Introduction to RxJava for Android Developers

This talk aims to introduce RxJava and the concepts of Reactive Programming to Android developers. We will focus on the Android world, its challenges and how to tackle them using “reactive” open source libraries like RxAndroid, RxLifecycle and RxBindings.

1. Introduction to RxJava for Android Developers Marcelo Benites
2. Reactive Programming
3. Reactive Programming
4. ReactiveX is a combination of the best ideas from the Observer pattern, the Iterator pattern, and functional programming
7. Easily create event streams or data streams. CREATE
8. Easily create event streams or data streams. CREATE Compose and transform streams with query-like operators. COMBINE
9. Compose and transform streams with query-like operators. COMBINE Subscribe to any observable stream to perform side effects. LISTEN Easily create event streams or data streams. CREATE
11. RxJava
12. public interface Dog {
 
 public String getName();
 
 public boolean isTrained();
 }
13. public interface Dog {
 
 public String getName();
 
 public boolean isTrained();
 } public interface DogHandler {
 
 Observable<Dog> trainDogs();
 }
14. DogHandler john = DogHandlerFactory.get(DogHandlerFactory.JOHN);
 
 Observable<Dog> trainedDogs = john.trainDogs();
15. Create
16. public class John implements DogHandler { 
 @Override public Observable<Dog> trainDogs() {
 
 }
 }
17. public class John implements DogHandler { 
 @Override public Observable<Dog> trainDogs() {
 return Observable.just(new DummyDog("Marley"));
 }
 }
19. public class John implements DogHandler {
 
 @Override public Observable<Dog> trainDogs() {
 return Observable.from(
 Arrays.asList(new DummyDog("Marley"), 
 new DummyDog("Rocky"), 
 new DummyDog("Daisy")));
 }
 }
21. public class John implements DogHandler {
 
 @Override public Observable<Dog> trainDogs() {
 return Observable.fromCallable(() -> { 
 return new DummyDog("Marley");
 });
 }
 }
23. public class John implements DogHandler {
 
 @Override public Observable<Dog> trainDogs() {
 return Observable.defer(() -> {
 return Observable.just(new DummyDog("Marley"));
 });
 }
 }
25. public class John implements DogHandler {
 
 @Override public Observable<Dog> trainDogs() {
 return Observable.create(new Observable.OnSubscribe<Dog>() {
 @Override public void call(Subscriber<? super Dog> subscriber) {
 subscriber.onNext(new DummyDog("Marley"));
 subscriber.onNext(new DummyDog("Rocky"));
 subscriber.onCompleted();
 }
 });
 }
 }
26. public class John implements DogHandler {
 
 @Override public Observable<Dog> trainDogs() {
 return Observable.create(new Observable.OnSubscribe<Dog>() {
 @Override public void call(Subscriber<? super Dog> subscriber) {
 subscriber.onNext(new DummyDog("Marley"));
 subscriber.onNext(new DummyDog("Rocky"));
 subscriber.onCompleted();
 }
 });
 }
 }
27. Combine
28. public class John implements DogHandler {
 
 @Override public Observable<Dog> trainDogs() {
 return Observable.from(
 Arrays.asList(new DummyDog("Marley"), 
 new DummyDog("Rocky"), 
 new DummyDog("Daisy")));
 }
 }
29. public class John implements DogHandler {
 
 @Override public Observable<Dog> trainDogs() {
 return Observable.from( Arrays.asList(new DummyDog("Marley"), 
 new DummyDog("Rocky"), 
 new DummyDog("Daisy")))
 .map(dummyDog -> trainDog(dummyDog));
 }
 
 private Dog trainDog(Dog dog) {
 return new TrainedDog(dog.getName());
 }
 }
31. public class John implements DogHandler {
 
 @Override public Observable<Dog> trainDogs() {
 return Observable.from( Arrays.asList(new DummyDog("Marley"), 
 new DummyDog("Rocky"), 
 new DummyDog("Daisy")))
 .map(dummyDog -> trainDog(dummyDog));
 }
 
 private Dog trainDog(Dog dog) {
 return new TrainedDog(dog.getName());
 }
 }
32. public class John implements DogHandler {
 
 @Override public Observable<Dog> trainDogs() {
 return Observable.from( Arrays.asList(new DummyDog("Marley"), 
 new DummyDog("Rocky"), 
 new DummyDog(“Daisy"))) .filter(dummyDog -> !dummyDog.getName().equals(“Rocky"))
 .map(dummyDog -> trainDog(dummyDog));
 }
 
 private Dog trainDog(Dog dog) {
 return new TrainedDog(dog.getName());
 }
 }
34. public class Mary implements DogHandler {
 
 @Override public Observable<Dog> trainDogs() {
 return Observable.just(new DummyDog("Rocky"))
 .map(dummyDog -> trainDog(dummyDog));
 }
 
 private Dog trainDog(Dog dog) {
 return new TrainedDog(dog.getName());
 }
 }
35. DogHandler john = DogHandlerFactory.get(DogHandlerFactory.JOHN);
 
 Observable<Dog> trainedDogs = john.trainDogs();
36. DogHandler john = DogHandlerFactory.get(DogHandlerFactory.JOHN);
 DogHandler mary = DogHandlerFactory.get(DogHandlerFactory.MARY);
 
 Observable<Dog> trainedDogs = Observable.merge(john.trainDogs(), mary.trainDogs());
38. DogHandler john = DogHandlerFactory.get(DogHandlerFactory.JOHN);
 DogHandler mary = DogHandlerFactory.get(DogHandlerFactory.MARY);
 
 Observable<Dog> trainedDogs = Observable.concat(john.trainDogs(), mary.trainDogs());
40. public interface DogRepository {
 
 Observable<Dog> storedDogs();
 
 }
41. public class John implements DogHandler {
 
 private final DogRepository dogRepository;
 
 public John(DogRepository dogRepository) {
 this.dogRepository = dogRepository;
 }
 
 @Override public Observable<Dog> trainDogs() {
 return dogRepository.storedDogs()
 .filter(storedDog -> (!storedDog.isTrained() 
 && !storedDog.getName().equals(“Rocky")))
 .map(dummyDog -> trainDog(dummyDog));
 }
 
 private Dog trainDog(Dog dummyDog) {
 return new TrainedDog(dummyDog.getName());
 }
 }
42. DogHandler john = DogHandlerFactory.get(DogHandlerFactory.JOHN);
 DogHandler mary = DogHandlerFactory.get(DogHandlerFactory.MARY);
 
 Observable<Dog> trainedDogs = Observable.concat(john.trainDogs(), mary.trainDogs());
45. DogHandler john = DogHandlerFactory.get(DogHandlerFactory.JOHN);
 DogHandler mary = DogHandlerFactory.get(DogHandlerFactory.MARY);
 
 Observable<Dog> trainedDogs = Observable.concat(john.trainDogs().take(3), mary.trainDogs());
47. RxBindings
48. Button button = (Button)findViewById(R.id.button); 
 Observable<Void> clicks = RxView.clicks(button)
49. Button button = (Button) findViewById(R.id.button);
 DogHandler john = DogHandlerFactory.get(DogHandlerFactory.JOHN);
 
 Observable<Dog> trainedDogs = RxView.clicks(button).flatMap(click -> john.trainDogs());
51. Button button = (Button) findViewById(R.id.button);
 DogHandler john = DogHandlerFactory.get(DogHandlerFactory.JOHN);
 
 Observable<Dog> trainedDogs = RxView.clicks(button).concatMap(click -> john.trainDogs());
53. Listen
54. trainedDogs.subscribe(new Observer<Dog>() {
 @Override public void onCompleted() {
 
 }
 
 @Override public void onError(Throwable e) {
 
 }
 
 @Override public void onNext(Dog dog) {
 
 }
 });
55. Subscription subscription = trainedDogs
 .subscribe(new Observer<Dog>() {
 @Override public void onCompleted() {
 
 }
 
 @Override public void onError(Throwable e) {
 
 }
 
 @Override public void onNext(Dog dog) {
 
 }
 });
57. subscription.unsubscribe();
58. RxLifecycle
59. public class MainActivity extends RxAppCompatActivity {
 …
 }
60. @Override protected void onResume() {
 super.onResume();
 trainedDogs
 .compose(bindToLifecycle())
 .subscribe(new Observer<Dog>() {
 
 @Override public void onCompleted() {
 
 }
 
 @Override public void onError(Throwable e) {
 
 }
 
 @Override public void onNext(Dog dog) {
 
 }
 });
 }
61. @Override protected void onResume() {
 super.onResume();
 trainedDogs
 .compose(bindUntilEvent(ActivityEvent.DESTROY))
 .subscribe(new Observer<Dog>() {
 
 @Override public void onCompleted() {
 
 }
 
 @Override public void onError(Throwable e) {
 
 }
 
 @Override public void onNext(Dog dog) {
 
 }
 });
 }
62. RxAppCompatActivity view = MainActivity.this;
 view.lifecycle()
 .filter(activityEvent -> activityEvent.equals(ActivityEvent.RESUME))
 .flatMap(resume -> john.trainDogs())
 .compose(view.bindUntilEvent(ActivityEvent.DESTROY))
 .subscribe(new Observer<Dog>() {
 @Override public void onCompleted() {
 
 }
 
 @Override public void onError(Throwable e) {
 
 }
 
 @Override public void onNext(Dog dog) {
 
 }
 });
63. RxAppCompatActivity view = MainActivity.this;
 view.lifecycle()
 .filter(activityEvent -> activityEvent.equals(ActivityEvent.RESUME))
 .flatMap(resume -> john.trainDogs())
 .compose(view.bindUntilEvent(ActivityEvent.DESTROY))
 .subscribe(new Observer<Dog>() {
 @Override public void onCompleted() {
 
 }
 
 @Override public void onError(Throwable e) {
 
 }
 
 @Override public void onNext(Dog dog) {
 
 }
 });
64. RxAppCompatActivity view = MainActivity.this;
 view.lifecycle()
 .filter(activityEvent -> activityEvent.equals(ActivityEvent.RESUME))
 .flatMap(resume -> john.trainDogs())
 .compose(view.bindUntilEvent(ActivityEvent.DESTROY))
 .subscribe(new Observer<Dog>() {
 @Override public void onCompleted() {
 
 }
 
 @Override public void onError(Throwable e) {
 
 }
 
 @Override public void onNext(Dog dog) {
 
 }
 });
65. RxAppCompatActivity view = MainActivity.this;
 view.lifecycle()
 .filter(activityEvent -> activityEvent.equals(ActivityEvent.RESUME))
 .flatMap(resume -> john.trainDogs())
 .compose(view.bindUntilEvent(ActivityEvent.DESTROY))
 .subscribe(new Observer<Dog>() {
 @Override public void onCompleted() {
 
 }
 
 @Override public void onError(Throwable e) {
 
 }
 
 @Override public void onNext(Dog dog) {
 
 }
 });
66. RxAppCompatActivity view = MainActivity.this;
 view.lifecycle()
 .filter(activityEvent -> activityEvent.equals(ActivityEvent.RESUME))
 .flatMap(resume -> john.trainDogs())
 .compose(view.bindUntilEvent(ActivityEvent.DESTROY))
 .subscribe(new Observer<Dog>() {
 @Override public void onCompleted() {
 
 }
 
 @Override public void onError(Throwable e) {
 
 }
 
 @Override public void onNext(Dog dog) {
 
 }
 });
68. RxAppCompatActivity view = MainActivity.this;
 view.lifecycle()
 .filter(activityEvent -> activityEvent.equals(ActivityEvent.RESUME))
 .flatMap(resume -> john.trainDogs())
 .compose(view.bindUntilEvent(ActivityEvent.DESTROY))
 .subscribe(new Observer<Dog>() {
 @Override public void onCompleted() {
 
 }
 
 @Override public void onError(Throwable e) {
 
 }
 
 @Override public void onNext(Dog dog) {
 
 }
 });
69. RxAppCompatActivity view = MainActivity.this;
 view.lifecycle()
 .filter(activityEvent -> activityEvent.equals(ActivityEvent.RESUME))
 .compose(view.bindUntilEvent(ActivityEvent.DESTROY)) .flatMap(resume -> john.trainDogs())
 .subscribe(new Observer<Dog>() {
 @Override public void onCompleted() {
 
 }
 
 @Override public void onError(Throwable e) {
 
 }
 
 @Override public void onNext(Dog dog) {
 
 }
 });
70. RxAppCompatActivity view = MainActivity.this;
 view.lifecycle()
 .filter(activityEvent -> activityEvent.equals(ActivityEvent.RESUME))
 .compose(view.bindUntilEvent(ActivityEvent.DESTROY)) .flatMap(resume -> john.trainDogs())
 .subscribe(new Observer<Dog>() {
 @Override public void onCompleted() {
 
 }
 
 @Override public void onError(Throwable e) {
 
 }
 
 @Override public void onNext(Dog dog) {
 
 }
 });
71. Threading
72. Schedulers.io();
 
 Schedulers.computation();
 
 Schedulers.newThread();
 
 Schedulers.immediate();
 
 Schedulers.from(Executors.newSingleThreadExecutor());
73. Schedulers.io();
 
 Schedulers.computation();
 
 Schedulers.newThread();
 
 Schedulers.immediate();
 
 Schedulers.from(Executors.newSingleThreadExecutor());
74. Schedulers.io();
 
 Schedulers.computation();
 
 Schedulers.newThread();
 
 Schedulers.immediate();
 
 Schedulers.from(Executors.newSingleThreadExecutor());
75. Schedulers.io();
 
 Schedulers.computation();
 
 Schedulers.newThread();
 
 Schedulers.immediate();
 
 Schedulers.from(Executors.newSingleThreadExecutor());
76. Schedulers.io();
 
 Schedulers.computation();
 
 Schedulers.newThread();
 
 Schedulers.immediate();
 
 Schedulers.from(Executors.newSingleThreadExecutor());
77. Schedulers.io();
 
 Schedulers.computation();
 
 Schedulers.newThread();
 
 Schedulers.immediate();
 
 Schedulers.from(Executors.newSingleThreadExecutor());
78. public interface DogWebService {
 
 Dog getDog();
 
 }
79. public class John implements DogHandler {
 
 private final DogWebService dogWebService;
 
 public John(DogWebService dogWebService) {
 this.dogWebService = dogWebService;
 }
 
 @Override public Observable<Dog> trainDogs() {
 return Observable.fromCallable(() -> {
 return dogWebService.getDog();
 })
 .map(dummyDog -> trainDog(dummyDog));
 }
 
 private Dog trainDog(Dog dummyDog) {
 return new TrainedDog(dummyDog.getName());
 }
 }
80. @Override public Observable<Dog> trainDogs() {
 return Observable.fromCallable(() -> {
 return dogWebService.getDog();
 })
 .map(dummyDog -> trainDog(dummyDog)) .subscribeOn(Schedulers.io());
 }
81. @Override public Observable<Dog> trainDogs() {
 return Observable.fromCallable(() -> {
 return dogWebService.getDog();
 })
 .map(dummyDog -> trainDog(dummyDog)) .subscribeOn(Schedulers.io());
 }
82. @Override public Observable<Dog> trainDogs() {
 return Observable.fromCallable(() -> {
 return dogWebService.getDog();
 })
 .map(dummyDog -> trainDog(dummyDog)) .subscribeOn(Schedulers.io()) .subscribeOn(Schedulers.computation());
 }
83. @Override public Observable<Dog> trainDogs() {
 return Observable.fromCallable(() -> {
 return dogWebService.getDog();
 })
 .map(dummyDog -> trainDog(dummyDog)) .subscribeOn(Schedulers.io()) .subscribeOn(Schedulers.computation());
 }
84. @Override public Observable<Dog> trainDogs() {
 return Observable.just(dogWebService.getDog()) .subscribeOn(Schedulers.io()) .map(dummyDog -> trainDog(dummyDog));
 }
 ?
85. @Override public Observable<Dog> trainDogs() {
 return Observable.just(dogWebService.getDog()) .subscribeOn(Schedulers.io()) .map(dummyDog -> trainDog(dummyDog));
 }

86. final TextView text = (TextView) findViewById(R.id.text);
 
 john.trainDogs()
 .subscribe(new Observer<Dog>() {
 @Override public void onCompleted() {
 
 }
 
 @Override public void onError(Throwable e) {
 
 }
 
 @Override public void onNext(Dog dog) {
 text.setText(dog.getName());
 }
 });
87. RxAndroid
88. final TextView text = (TextView) findViewById(R.id.text);
 
 john.trainDogs() .observeOn(AndroidSchedulers.mainThread())
 .subscribe(new Observer<Dog>() {
 @Override public void onCompleted() {
 
 }
 
 @Override public void onError(Throwable e) {
 
 }
 
 @Override public void onNext(Dog dog) {
 text.setText(dog.getName());
 }
 });
89. final TextView text = (TextView) findViewById(R.id.text);
 
 john.trainDogs() .observeOn(AndroidSchedulers.mainThread())
 .subscribe(new Observer<Dog>() {
 @Override public void onCompleted() {
 
 }
 
 @Override public void onError(Throwable e) {
 
 }
 
 @Override public void onNext(Dog dog) {
 text.setText(dog.getName());
 }
 });
90. final TextView text = (TextView) findViewById(R.id.text);
 
 john.trainDogs() .observeOn(AndroidSchedulers.mainThread()) .observeOn(Schedulers.io())
 .subscribe(new Observer<Dog>() {
 @Override public void onCompleted() {
 
 }
 
 @Override public void onError(Throwable e) {
 
 }
 
 @Override public void onNext(Dog dog) {
 text.setText(dog.getName());
 }
 });
91. final TextView text = (TextView) findViewById(R.id.text);
 
 john.trainDogs() .observeOn(AndroidSchedulers.mainThread()) .observeOn(Schedulers.io())
 .subscribe(new Observer<Dog>() {
 @Override public void onCompleted() {
 
 }
 
 @Override public void onError(Throwable e) {
 
 }
 
 @Override public void onNext(Dog dog) {
 text.setText(dog.getName());
 }
 });
92. final TextView text = (TextView) findViewById(R.id.text);
 
 john.trainDogs() .observeOn(AndroidSchedulers.mainThread()) .doOnNext(trainedDog -> text.setText(trainedDog.getName())) .observeOn(Schedulers.io())
 .subscribe(new Observer<Dog>() {
 @Override public void onCompleted() {
 
 }
 
 @Override public void onError(Throwable e) {
 
 }
 
 @Override public void onNext(Dog dog) {
 text.setText(dog.getName());
 }
 });
93. final TextView text = (TextView) findViewById(R.id.text);
 
 john.trainDogs() .observeOn(AndroidSchedulers.mainThread()) .doOnNext(trainedDog -> text.setText(trainedDog.getName())) .observeOn(Schedulers.io())
 .subscribe(new Observer<Dog>() {
 @Override public void onCompleted() {
 
 }
 
 @Override public void onError(Throwable e) {
 
 }
 
 @Override public void onNext(Dog dog) {
 text.setText(dog.getName());
 }
 });
94. final TextView text = (TextView) findViewById(R.id.text);
 
 john.trainDogs() .observeOn(AndroidSchedulers.mainThread()) .doOnNext(trainedDog -> text.setText(trainedDog.getName())) .delay(5, TimeUnit.SECONDS)
 .subscribe(new Observer<Dog>() {
 @Override public void onCompleted() {
 
 }
 
 @Override public void onError(Throwable e) {
 
 }
 
 @Override public void onNext(Dog dog) {
 text.setText(dog.getName());
 }
 });
95. final TextView text = (TextView) findViewById(R.id.text);
 
 john.trainDogs() .observeOn(AndroidSchedulers.mainThread()) .doOnNext(trainedDog -> text.setText(trainedDog.getName())) .delay(5, TimeUnit.SECONDS)
 .subscribe(new Observer<Dog>() {
 @Override public void onCompleted() {
 
 }
 
 @Override public void onError(Throwable e) {
 
 }
 
 @Override public void onNext(Dog dog) {
 text.setText(dog.getName());
 }
 });
96. Error Handling
97. john.trainDogs()
 .subscribe(new Observer<Dog>() {
 @Override public void onCompleted() {
 
 }
 
 @Override public void onError(Throwable e) {
 
 }
 
 @Override public void onNext(Dog dog) {
 
 }
 });
98. john.trainDogs()
 .subscribe(new Observer<Dog>() {
 @Override public void onCompleted() {
 
 }
 
 @Override public void onError(Throwable e) {
 
 }
 
 @Override public void onNext(Dog dog) {
 
 }
 });
99. john.trainDogs()
 .subscribe(new Observer<Dog>() {
 @Override public void onCompleted() {
 
 }
 
 @Override public void onError(Throwable e) {
 
 }
 
 @Override public void onNext(Dog dog) {
 
 }
 });
100. john.trainDogs()
 .subscribe(dog -> { /*Next dog*/});
101. OnErrorNotImplementedException
103. Thank You! Questions?