + searchText) .subscribe( tag -> { Timber.d(tag);; loadHashtagTimeline(tag);; }, e -> { Timber.e(e, e.getMessage());; view.showError(e.getMessage());; } );;
- 79. textChangeObservable .debounce(600, TimeUnit.MILLISECONDS) .observeOn(AndroidSchedulers.mainThread()) .map(onTextChangeEvent -> onTextChangeEvent.text().toString()) .map(searchText -> "#" + searchText) .subscribe( tag -> { Timber.d(tag);; loadHashtagTimeline(tag);; }, e -> { Timber.e(e, e.getMessage());; view.showError(e.getMessage());; } );;
- 80. Demo
- 81. Thank You!