Apresentação sobre Reactive Programming no Android - RxAndroid dia 10/03/2016 no Android Meetup, Florianópolis - SC.

1. Reactive Programming on
Android

2. Erik Meijer - Rx .NET Ben Christensen - Rx Java
Introduction

3. Getting Started
Pull X Push

4. Getting Started
RxAndroid Dependency
compile 'io.reactivex:rxandroid:0.24.0'
Brings all you need
RXJava and RXAndroid

5. Anatomy
Observable.from(doLongNetworkOp())
.subcribeOn(Schedulers.io())
.observeOn(AndroidSchedulers.mainThread())
.subscribe(getObserver())
1. Observable
2. Observer
3. Schedulers

6. Anatomy
2. Observer.subscribe(getObserver())
private Observer<String> getObserver(){
new Observer<String>() {
@Override
public void onCompleted() { … }
@Override
public void onError(Throwable e) { … }
@Override
public void onNext(String string) { … }
};
}

7. Anatomy
Observable.from(doLongNetworkOp())
.subcribeOn(schedulers.io())
.observeOn(AndroidSchedulers.mainThread())
.subscribe(getObserver())
1. Observable
2. Observer
3. Schedulers
Observable Observer
4. Subscription
=

8. Subscription subscription = Observable.from(doLongNetworkOp())
.subcribeOn(Schedulers.io())
.observeOn(AndroidSchedulers.mainThread())
.subscribe(getObserver())
1. subscription.unsubscribe()
2. CompositeSubscription compSubscription;
compSubscription.add(subscription);
3. compSubscription.unsubscribe()
Anatomy

9. Getting Started - Producer and Consumer
Observable Observer
Emits
item1
item2
item3
Uses item 1
Uses item 2
Uses item 3
onNext(item1)
onNext(item2)
onNext(item3)
no more items onCompleted() complete
Ops! Error… onError(error) Handles error

10. AsyncTask → Observable/Observer
new FindUserTask().execute(userId);
private class FindUserTask extends AsyncTask<Long, Void, Void>{
@Override
protected void onPreExecute() {
showLoading();
}
@Override
protected User doInBackground(Long... params){
return userService.findUserById(params[0]);
}
@Override
protected void onPostExecute(User user){
mUserName.setText(user.getName());
hideLoading();
}
}
Observable
.just(userId)
.flatMap(new Func1<Long, Observable<User>>(){
@Override
public Observable<User> call(Long userId){
return Observable.just(userService.findUserById(userId);
})
.subscribeOn(Schedulers.io())
.subscribe(
new Observer<User>() {
@Override
public void onCompleted() {
Log.d(TAG, "onCompleted");
hideLoading();
}
@Override
public void onError(Throwable e) {
Log.d(TAG, "onError " + e.getMessage());
}
@Override
public void onNext(User user) {
Log.d(TAG, "onNext");
mUserName.setText(user.getName());
}
});

11. android.view.ViewRootImpl$CalledFromWrongThreadException: Only the original thread that created a
view hierarchy can touch its views.
Ops! Something went wrong

12. AsyncTask → Observable/Observer
Observable.just(userId)
.flatMap(new Func1<Long, Observable<User>>(){
@Override
public Observable<User> call(Long userId){
return Observable.just(service.findUserById(userId);
}
})
.subscribe(
new Observer<User>() {
@Override
public void onCompleted() { … }
@Override
public void onError(Throwable e) { … }
@Override
public void onNext(User user) { … }
});
.subscribeOn(Schedulers.io())
.observeOn(AndroidSchedulers.mainThread())

13. Operators
● Create
● From
● Just
● Filter
● Map
● Concat
● Many others...

14. Observable.create(new Observable.OnSubscribe<Integer>() {
@Override
public void call(Subscriber<? super Integer> observer) {
try {
if (!observer.isUnsubscribed()) {
for (int i = 1; i < 5; i++) {
observer.onNext(i);
}
observer.onCompleted();
}
} catch (Exception e) {
observer.onError(e);
}
}
} );
Operators - Create

15. Integer[] items = { 0, 1, 2, 3, 4, 5 };
Observable myObservable = Observable.from(items);
Operators - From

16. Observable.just(1, 2, 3)
.subscribe(new Subscriber<Integer>() {
@Override
public void onNext(Integer item) {
System.out.println(“onNext:” + item);
}
@Override
public void onError(Throwable error) {
System.err.println(“Error: ” + error.getMessage());
}
@Override
public void omCompleted() {
System.out.println("Sequence complete. ”);
}
});
Operators - Just

17. Observable.just(1, 2, 3, 4)
.filter(new Func1<Integer, Boolean>(){
@Override
public Boolean call(Integer number){
return (number < 4);
}
})
.subscribe(
new Subscriber<Integer>() {
@Override
public void onCompleted() { Log.d(TAG, "Sequence complete"); }
@Override
public void onError(Throwable e) { Log.d(TAG, "onError"); }
@Override
public void onNext(Integer number) { Log.d(TAG, "onNext " + number); }
});
onNext 1
onNext 2
onNext 3
Sequence complete
Operators - Filter

18. Operators - Map

19. Operators - Concat

20. http://reactivex.io/documentation/operators.html
http://rxmarbles.com
A Decision Tree of Observable Operators
I want to emit only certain items from an Observable
by filtering out those that do not match some predicate Filter
that is, only the first item First
that is, only the first items Take
that is, only the last item Last
Operators - Many Others

21. Questions ?