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
   

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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?
   

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3. Nested Network Call w/o RxJava
   

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4. Nested Network Call w/ RxJava
   

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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
   

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6. Core RxJava Constructs
   ● Observable
   ● Observer
   ● Operator
   

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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
   

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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()
   

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9. Creating an Observable
   ● Create an Observable using #create(...)
   

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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(...)
    

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11. Creating an Observable (cont’d)
    ● Defer creation of Observable until subscription
    

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12. Subscribing to an Observable
    ● Observer has #onNext(...), #onCompleted(...), and #onError(...)
    

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13. Unsubscribing to an Observable
    ● Observable#subscribe(...) returns a Subscription object from which the
    caller can invoke Subscription#unsubscribe()
    

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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
    

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15. Operator
    

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16. Transforming an Observable
    ● Transform values emitted by Observable using the #map(...) operator
    

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17. Filtering an Observable
    ● Filter values emitted by Observable using #filter(...) operator
    

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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(...)
    

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19. Error Handling
    ● Re-subscribe/retry when the Observable emits an error
    

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20. Ex. Double Clicks
    ● Stream of clicks
    ● Accumulate clicks in a list
    ● Get length of list
    ● Filter
    

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21. Ex. Double Clicks
    Simulate a stream of clicks:
    

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22. Ex. Double Clicks
    Accumulate clicks until 250 ms has passed between clicks:
    

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23. Ex. Double Clicks
    Map the length of each list & filter for sizes >= 2:
    

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25. GitHub Example
    ● Interact with GitHub’s API using Retrofit and RxJava
    ○ https://github.com/arriolac/GithubRxJava
    

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26. Questions??
    

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27. Thank You!
    Twitter: @arriolachris
    

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