![HOW RXJAVA?
CREATING OBSERVABLES: FROM()
Observable.from(Arrays.asList(1, 2, 3));
Observable.from(new Integer[]{1, 2, 3});](https://image.slidesharecdn.com/intro-to-rxjava-160225071825/85/Intro-to-RxJava-RxAndroid-GDG-Munich-Android-13-320.jpg)
Intro to RxJava/RxAndroid - GDG Munich Android
- 1. INTRO TO RXJAVA & RXANDROID Egor Andreevici
- 4. “RXJAVA IS A JAVA VM IMPLEMENTATION OF REACTIVEX (REACTIVE EXTENSIONS): A LIBRARY FOR COMPOSING ASYNCHRONOUS AND EVENT-BASED PROGRAMS BY USING OBSERVABLE SEQUENCES.” RxJava Wiki WHAT IS RXJAVA?
- 5. WHAT IS RXJAVA? OBSERVABLES (AND MARBLE DIAGRAMS)
- 6. WHAT IS RXJAVA? PROGRAM STRUCTURE subscription = Observable .create(…) .transform(…) .subscribe(...);
- 7. HOW RXJAVA?
- 8. HOW RXJAVA? THE HIGH LEVEL PLAN ▸ Create an Observable ▸ Manipulate data using operators ▸ Subscribe and consume ▸ Profit!
- 9. HOW RXJAVA? CREATING OBSERVABLES: CREATE() Observable.create(subscriber -> { try { for (int value = 1; value <= 3; value++) { subscriber.onNext(value); } subscriber.onCompleted(); } catch (Throwable t) { subscriber.onError(t); } });
- 10. HOW RXJAVA? THE OBSERVER INTERFACE public interface Observer<T> { void onCompleted(); void onError(Throwable e); void onNext(T t); }
- 11. HOW RXJAVA? THE NOTIFICATIONS CONTRACT ▸ Zero or more onNext() notifications ▸ Either onCompleted() or onError(), not both! ▸ Nothing more! ▸ May never terminate ▸ May never call onCompleted() ▸ All notifications must be issued serially
- 12. HOW RXJAVA? CREATING OBSERVABLES: JUST() Observable.just(1); Observable.just(1, 2); Observable.just(1, 2, 3); . . . Observable.just(1, … , 9);
- 13. HOW RXJAVA? CREATING OBSERVABLES: FROM() Observable.from(Arrays.asList(1, 2, 3)); Observable.from(new Integer[]{1, 2, 3});
- 14. HOW RXJAVA? CREATING OBSERVABLES: MISC Observable.empty(); Observable.error(t); Observable.never();
- 15. HOW RXJAVA? Observable.create(subscriber -> { try { for (int i = 0; i < 10000; i++) { T value = longRunningNetworkRequest(); subscriber.onNext(value); } subscriber.onCompleted(); } catch (Throwable t) { subscriber.onError(t); } }); CAVEATS: HANDLING UNSUBSCRIBING
- 16. HOW RXJAVA? SUBSCRIPTION INTERFACE public interface Subscription { void unsubscribe(); boolean isUnsubscribed(); }
- 17. HOW RXJAVA? CAVEATS: HANDLING UNSUBSCRIBING Observable.create(subscriber -> { try { for (int i = 0; i < 10000; i++) { if (subscriber.isUnsubscribed()) { return; } T value = longRunningNetworkRequest(); subscriber.onNext(value); } subscriber.onCompleted(); } catch (Throwable t) { subscriber.onError(t); } });
- 18. HOW RXJAVA? OPERATORS ▸ Transformational ▸ map() ▸ flatMap() ▸ concatMap() ▸ Filtering ▸ filter() ▸ take() ▸ skip() ▸ Combining ▸ merge() ▸ zip() ▸ combineLatest() AND MANY MORE…
- 23. HOW RXJAVA? SUBSCRIBING TO OBSERVABLES .subscribe( value -> renderValue(value), error -> renderError(error), () -> Log.d(LOGTAG, "Done!"));
- 24. HOW RXJAVA? MULTITHREADING: OPERATORS Observable<T> observeOn(Scheduler scheduler) {} Observable<T> subscribeOn(Scheduler scheduler) {}
- 26. HOW RXJAVA? TESTING: BLOCKING OBSERVABLES @Test public void testingWithBlockingObservable() { Observable<Integer> intObservable = Observable.just(1, 2, 3); BlockingObservable<Integer> blocking = intObservable.toBlocking(); assertThat(blocking.first()).isEqualTo(1); assertThat(blocking.last()).isEqualTo(3); blocking.getIterator(); blocking.toIterable(); }
- 27. HOW RXJAVA? TESTING: TESTSUBSCRIBER @Test public void testingWithTestSubscriber() { Observable<Integer> intObservable = Observable.just(1, 2, 3); TestSubscriber<Integer> testSubscriber = TestSubscriber.create(); intObservable.subscribe(testSubscriber); testSubscriber.assertValues(1, 2, 3); testSubscriber.assertNoErrors(); testSubscriber.assertCompleted(); }
- 28. HOW RXJAVA? DEBUGGING: SIDE EFFECTS Observable.just(1, 2, 3) .doOnNext(next -> append("Before filter: " + next)) .filter(value -> value % 2 == 0) .doOnNext(next -> append("After filter: " + next)) .subscribe(...);
- 30. RXJAVA ON ANDROID RXANDROID ▸ Super tiny ▸ AndroidSchedulers.mainThread() ▸ HandlerScheduler.from(Handler)
- 31. RXJAVA ON ANDROID RXBINDING ▸ RxJava binding APIs for Android's UI widgets ▸ RxView.clicks(…), RxView.enabled(…) etc. ▸ RxTextView.textChanges(…)
- 32. RXJAVA ON ANDROID RXLIFECYCLE ▸ Lifecycle handling APIs for Android apps using RxJava ▸ .compose(RxLifecycle.bindActivity(lifecycle)) ▸ RxActivity, RxFragment ▸ .compose(bindToLifecycle())
- 33. RXJAVA ON ANDROID RETROFIT: THE UGLY @Override public void onActivityCreated(Bundle savedInstanceState) { super.onActivityCreated(savedInstanceState); GithubApiClient client = createGithubApiClient(); try { List<Repo> repos = client.getRepos().execute().body(); // render repos } catch (IOException e) { // handle } }
- 34. RXJAVA ON ANDROID RETROFIT: THE BAD @Override public void onActivityCreated(Bundle savedInstanceState) { super.onActivityCreated(savedInstanceState); GithubApiClient client = createGithubApiClient(); client.getRepos().enqueue(new Callback<List<Repo>>() { @Override public void onResponse(Call<List<Repo>> call, Response<List<Repo>> response) { // render repos } @Override public void onFailure(Call<List<Repo>> call, Throwable t) { // handle } }); }
- 35. RXJAVA ON ANDROID RETROFIT: THE GOOD @Override public void onActivityCreated(Bundle savedInstanceState) { super.onActivityCreated(savedInstanceState); GithubApiClient client = createGithubApiClient(); subscription = client.getRepos() .subscribeOn(Schedulers.io()) .observeOn(AndroidSchedulers.mainThread()) .subscribe( repos -> renderRepos(repos), error -> handleError(error)); }
- 36. WHY RXJAVA?
- 37. WHY RXJAVA? WHY RXJAVA? ▸ Set of powerful operators ▸ Easy threading ▸ Explicit error handling ▸ Testable ▸ Lots of perks specific to Android
- 38. DEMO TIME!
- 39. THANK YOU! Egor Andreevici blog.egorand.me · @EgorAnd · +EgorAndreevich