The Beginner's Guide to RxJava

The Beginner's Guide to RxJava by Hiroshi Kurokawa
Published July 21, 2016 in Technology

In this talk, I'm giving some advice about how to learn RxJava.

Reference
- RxJava - Wiki
https://github.com/ReactiveX/RxJava/wiki
- Introduction to Rx
http://www.introtorx.com/
- 101 Rx Samples
http://rxwiki.wikidot.com/101samples
- RxJS
http://reactivex.io/rxjs/
- JSFiddle
https://jsfiddle.net
- RxJS Sample - hydrakecat
https://jsfiddle.net/hydrakecat/f8tv1phn/
- RxJava Operators
http://reactivex.io/documentation/operators.html

Transcript

1. THE BEGINNER’S GUIDE TO RXJAVA 2016.09.16
 HIROSHI KUROKAWA (@HYDRAKECAT)
2. WHAT’S RXJAVA
3. WHAT’S RXJAVA ▸ Handle a sequence of data over time as a stream ▸ Instead of gathering them, responding to each of them
4. WHAT’S RXJAVA ▸ Handle a sequence of data over time as a stream ▸ Instead of gathering them, responding to each of them 1 2 3 4 5 6
5. WHAT’S RXJAVA ▸ Handle a sequence of data over time as a stream ▸ Instead of gathering them, responding to each of them 1 2 3 4 5 6 if ( % 2 == 0) x x square( )
6. WHAT’S RXJAVA ▸ Handle a sequence of data over time as a stream ▸ Instead of gathering them, responding to each of them 1 2 3 4 5 6 if ( % 2 == 0) x x square( ) 4 16 36
7. WHAT’S RXJAVA ▸ Handle a sequence of data over time as a stream ▸ Instead of gathering them, responding to each of them Observable.just(1, 2, 3, 4, 5, 6) .filter(x -> x % 2 == 0) .map(x -> x * x) .subscribe(System.out::println);
8. WHY DIFFICULT?
9. WHY DIFFICULT? 1. Many operators
10. WHY DIFFICULT? 1. Many operators all() amb() ambWith() and() asyncAction() asyncFunc() averageDouble() averageFloat() averageInteger() averageLong() buffer() cache() cast() chunkify() collect() combineLatest() concat() concatMap() concatWith()
11. WHY DIFFICULT? 1. Many operators all() amb() ambWith() and() asyncAction() asyncFunc() averageDouble() averageFloat() averageInteger() averageLong() buffer() cache() cast() chunkify() collect() combineLatest() concat() concatMap() concatWith() connect() contains() count() countLong() create() debounce() defaultIfEmpty() defer() deferFuture() deferCancellableFuture() delay() dematerialize() distinct() distinctUntilChanged() doOnCompleted() doOnEach() doOnError() doOnNext() doOnRequest()
12. WHY DIFFICULT? 1. Many operators all() amb() ambWith() and() asyncAction() asyncFunc() averageDouble() averageFloat() averageInteger() averageLong() buffer() cache() cast() chunkify() collect() combineLatest() concat() concatMap() concatWith() connect() contains() count() countLong() create() debounce() defaultIfEmpty() defer() deferFuture() deferCancellableFuture() delay() dematerialize() distinct() distinctUntilChanged() doOnCompleted() doOnEach() doOnError() doOnNext() doOnRequest() doOnSubscribe() doOnTerminate() doOnUnsubscribe() doWhile() elementAt() elementAtOrDefault() empty() error() exists() filter() finallyDo() first() firstOrDefault() flatMap() flatMapIterable() forEach() forIterable() from() fromAction()
13. WHY DIFFICULT? 1. Many operators all() amb() ambWith() and() asyncAction() asyncFunc() averageDouble() averageFloat() averageInteger() averageLong() buffer() cache() cast() chunkify() collect() combineLatest() concat() concatMap() concatWith() connect() contains() count() countLong() create() debounce() defaultIfEmpty() defer() deferFuture() deferCancellableFuture() delay() dematerialize() distinct() distinctUntilChanged() doOnCompleted() doOnEach() doOnError() doOnNext() doOnRequest() doOnSubscribe() doOnTerminate() doOnUnsubscribe() doWhile() elementAt() elementAtOrDefault() empty() error() exists() filter() finallyDo() first() firstOrDefault() flatMap() flatMapIterable() forEach() forIterable() from() fromAction() fromCallable() fromCancellableFuture() fromFunc0() fromFuture() fromRunnable() generate() generateAbsoluteTime() getIterator() groupBy() groupByUntil() groupJoin() ifThen() ignoreElements() interval() isEmpty() join() just() last() lastOrDefault()
14. WHY DIFFICULT? 1. Many operators 2. Some complicated concepts
15. WHY DIFFICULT? 1. Many operators 2. Some complicated concepts ‣ Hot/Cold observable
16. WHY DIFFICULT? 1. Many operators 2. Some complicated concepts ‣ Hot/Cold observable ‣ Scheduler
17. WHY DIFFICULT? 1. Many operators 2. Some complicated concepts ‣ Hot/Cold observable ‣ Scheduler ‣ Subscription
18. WHY DIFFICULT? 1. Many operators 2. Some complicated concepts ‣ Hot/Cold observable ‣ Scheduler ‣ Subscription ‣ Subject
19. WHY DIFFICULT? 1. Many operators 2. Some complicated concepts ‣ Hot/Cold observable ‣ Scheduler ‣ Subscription ‣ Subject ‣ Back pressure
20. GUIDE 1: READ THE DOCUMENT ReactiveX/RxJava Wiki https://github.com/ReactiveX/RxJava/wiki Introduction to Rx http://www.introtorx.com/ 101 Rx Samples http://rxwiki.wikidot.com/101samples
21. GUIDE 2: GET USED TO OPERATORS ▸ Play with Rx operators ▸ Understand how operators work with your heart
22. GUIDE 2: GET USED TO OPERATORS ▸ Play with Rx operators ▸ Understand how operators work with your heart ▸ RxJS ▸ http://reactivex.io/rxjs/ ▸ JSFiddle ▸ https://jsfiddle.net
23. SAMPLE ‣ https://jsfiddle.net/hydrakecat/f8tv1phn/
24. GUIDE 3: KNOW THE OPERATOR CATEGORIES ▸ Creating Observables ▸ Transforming Observables ▸ Filtering Observables ▸ Combining Observables ▸ Error Handling Observables ▸ Observable Utility Operators ▸ Conditional and Boolean Operators ▸ Mathematical and Aggregate Operators ▸ Connectable Observable Operators
25. CREATING OBSERVABLES ▸ just() ▸ empty() / never() / error() ▸ from() ▸ interval() / timer() ▸ range()
26. TRANSFORMING OBSERVABLES ▸ map() ▸ scan() ▸ concatMap() / flatMap() / switchMap() ▸ groupBy()
27. COMBINING OBSERVABLES ▸ zipWith() ▸ combineLatest() ▸ join() ▸ merge()
28. SOME HINTS ‣ Are you interested in more than one Observables?
 → Combining / Conditional
29. SOME HINTS ‣ Are you interested in more than one Observables?
 → Combining / Conditional ‣ Or just one Observable?
 → Transforming / Filtering
30. SOME HINTS ‣ Are you interested in more than one Observables?
 → Combining / Conditional ‣ Or just one Observable?
 → Transforming / Filtering ‣ Are you creating an Observable?
 → Creating
31. SOME HINTS ‣ Are you interested in more than one Observables?
 → Combining / Conditional ‣ Or just one Observable?
 → Transforming / Filtering ‣ Are you creating an Observable?
 → Creating A Decision Tree of Observable Operators (http://reactivex.io/documentation/operators.html)
32. EXAMPLE 1: NETWORK CALL
33. EXAMPLE 1: NETWORK CALL ‣ Wait until both the network calls return and then combine the responses
34. EXAMPLE 1: NETWORK CALL ‣ Wait until both the network calls return and then combine the responses ‣ Use zipWith()
35. EXAMPLE 1: NETWORK CALL ‣ Wait until both the network calls return and then combine the responses ‣ Use zipWith() service.getDataA() .zipWith(service.getDataB(), Pair::new) .subscribeOn(Schedulers.io()) .subscribe(subscriber);
36. EXAMPLE 1: NETWORK CALL ‣ Chain a sequence of network calls
37. EXAMPLE 1: NETWORK CALL ‣ Chain a sequence of network calls ‣ Use flatMap()
38. EXAMPLE 1: NETWORK CALL ‣ Chain a sequence of network calls ‣ Use flatMap() service.getDataA() .flatMap((a) -> service.getDataB().map((b) -> new Pair<>(a, b))) .subscribeOn(Schedulers.io()) .subscribe(subscriber);
39. EXAMPLE 2: HANDLE UI EVENTS
40. EXAMPLE 2: HANDLE UI EVENTS ‣ Enable a button only when all the input fields are valid
41. EXAMPLE 2: HANDLE UI EVENTS ‣ Enable a button only when all the input fields are valid ‣ Use combineLatest()
42. EXAMPLE 2: HANDLE UI EVENTS ‣ Enable a button only when all the input fields are valid ‣ Use combineLatest() Observable.combineLatest( inputValidators, booleans -> Arrays.stream(booleans).allMatch(b -> (Boolean) b) ).subscribe(subscriber);
43. EXAMPLE 2: HANDLE UI EVENTS ‣ Periodically do something while list view is idling
44. EXAMPLE 2: HANDLE UI EVENTS ‣ Periodically do something while list view is idling ‣ Use takeUntil()
45. EXAMPLE 2: HANDLE UI EVENTS ‣ Periodically do something while list view is idling ‣ Use takeUntil() ConnectableObservable<Boolean> idling = RxAbsListView.scrollEvents(list) .map(event -> event.scrollState() == SCROLL_STATE_IDLE) .distinctUntilChanged() .startWith(true) .publish(); idling.connect(); idling .filter(b -> b) .subscribe(aBool -> Observable.interval(1, TimeUnit.SECONDS) .takeUntil(idling.filter(b -> !b)) .subscribe(aLong -> appendLog(".")));
46. GUIDE 4: TAKE ADVANTAGE OF EXISTING RX LIBRARIES ‣ Don’t create your Observable with Observable.create()
47. GUIDE 4: TAKE ADVANTAGE OF EXISTING RX LIBRARIES ‣ Don’t create your Observable with Observable.create() ‣ Use libraries instead
48. GUIDE 4: TAKE ADVANTAGE OF EXISTING RX LIBRARIES ‣ Don’t create your Observable with Observable.create() ‣ Use libraries instead ‣ Network calls: Retrofit ‣ SQLite: SQLBrite ‣ UI events: RxBinding
49. GUIDE 4: TAKE ADVANTAGE OF EXISTING RX LIBRARIES ‣ Don’t create your Observable with Observable.create() ‣ Use libraries instead ‣ Network calls: Retrofit ‣ SQLite: SQLBrite ‣ UI events: RxBinding ‣ Or use Observable.from~() ‣ fromCallble() ‣ fromEmitter() ‣ etc.
50. GUIDE 5: HAVE FUN! (http://slides.com/robwormald/everything-is-a-stream#/)
51. TEXT SUMMARY ▸ Guide 1: Read the documents ▸ Guide 2: Get used to the operators ▸ Guide 3: Know the operator categories ▸ Guide 4: Take advantage of the existing libraries ▸ Guide 5: Have Fun