This document discusses replacing the EventBus library with RxJava and RxAndroid for event handling in Android applications. It provides sample code for an RxEventBus class that can be used similarly to EventBus, posting and subscribing to events. It also discusses best practices like providing the RxEventBus as a singleton using Dagger 2 dependency injection.

1. Replace EventBus with
RxJava/RxAndroid
Hiroyuki Kusu ( @hkusu_ )
株式会社ゆめみ
2016/02/17 potatotips #26

2. Android 以外も色々やります。最近は主に JavaScript
( Node.js + ES2015 ) を書いてます。

3. greenrobot/EventBus
⇒ Replace with RxJava(RxAndroid)

4. app/build.gradle
dependencies {
// ...
compile 'io.reactivex:rxjava:1.1.0'
compile 'io.reactivex:rxandroid:1.1.0'
}

5. public class RxEventBus {
private final Subject<Object, Object> subject
= new SerializedSubject<>(PublishSubject.create());
public <T> Subscription onEvent(Class<T> clazz, Action1<T> handler) {
return subject
.ofType(clazz)
.subscribe(handler);
}
public void post(Object event) {
subject.onNext(event);
}
}
RxEventBus.java

6. public class RxEventBusProvider {
private static final RxEventBus rxEventBus = new RxEventBus();
public static RxEventBus provide(){
return rxEventBus;
}
}
RxEventBusProvider.java
※ providing the singleton instance

7. RxEventBus rxEventBus = RxEventBusProvider.provide();
rxEventBus.post(new ChangedEvent());
rxEventBus.onEvent(ChangedEvent.class, event -> {
// something..
});
※ applying Java8 & Retrolambda
Getting instance
Publish
Subscribe

8. Subscription subscription;
// ...
subscription = rxEventBus.onEvent(ChangedEvent.class, event -> {
// something..
});
// ...
subscription.unsubscribe();
Unsubscribe ( order not to leak)

9. Tips

10. public class RxEventBus {
private final Subject<Object, Object> subject
= new SerializedSubject<>(PublishSubject.create());
public <T> Subscription onEvent(Class<T> clazz, Action1<T> handler) {
return subject
.ofType(clazz)
.subscribe(handler);
}
public <T> Subscription onEventMainThread(Class<T> clazz, Action1<T> handler) {
return subject
.ofType(clazz)
.observeOn(AndroidSchedulers.mainThread())
.subscribe(handler);
}
public void post(Object event) {
subject.onNext(event);
}
}
Subscribing in the main thread

11. public class ChangedEvent {
private int id;
public ChangedEvent(int id) {
this.id = id;
}
public int getId() {
return id;
}
}
rxEventBus.post(new ChangedEvent(99));
rxEventBus.onEvent(ChangedEvent.class, event -> {
int id = event.getId();
// something..
});
Getting a value from the event

12. rxEventBus.onEvent(TodoRepository.ChangedEvent.class, event -> {
// something..
});
Create event as an inner class of the class to
publish (or subscribe) the event.
Because, it is unclear to post the event from
where(or to where).

13. Appendix
Providing a singleton instance
in Dagger2

14. @Module
public class AppModule {
@Provides
@Singleton
public RxEventBus provideRxEventBus(){
return new RxEventBus();
}
}
AppModule.java
@Component(modules = AppModule.class)
public interface AppComponent {
RxEventBus provideRxEventBus();
}
AppComponent.java

15. Getting instance
AppComponent appComponent = DaggerAppComponent.create();
// ...
RxEventBus rxEventBus = appComponent.provideRxEventBus();
In this example, Dagger2 looks redundant , but
redundant description can be reduced by
@inject annotation to the constructor.
See https://github.com/hkusu/android-dagger-rxjava-sample .

16. Sample code
hkusu/android-dagger-rxjava-sample

17. Thanks!