Presentation slide for Bekraf Developer Day Yogyakarta, 30 July 2016

1. RxJava in Action
Pratama Nur Wijaya
Android Developer - Kulina

2. RxJava is a Java VM implementation of ReactiveX
(Reactive Extensions): a library for composing
asynchronous and event-based programs by using
observable sequences.
RxJava ?

3. Why RxJava
Avoid callbackhell
Easy to compose and transform async process, combining,
filtering, etc
Error handling
It’s awesome

4. Cons RxJava
- Learning Curve

5. Implementation
dependencies {
compile 'io.reactivex:rxandroid:1.2.1'
compile 'io.reactivex:rxjava:1.1.6'
}

6. Observable
Observable<String> myObservable = Observable.create(
new Observable.OnSubscribe<String>() {
@Override public void call(Subscriber<? super String> subscriber)
{
try {
subscriber.onNext("Hello World");
subscriber.onCompleted();
} catch (Exception e) {
subscriber.onError(e);
}
}
});

7. Subscriber
Subscriber<String> mySubscriber = new Subscriber<String>() {
@Override public void onCompleted() {
Log.d(TAG, "onCompleted: Completed");
}
@Override public void onError(Throwable e) {
Log.e(TAG, "onError: Error " + e.getLocalizedMessage());
}
@Override public void onNext(String s) {
Log.d(TAG, "onNext: " + s);
}
};

8. Subscriber
myObservable.subscribe(mySubscriber);
// result : Hello World

9. Observable (Simplified)
Observable.just("Hello World")
.subscribe(new Subscriber<String>() {
@Override public void onCompleted() {
Log.d(TAG, "onCompleted: Completed");
}
@Override public void onError(Throwable e) {
Log.e(TAG, "onError: "+e.getLocalizedMessage() );
}
@Override public void onNext(String s) {
Log.d(TAG, "onNext: " + s);
}
});

10. More Simple ?
Use Retrolambda

11. Simplified With Lambda
buildscript {
repositories {
mavenCentral()
}
dependencies {
classpath 'me.tatarka:gradle-retrolambda:3.2.5'
}
}
// Required because retrolambda is on maven central
repositories {
mavenCentral()
}
apply plugin: 'com.android.application'
//or apply plugin: 'java'
apply plugin: 'me.tatarka.retrolambda'

12. Observable (Simplified with Retrolambda)
Observable.just("Hello World")
.subscribe(
s -> Log.d(TAG, "onNext: " + s),
throwable -> Log.e(TAG, "onError: " + throwable.getLocalizedMessage()),
() -> Log.d(TAG, "onCompleted: Completed"));

13. RxJava Operator

14. Observable.just(1, 2, 3, 4, 5)
.map(integer -> integer * 2)
.subscribe(result -> {
Log.d(TAG, "onCreate: result :"+result);
}, throwable -> {
Log.e(TAG, "onCreate: "+throwable.getLocalizedMessage());
}, () -> {
Log.i(TAG, "onCreate: finished");
});
// result : 2,4,6,8,10

15. Observable.just(1, 2, 3, 4, 5)
.filter(integer -> integer % 2 == 0)
.map(integer -> integer * 2)
.subscribe(result -> {
Log.d(TAG, "onCreate: result :" + result);
}, throwable -> {
Log.e(TAG, "onCreate: " + throwable.getLocalizedMessage());
}, () -> {
Log.i(TAG, "onCreate: finished");
});
// result : 4,8

16. Check http://rxmarbles.com/ for more operator

17. RxJava + Asynchronous

18. Async
Observable.just(doNetworkOrLongOperation())
.subscribeOn(Schedulers.io())
.observeOn(AndroidSchedulers.mainThread())
.subscribe(s -> {
Log.d(TAG, "onCreate: " + s);
}, throwable -> {
Log.e(TAG, "onCreate: " + throwable.getLocalizedMessage());
}, () -> {
Log.i(TAG, "onCreate: completed");
});

19. RxJava + OkHttp

20. private Observable<String> getSomeString(){
return Observable.create(new Observable.OnSubscribe<String>() {
@Override public void call(Subscriber<? super String> subscriber) {
try{
OkHttpClient client = new OkHttpClient();
Request request = new Request.Builder().url("SOME URL").build();
Response response = client.newCall(request).execute();
if (response != null) {
final String result = response.body().string();
subscriber.onNext(result);
subscriber.onCompleted();
}
}catch (Exception e){
subscriber.onError(e);
}
}
});
}

21. RxJava + OkHttp
getSomeString().subscribeOn(Schedulers.io())
.observeOn(AndroidSchedulers.mainThread())
.subscribe(s -> {
Log.d(TAG, "onCreate: " + s);
}, throwable -> {
Log.e(TAG, "onCreate: " + throwable.getLocalizedMessage());
}, () -> {
Log.i(TAG, "onCreate: completed");
});

22. RxJava + Retrofit 2

23. RxJava + Retrofit 2.x
// dependencies
compile "com.squareup.retrofit2:adapter-rxjava:$RETROFIT_VERSION"
// setup retrofit
Retrofit retrofit = new Retrofit.Builder().baseUrl(BuildConfig.SERVER_URL)
.addCallAdapterFactory(RxJavaCallAdapterFactory.create())
.client(okHttpClient)
.build();

24. Service
@GET("get_post/") Observable<SinglePostResponse> getPost(@Query("id") int id);
// handle it on your presenter
dataManager.getPost(id, isUpdate)
.subscribeOn(Schedulers.io())
.observeOn(AndroidSchedulers.mainThread())
.subscribe(post -> {
if (post != null) {
// do something
}
}, throwable -> {
Log.e(TAG, "getArticleDetail: "+throwable.getLocalizedMessage() );
}, () -> {
Log.i(TAG, "getArticleDetail: completed");
});

25. Be careful of Memory leak

26. private CompositeSubscription compositeSubscription = new CompositeSubscription();
compositeSubscription.add(getSomeString().subscribeOn(Schedulers.io())
.observeOn(AndroidSchedulers.mainThread())
.subscribe(s -> {
Log.d(TAG, "onCreate: " + s);
}, throwable -> {
Log.e(TAG, "onCreate: " + throwable.getLocalizedMessage());
}, () -> {
Log.i(TAG, "onCreate: completed");
}));
@Override protected void onDestroy() {
super.onDestroy();
compositeSubscription.unsubscribe();
}

27. RxBinding Demo
https://github.com/pratamawijaya/RxJavaInAction

28. References
http://blog.danlew.net/2014/09/15/grokking-rxjava-part-1/
https://github.com/kaushikgopal/RxJava-Android-Samples
https://www.ykode.com/2015/02/20/android-frp-rxjava-
retrolambda.html
https://gist.github.com/staltz/868e7e9bc2a7b8c1f754

29. Q & A

30. Thanks
pratama@kulina.id
tama@fanboy.id | set.mnemonix@gmail.com
https://pratamawijaya.com