The Next Step for Reactive Android Programming

Reactive Android:The Next Steps

Futurice & upday

@tpolansk

Tomek Polanski

The Good

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Reactive Streamscompatibility

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4 interfaces 7 methods

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Flowable.just("- I'm RxJava!")

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Flowable.just("- I'm RxJava!")

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RxJava 2

Flux.from(Flowable.just("- I'm RxJava!"))

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RxJava 2

Flux.from(Flowable.just("- I'm RxJava!"))

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RxJava 2

Reactor 3

Flux.from(Flowable.just("- I'm RxJava!")) .map(msg -> msg + " - I'm Reactor!")

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RxJava 2

Flux.from(Flowable.just("- I'm RxJava!")) .map(msg -> msg + " - I'm Reactor!")

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Reactor 3

RxJava 2

Flux.from(Flowable.just("- I'm RxJava!")) .map(msg -> msg + " - I'm Reactor!") .subscribe(msg -> print(msg));

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RxJava 2

Flux.from(Flowable.just("- I'm RxJava!")) .map(msg -> msg + " - I'm Reactor!") .subscribe(msg -> print(msg));

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RxJava 2

Reactor 3

[2]

Backpressure

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Backpressure

Flowable&

Observable@tpolansk

Flowable:BUFFER, DROP,…

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Observable:Buffer-like

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Observable:Buffer-like

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Out Of Memory

Flowable?

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Flowable

Exception Is Really Likely

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Observable

Exception Is Not Likely

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Better Single and Completable

Integration @tpolansk

Observable.range(0, 10) .all(it -> it % 2 == 0)

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Observable.range(0, 10) .all(it -> it % 2 == 0)

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RxJava 1 - Observable

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RxJava 2 - Single

Observable.range(0, 10) .all(it -> it % 2 == 0)

Performance

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Performance

(-76%, +2800%)

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Memory

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Memory

50% less

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Testing

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Testing

.test()

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Observable.just(1)

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Observable.just(1) .test()

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Observable.just(1) .test() .assertValue(1)

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Observable.just(1) .test() .assertValue(1) .assertComplete();

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Observable.just(1) .test() .assertValue(1) .assertComplete();

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Soon in RxJava 1

[4]

Bye Bye nulls

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“1B$ Mistake” no more

[5]

The Bad

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Bye Bye nulls

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Removing takes time

Writing Operators

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10x HARDER*

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10x HARDER*

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Android Dev’s Nightmare

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AsyncTask?

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AsyncTask?

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Configuration Change?

AsyncTask?

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Styling? Configuration Change?

AsyncTask?

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Styling? Bluetooth LE?

Configuration Change?

AsyncTask?

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Styling? Java 7 Forever?Bluetooth LE?

Configuration Change?

Dex Limit

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RxJava 1.2.2

5600 @tpolansk

RxJava 2.0.1

9200 @tpolansk

5600 + 9200 = 14800

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5600 + 9200 = 14800

22% Dex Limit @tpolansk

The Migration

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upday’s RxJava integration

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Observable: 1224

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Observable: 1224

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Observable: 1224int: 1516

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Observable: 1224int: 1516

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Observable: 1224int: 1516

String: 3246@tpolansk

Observable: 1224int: 1516

String: 3246@tpolansk

Not in One Go!

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Update toThe Newest

RxJava 1.x.x@tpolansk[7]

Use

RxJava2Interop@tpolansk[8]

The Data Flow

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Network

UI

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Network

UI

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Network

UI

Start With Leafs

Not Roots

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// Activity

dataModel.getText() .subscribe(text -> view.setText(text));

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// Activity

dataModel.getText() .subscribe(text -> view.setText(text));

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RxJava 1

// Activity

RxJavaInterop .toV2Observable(dataModel.getText()) .subscribe(text -> view.setText(text));

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// Activity

RxJavaInterop .toV2Observable(dataModel.getText()) .subscribe(text -> view.setText(text));

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RxJava 1

// Activity

RxJavaInterop .toV2Observable(dataModel.getText()) .subscribe(text -> view.setText(text));

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RxJava 1

RxJava 2

// DataModel

Observable<String> getText() { return cache.getText();}

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// DataModel

Observable<String> getText() { return cache.getText();}

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RxJava 1

// DataModel

Observable<String> getText() { return RxJavaInterop .toV2Observable(cache.getText());}

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// DataModel

Observable<String> getText() { return RxJavaInterop .toV2Observable(cache.getText());}

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RxJava 2

// Activity

RxJavaInterop .toV2Observable(dataModel.getText()) .subscribe(text -> view.setText(text));

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RxJava 2

// Activity

dataModel.getText() .subscribe(text -> view.setText(text));

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RxJava 2

Replacing nulls

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Replacing nulls

Null Objects or

Optionals@tpolansk[9]

class User {String name;

User(String name) {this.name = name;

}}

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Observable<User> userStream = …

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Observable<User> userStream = ……userStream .filter(user -> user != null)

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class User {static final User EMPTY = new

User(“”);

String name;

public User(String name) {this.name = name;

}}

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Observable<User> userStream = ……userStream .filter(user -> !user.equals(User.EMPTY))

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The Frustrating

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NoSuchMethodError

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NoSuchMethodError

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Wait for libs update!

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First element?

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.first(…).firstOrError()

.singleElement()

.single(…)

.singleOrError()

.firstElement()

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.first(…).firstOrError()

.singleElement()

.single(…)

.singleOrError()

.firstElement()

?

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Relearn some operators

!

Migrating Tests

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TestSubscriber<Integer> ts = new TestSubscriber<>();

Observable.just(1).subscribe(ts);

ts.assertValue(1);

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TestSubscriber<Integer> ts = new TestSubscriber<>();

Observable.just(1).subscribe(ts);

ts.assertValue(1);

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TestObserver<Integer> to = new TestObserver<>();

Observable.just(1).subscribe(to);

to.assertValue(1);

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Observable.just(1) .test() .assertValue(1);

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Conclusion

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RxJava 2 Is Better!

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New Project?

Definitely RxJava 2

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Almost Done Project?

Should Not Migrate

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Anything Between?

It’s Always Up to You

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@tpolansk

[1] Reactive Streams – https://github.com/reactive-streams/reactive-streams-jvm[2] Reactor 3 - https://github.com/reactor/reactor-core[3] RxJava 2 Benchmark - https://github.com/akarnokd/akarnokd-misc/issues/2[4] test() operator in v1 - https://github.com/ReactiveX/RxJava/pull/4777[5] The Billion Dollar Mistake - https://www.infoq.com/presentations/Null-References-The-Billion-Dollar-Mistake-Tony-Hoare [6] Writing Operators - https://github.com/ReactiveX/RxJava/wiki/Writing-operators-for-2.0[7] RxJava releases - https://github.com/ReactiveX/RxJava/releases[8] RxJava2Interop - https://github.com/akarnokd/RxJava2Interop[9] Simple Options - https://github.com/tomaszpolanski/Options