Reactive programming in android

Copyright ©2016 Talen5ca So8ware (I) Pvt Ltd. All rights reserved.
Reactive programming in android Kaushal Dhruw @drulabs

Copyright © 2016 Talen5ca So8ware (I) Pvt Ltd. All rights
reserved. Copyright ©2016 Talen5ca So8ware (I) Pvt Ltd. All rights reserved. 2 Agenda •  What is Reactive programming? And Why? •  Reactive extensions •  RxJava & RxAndroid •  Components of reactive programming •  Retrofit with RxJava •  Operators •  Testing

reserved. Copyright ©2016 Talen5ca So8ware (I) Pvt Ltd. All rights reserved. 3 Reactive programming •  Wikipedia –  It is an asynchronous programming paradigm concerned with data flows and propagation of change. •  In other words: –  Reactive programming is programming with asynchronous data streams.

reserved. Copyright ©2016 Talen5ca So8ware (I) Pvt Ltd. All rights reserved. 5 Why asynchronous? MyApp isn’t responding Jesus peeps you need to update this. worst game ever Did you even test this ? Is there a way to give -20 star? My dog can create a better app

reserved. Copyright ©2016 Talen5ca So8ware (I) Pvt Ltd. All rights reserved. 6 Reactive programming •  Wikipedia –  It is an asynchronous programming paradigm concerned with data flows and propagation of change. •  In other words: –  Reactive programming is programming with asynchronous data streams.

reserved. Copyright ©2016 Talen5ca So8ware (I) Pvt Ltd. All rights reserved. 12 Reactive programming Observer pattern Iterator pattern Functional support Create Combine Transform Chain Listen Filter Reduce Map

reserved. Copyright ©2016 Talen5ca So8ware (I) Pvt Ltd. All rights reserved. 13 Reactive Extensions (Rx) •  Reactive extensions (or Rx) is a library for composing asynchronous and event-based programs by using observable sequences

reserved. Copyright ©2016 Talen5ca So8ware (I) Pvt Ltd. All rights reserved. 14 Reactive Extensions (Rx) •  Reactive extensions (or Rx) is a library for composing and programs by using sequences simultaneous operations. perform some operation(s) when event is triggered or received. think of it as asynchronous immutable array.

reserved. Copyright ©2016 Talen5ca So8ware (I) Pvt Ltd. All rights reserved. 16 RxJava & RxAndroid •  RxJava is a Java VM implementation of ReactiveX. •  RxAndroid provides android specific bindings and extensions so RxJava can be used in android applications

18 Reactive Programming Components

reserved. Copyright ©2016 Talen5ca So8ware (I) Pvt Ltd. All rights reserved. 19 Components •  Source (emits data) – Emits data streams that can be passed between threads and consumed •  Subscriber (the observer or consumer) – Consumes data emitted from source •  Scheduler (threads and concurrency) –  Where to process and consume data

reserved. Copyright ©2016 Talen5ca So8ware (I) Pvt Ltd. All rights reserved. 20 Components Source (observable) Data => 1, 2, 3 From Network Database File Doesn’t ma9er Data received. Update UI Or local DB Subscriber (observer) Scheduler (concurrency) I/O thread UI thread ComputaGon thread subscribe dispose Time onNext(1) onNext(2) Error / complete onNext(3)

reserved. Copyright ©2016 Talen5ca So8ware (I) Pvt Ltd. All rights reserved. 21 Source Source (observable) Data => 1, 2, 3 From Network Database File Doesn’t ma9er Time onNext(1) onNext(2) Error / complete onNext(3)

reserved. Copyright ©2016 Talen5ca So8ware (I) Pvt Ltd. All rights reserved. 22 Source & Subscriber Source (observable) Data => 1, 2, 3 From Network Database File Doesn’t ma9er Time onNext(1) onNext(2) Error / complete onNext(3) Data received. Update UI Or local DB Subscriber (observer) subscribe dispose

reserved. Copyright ©2016 Talen5ca So8ware (I) Pvt Ltd. All rights reserved. 24 Schedulers Source (observable) Time Subscriber (observer) Scheduler (concurrency) I/O thread UI thread ComputaGon thread Abstract away concerns like: •  Low level threading •  SynchronizaGon •  Thread safety •  Concurrent data structure

reserved. Copyright ©2016 Talen5ca So8ware (I) Pvt Ltd. All rights reserved. 25 Schedulers Source (observable) Time Subscriber (observer) Scheduler (concurrency) I/O thread UI thread ComputaGon thread Decide where to execute what •  io() •  computa5on() •  newThread() •  from(Executer)

reserved. Copyright ©2016 Talen5ca So8ware (I) Pvt Ltd. All rights reserved. 26 Source, Subscriber & Scheduler Source (observable) Data => 1, 2, 3 From Network Database File Doesn’t ma9er Time onNext(1) onNext(2) Error / complete onNext(3) Data received. Update UI Or local DB Subscriber (observer) subscribe dispose Scheduler (concurrency) I/O thread UI thread ComputaGon thread

reserved. Copyright ©2016 Talen5ca So8ware (I) Pvt Ltd. All rights reserved. 27 Components Source (observable) Data => 1, 2, 3 From Network Database File Doesn’t ma9er Data received. Update UI Or local DB Subscriber (observer) Scheduler (concurrency) I/O thread UI thread ComputaGon thread subscribe dispose Time onNext(1) onNext(2) Error / complete onNext(3)

28 RxJava2 Core Types

reserved. Copyright ©2016 Talen5ca So8ware (I) Pvt Ltd. All rights reserved. 29 RxJava2 Core types o  Observer<T> o  XSource<T> §  XOnSubscribe<T> o  Disposable o  Consumer<T> o  XEmitter<T> o  Transformer<T, R> o  Schedulers o  Subject<T>

reserved. Copyright ©2016 Talen5ca So8ware (I) Pvt Ltd. All rights reserved. 30 RxJava2 Core types o  Observer<T> o  XSource<T> §  XOnSubscribe<T> o  Disposable o  Consumer<T> o  XEmitter<T> o  Transformer<T, R> o  Schedulers o  Subject<T> Methods: •  onSubscribe(Disposable) •  onNext(T) •  onError(Throwable) •  onCompleted()

reserved. Copyright ©2016 Talen5ca So8ware (I) Pvt Ltd. All rights reserved. 31 RxJava2 Core types o  Observer<T> o  XSource<T> §  XOnSubscribe<T> o  Disposable o  Consumer<T> o  XEmitter<T> o  Transformer<T, R> o  Schedulers o  Subject<T> Multi-valued base reactive abstract class Use factory methods to create observables OnSubscribe is a param in create method

reserved. Copyright ©2016 Talen5ca So8ware (I) Pvt Ltd. All rights reserved. 32 RxJava2 Core types o  Observer<T> o  XSource<T> §  XOnSubscribe<T> o  Disposable o  Consumer<T> o  XEmitter<T> o  Transformer<T, R> o  Schedulers o  Subject<T> Unsubscribe from the source. Methods: •  dispose() •  isDisposed()

reserved. Copyright ©2016 Talen5ca So8ware (I) Pvt Ltd. All rights reserved. 33 RxJava2 Core types o  Observer<T> o  XSource<T> §  XOnSubscribe<T> o  Disposable o  Consumer<T> o  XEmitter<T> o  Transformer<T, R> o  Schedulers o  Subject<T> Functional interface that accepts a single value Methods: •  accept(T) Used with various single value functions

reserved. Copyright ©2016 Talen5ca So8ware (I) Pvt Ltd. All rights reserved. 34 RxJava2 Core types o  Observer<T> o  XSource<T> §  XOnSubscribe<T> o  Disposable o  Consumer<T> o  XEmitter<T> o  Transformer<T, R> o  Schedulers o  Subject<T> Interface for emitting signals Methods: •  onNext(T) •  onError(Throwable) •  onComplete()

reserved. Copyright ©2016 Talen5ca So8ware (I) Pvt Ltd. All rights reserved. 35 RxJava2 Core types o  Observer<T> o  XSource<T> §  XOnSubscribe<T> o  Disposable o  Consumer<T> o  XEmitter<T> o  Transformer<T, R> o  Schedulers o  Subject<T> Interface for composing source. Transforms source by applying a function Methods: •  Observable<R> apply(Observable<T>)

reserved. Copyright ©2016 Talen5ca So8ware (I) Pvt Ltd. All rights reserved. 36 RxJava2 Core types o  Observer<T> o  XSource<T> §  XOnSubscribe<T> o  Disposable o  Consumer<T> o  XEmitter<T> o  Transformer<T, R> o  Schedulers o  Subject<T> Parameterizes concurrency Methods: •  io() •  computation() •  newThread() •  from(Executer)

reserved. Copyright ©2016 Talen5ca So8ware (I) Pvt Ltd. All rights reserved. 37 RxJava2 Core types o  Observer<T> o  XSource<T> §  XOnSubscribe<T> o  Disposable o  Consumer<T> o  XEmitter<T> o  Transformer<T, R> o  Schedulers o  Subject<T> Advanced reactive concept. Acts as both source and subscriber Use with caution

38 RxJava2 source

reserved. Copyright ©2016 Talen5ca So8ware (I) Pvt Ltd. All rights reserved. 39 Source •  Observable<T> •  Flowable<T> •  Single<T> •  Maybe<T> •  Completable<T> •  ObservableSource<T> •  Publisher<T> •  SingleSource<T> •  MaybeSource<T> •  CompletableSource<T>

reserved. Copyright ©2016 Talen5ca So8ware (I) Pvt Ltd. All rights reserved. 40 Observable •  Observable<T> •  Flowable<T> •  Single<T> •  Maybe<T> •  Completable<T> Emits 0 to N items terminates with success or exception

reserved. Copyright ©2016 Talen5ca So8ware (I) Pvt Ltd. All rights reserved. 41 Flowable •  Observable<T> •  Flowable<T> •  Single<T> •  Maybe<T> •  Completable<T> Emits 0 to N items terminates with success or exception. Supports backpressure

reserved. Copyright ©2016 Talen5ca So8ware (I) Pvt Ltd. All rights reserved. 42 Single •  Observable<T> •  Flowable<T> •  Single<T> •  Maybe<T> •  Completable<T> Emits single item or error. Has no completion indicator

reserved. Copyright ©2016 Talen5ca So8ware (I) Pvt Ltd. All rights reserved. 43 Maybe •  Observable<T> •  Flowable<T> •  Single<T> •  Maybe<T> •  Completable<T> Succeeds with 0 or 1 item, or fails. Has completion indicator. Reactive optional.

reserved. Copyright ©2016 Talen5ca So8ware (I) Pvt Ltd. All rights reserved. 44 Completable •  Observable<T> •  Flowable<T> •  Single<T> •  Maybe<T> •  Completable<T> Completes with success or fails. No emission.

reserved. Copyright ©2016 Talen5ca So8ware (I) Pvt Ltd. All rights reserved. 45 That was a lot to take in •  Source (Observable) and subscriber are just a slight extension of standard Observer Pattern ? •  The real power comes with reactive extensions •  operators that allows us to transform, combine, manipulate, and work with the sequences of emitted items One question:

46 Creating observables

reserved. Copyright ©2016 Talen5ca So8ware (I) Pvt Ltd. All rights reserved. 47 Creational operators •  Create •  Defer •  Empty/Never/Error •  From •  Interval •  Just •  Range •  Repeat •  Start •  Timer

reserved. Copyright ©2016 Talen5ca So8ware (I) Pvt Ltd. All rights reserved. 48 Creational operators •  Create •  Defer •  Empty/Never/Error •  From •  Interval •  Create an Observable from scratch by calling observer methods programmatically

reserved. Copyright ©2016 Talen5ca So8ware (I) Pvt Ltd. All rights reserved. 49 Creational operators •  Create •  Defer •  Empty/Never/Error •  From •  Interval •  Create fresh observable for each observer and defer creation until observer subscribes

reserved. Copyright ©2016 Talen5ca So8ware (I) Pvt Ltd. All rights reserved. 50 Creational operators •  Create •  Defer •  Empty/Never/Error •  From •  Interval •  Create observable that emits no items but terminates: –  Normally –  Never –  With error

reserved. Copyright ©2016 Talen5ca So8ware (I) Pvt Ltd. All rights reserved. 51 Creational operators •  Create •  Defer •  Empty/Never/Error •  From •  Interval •  Convert some other object or data structure into an Observable (like list, array, publisher etc.)

reserved. Copyright ©2016 Talen5ca So8ware (I) Pvt Ltd. All rights reserved. 52 Creational operators •  Create •  Defer •  Empty/Never/Error •  From •  Interval •  Create an Observable that emits a sequence of integers spaced by a particular time interval

reserved. Copyright ©2016 Talen5ca So8ware (I) Pvt Ltd. All rights reserved. 53 Creational operators •  Create •  Defer •  Empty/Never/Error •  From •  Interval •  Just •  Range •  Repeat •  Start •  Timer

reserved. Copyright ©2016 Talen5ca So8ware (I) Pvt Ltd. All rights reserved. 54 Creational operators •  Just •  Range •  Repeat •  Start •  Timer •  Convert an object or a set of objects into an Observable that emits that or those objects

reserved. Copyright ©2016 Talen5ca So8ware (I) Pvt Ltd. All rights reserved. 55 Creational operators •  Just •  Range •  Repeat •  Start •  Timer •  Create an Observable that emits a range of sequential integers

reserved. Copyright ©2016 Talen5ca So8ware (I) Pvt Ltd. All rights reserved. 56 Creational operators •  Just •  Range •  Repeat •  Start •  Timer •  Create an Observable that emits a particular item or sequence of items repeatedly

reserved. Copyright ©2016 Talen5ca So8ware (I) Pvt Ltd. All rights reserved. 57 Creational operators •  Just •  Range •  Repeat •  Start •  Timer •  Create an Observable that emits the return value of a function

reserved. Copyright ©2016 Talen5ca So8ware (I) Pvt Ltd. All rights reserved. 58 Creational operators •  Just •  Range •  Repeat •  Start •  Timer •  Create an Observable that emits a single item after a given delay

59 Transforming observables

67 Filtering operators

77 Combining observables

85 Retrofit and RxJava

reserved. Copyright ©2016 Talen5ca So8ware (I) Pvt Ltd. All rights reserved. 92 Thank you -Kaushal Dhruw @drulabs – twi]er / github / stackoverﬂow / medium Demo app available at h]ps://github.com/drulabs/PicBlast

reserved. Copyright ©2016 Talen5ca So8ware (I) Pvt Ltd. All rights reserved. 93 Next meetup suggestions •  RxKotlin with RxJava (android app development) •  RxSwift (iOS app development) •  Effective MVP using Dagger, Retrofit and RxJava •  Android architecture components

reserved. Copyright ©2016 Talen5ca So8ware (I) Pvt Ltd. All rights reserved. 94 References •  http://reactivex.io/documentation •  http://reactivemanifesto.org/ •  https://github.com/ReactiveX/RxJava/wiki •  https://medium.com/@andrestaltz/2-minute-introduction-to-rx-24c8ca793877 •  http://rxmarbles.com/ •  https://christinalee.github.io/Slides/slides-master/rx-android/ •  https://medium.com/@benlesh/hot-vs-cold-observables-f8094ed53339 •  https://github.com/Froussios/Intro-To-RxJava •  https://praveer09.github.io/ •  https://www.slideshare.net/allegrotech/rxjava-introduction-context •  https://gist.github.com/staltz/868e7e9bc2a7b8c1f754 •  http://www.vogella.com/tutorials/RxJava/article.html •  https://github.com/ReactiveX/RxJava •  BackPressure: https://github.com/ReactiveX/RxJava/wiki/Backpressure

Reactive programming in android

Reactive programming in android

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