Introduction to RxJava on Android

Talk about RxJava basics and a coding exercise of using RxJava with Retrofit towards the end.

Transcript

1. Intro to RxJava on Android Chris Arriola Functional Reactive Programming
2. • Makes dealing with concurrency easy • Makes code a lot more concise and readable • Encourages defensive programming and makes error handling easy • Increases the level of abstraction Why consider RxJava?
3. Nested Network Call w/o RxJava
4. Nested Network Call w/ RxJava
5. What is RxJava? • Java implementation of .NET’s Reactive Extensions ◦ Specification for Functional Reactive Programming (FRP) • Programming with asynchronous data streams ◦ Not a new concept. Think: click events/handlers, event bus, etc. ◦ Reactive part • Can combine, create, filter, map, or transform any stream ◦ Functional part
6. Core RxJava Constructs • Observable • Observer • Operator
7. • Emits items in a sequence ◦ Like an Iterator, it produces all items in a sequence • Each emitted item will be propagated to each Observer Observable
8. Observer • Observer (aka the “subscriber”) subscribes to Observable • Observers are notified of a new item through #onNext(...) • Observers are notified when there sequence completes/fails through #onCompleted()/#onError()
9. Creating an Observable • Create an Observable using #create(...)
10. Creating an Observable • Create an Observable from item/s using #just(...) • Create an Observable from an Iterable using #from(...) • Create an Observable that emits items given an interval using #interval(...)
11. Creating an Observable (cont’d) • Defer creation of Observable until subscription
12. Subscribing to an Observable • Observer has #onNext(...), #onCompleted(...), and #onError(...)
13. Unsubscribing to an Observable • Observable#subscribe(...) returns a Subscription object from which the caller can invoke Subscription#unsubscribe()
14. Operator • Most powerful part about Observables is that you can transform them and perform functional style programming—map(), debounce(), filter(), etc. • Transform Observable instances through Operators
15. Operator
16. Transforming an Observable • Transform values emitted by Observable using the #map(...) operator
17. Filtering an Observable • Filter values emitted by Observable using #filter(...) operator
18. Scheduling an Observable • Specify a Scheduler where the Observable should operate using #subscribeOn(...), specify a Scheduler where the Observable should notify its observers using #observeOn(...)
19. Error Handling • Re-subscribe/retry when the Observable emits an error
20. Ex. Double Clicks • Stream of clicks • Accumulate clicks in a list • Get length of list • Filter
21. Ex. Double Clicks Simulate a stream of clicks:
22. Ex. Double Clicks Accumulate clicks until 250 ms has passed between clicks:
23. Ex. Double Clicks Map the length of each list & filter for sizes >= 2:
25. GitHub Example • Interact with GitHub’s API using Retrofit and RxJava ◦ https://github.com/arriolac/GithubRxJava
26. Questions??
27. Thank You! Twitter: @arriolachris