Reactive programming on Android

Android Dev Saigon meet up #3
Twitter: @thanhbc1990
Github demo: github.com/thanhbc/popularmovies

Transcript

1. Reactive programming on Android Ban Chinh Thanh (@thanhbc1990) Prime Labo Co. VN Android developer
2. Ban Chính Thành • A Little ninja at PrimeLabo • Android developer for over 2 years Email:chinh.thanh@primelabo.com.vn Github: http://github.com/thanhbc
3. Let’s talk about RxJava!
4. RxJava is a library that let’s you represent anything as asynchronous data-stream (event stream) that can be create on any thread, functionally transformed, and consumed by everyone on any thread.
5. Represent anything that can be created on any thread and consumed on any thread as a data stream functionally transformed by everyone
6. wtf is he saying
7. Outline • RxJava introduction • Basic of RxJava • RxJava with Android
8. What is RxJava?
9. What is RxJava?
10. Reactive Extensions (Rx)
11. A library for composing asynchronous and event-based programs by using observable sequences.
12. https://github.com/ReactiveX/RxJava “RxJava is a Java VM implementation of Reactive Extensions”
13. Reactive • Asynchronous • Event streams • Reacting to change
14. Reactive programming : Programming with asynchronous event streams
15. Streams event1 event2 event3 “Events” can be anything
16. Events Click events Text change events Keyboard pressed events Network response events Sign in events … endless possibilities.
17. Taken from https://gist.github.com/staltz/868e7e9bc2a7b8c1f754
18. “We can represent anything as a stream”
19. Observer Pattern
20. Observer Pattern public interface Observer<T>{
 public abstract void onCompleted();
 public abstract void onError(Throwable e);
 public abstract void onNext(T t);
 } public interface Observable<T>{
 public Subscription subscribe(Observer<? super T> subscriber);
 } Observable Observer subscribe emit items
21. An Observable emits items. A Subscriber/Observer consumes those items A Subscription control the stream
22. Example Observable Scheduler Operators Observer/Subscriber
23. Observable http://reactivex.io/RxJava/javadoc/rx/Observable.html
24. Observables are the source of data
25. Create Observable • Observable.just() • Observable.from() • …etc.
26. Observable.just • Convert an object or several objects into an Observable Observable.just("Hello Guys!")
27. Observer • Observer is the one who received in data • Observer and Observable connected through subscribe method - Subscriptions • Observer through subscribe to listen an Observable
28. Subscribe • Connect Observable and Observer • Need to be implemented Observer interface • onNext, onError, onComplete public final Subscription subscribe(final Action1<? super T> onNext, final Action1<Throwable> onError, final Action0 onComplete) {
 /*..*/ }
29. Observable.just("Hello Guys!").subscribe(new Action1<String>() {
 @Override
 public void call(String s) {
 Log.d(TAG, ">>>>>>>" + s + "<<<<<<<");
 }
 });
 
 Observable.just("Hello Guys!")
 .subscribe(new Action1<String>() {
 @Override
 public void call(String s) {
 Log.d(TAG, ">>>>>>>" + s + "<<<<<<<");
 }
 }, new Action1<Throwable>() {
 @Override
 public void call(Throwable throwable) {
 Log.d(TAG, ">>>>>>> Error, cant say hi to your guys <<<<<<<");
 }
 }, new Action0() {
 @Override
 public void call() {
 Log.d(TAG, ">>>>>>> Completed <<<<<<<");
 }
 }); Or just Out put: >>>>>>>Hello Guys!<<<<<<< >>>>>>> Completed <<<<<<< Out put: >>>>>>>Hello Guys!<<<<<<<
30. Observable.from • Convert an Iterable, a Future, or an Array into an Observable Observable.from(listOfInteger)
31. Observable.from List<Integer> integers = new ArrayList<>();
 integers.add(1);
 integers.add(2);
 integers.add(3);
 integers.add(4);
 integers.add(5);
 
 Observable.from(integers).subscribe(new Action1<Integer>() {
 @Override
 public void call(Integer integer) {
 Log.d(TAG, ">>>>>>> integer: " + integer);
 }
 }); Out put: >>>>>>> integer: 1 >>>>>>> integer: 2 >>>>>>> integer: 3 >>>>>>> integer: 4 >>>>>>> integer: 5
32. Control the stream with Subscriptions
33. Observable.subscribe() return a subscription
34. But…
35. But… Subscriptions leak memory Just 2 methods 1. isUnsubscribed() 2. unsubscribe()
36. Memory leak fix public void detachView() {
 if(searchResultSubscription != null && !searchResultSubscription.isUnsubscribed())
 searchResultSubscription.unsubscribe();
 }
37. “Hot” & “Cold” Observable • When an Observable emit datas? • Hot Observable • When it created • Cold Observable • When an observer subscribe
38. FRP: Event streams with functional methods
39. Operators are functions to manipulate streams
40. Operators • Creating Observables (ex: create, from, just, …) • Transforming Observables (ex: map, flatMap, …) • Filtering Observables • Combining Observables • ErrorHandling Operators • Observable Utility Operators • see example on http://rxmarbles.com & PlayStore available
41. Map Operator
42. Transform via Map Observable<DiscoverMovie> observable = service.getSearchResult(encodedQuery, TheMovieDBService.API_KEY);
 searchResultSubscription = observable
 .subscribeOn(Schedulers.io())
 .observeOn(AndroidSchedulers.mainThread()) 
 .subscribe(searchResultsSubscriber());
 .map(new Func1<DiscoverMovie, List<Result>>() {
 @Override
 public List<Result> call(DiscoverMovie searchResult) {
 return searchResult.results; // list of movies info
 }
 })
 DiscoverMovie transformed to List<Result>
43. Android?
44. compile 'io.reactivex:rxjava:1.1.0'
 compile 'io.reactivex:rxandroid:1.1.0'
45. Why? (Android) Main/UI Thread and background problem • Can’t do heavy tasks on UI • Can’t update view on background • AsyncTasks are bad • Handlers can leak
46. RxJava is synchronous by default.
47. Concurrency subscribeOn() - Thread to work on observeOn() - Thread to observe items on
48. Synchronous Observable.create(new Observable.OnSubscribe<String>() {
 @Override
 public void call(Subscriber<? super String> subscriber) {
 String threadID = String.valueOf(Thread.currentThread().getId());
 Log.d(TAG,"working on thread: " + threadID);
 subscriber.onNext("Android");
 subscriber.onNext("Meetup #3");
 subscriber.onCompleted();
 }
 })
 .subscribe(new Action1<String>() {
 @Override
 public void call(String s) {
 String threadID = String.valueOf(Thread.currentThread().getId());
 Log.d(TAG,"onNext on thread: " + threadID + );
 }
 }); Out put: working on thread: 1 onNext on thread: 1 -> Android onNext on thread: 1 -> Meetup #3
49. Asynchronous Observable.create(new Observable.OnSubscribe<String>() {
 @Override
 public void call(Subscriber<? super String> subscriber) {
 String threadID = String.valueOf(Thread.currentThread().getId());
 Log.d(TAG,"working on thread: " + threadID);
 subscriber.onNext("Android");
 subscriber.onNext("Meetup #3");
 subscriber.onCompleted();
 }
 })
 .observeOn(Schedulers.newThread())
 .subscribe(new Action1<String>() {
 @Override
 public void call(String s) {
 String threadID = String.valueOf(Thread.currentThread().getId());
 Log.d(TAG, "onNext on thread: " + threadID + " -> " + s);
 }
 }); Out put: working on thread: 1 onNext on thread: 525 -> Android onNext on thread: 525 -> Meetup #3
50. Asynchronous Observable.create(new Observable.OnSubscribe<String>() {
 @Override
 public void call(Subscriber<? super String> subscriber) {
 String threadID = String.valueOf(Thread.currentThread().getId());
 Log.d(TAG,"working on thread: " + threadID);
 subscriber.onNext("Android");
 subscriber.onNext("Meetup #3");
 subscriber.onCompleted();
 }
 })
 .observeOn(Schedulers.newThread())
 .subscribeOn(Schedulers.newThread())
 .subscribe(new Action1<String>() {
 @Override
 public void call(String s) {
 String threadID = String.valueOf(Thread.currentThread().getId());
 Log.d(TAG, "onNext on thread: " + threadID + " -> " + s);
 }
 }); Out put: working on thread: 529 onNext on thread: 532 -> Android onNext on thread: 532 -> Meetup #3
51. Let’s recap!
52. Represent anything that can be created on any thread and consumed on any thread as a data stream functionally transformed by everyone Observable<T> Scheduler Operators Subscriber<T> Scheduler
53. Useful links • Grokking RxJava by Dan Lew • ReactiveX / RxJava • reactivex.io • rxmarble
54. Questions?
55. We’re hiring! • Senior Android & iOS • Android & iOS developer • Java Programmer • VB6
56. THANK YOU! Twitter: @thanhbc1990 Personal email: thanhbc1990@gmail.com