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Rx Java
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berglind
October 11, 2015
Technology
1
300
Rx Java
Intro to Rx Java and example how it's used in the QuizUp on Android
berglind
October 11, 2015
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Transcript
RxJava Siggi Jónsson - siggi@q.is
• RxJava is a Java VM implementation of Reactive Extensions:
a library for composing asynchronous and event-based programs by using observable sequences. What is RxJava?
• Java: RxJava • JavaScript: RxJS • C#: Rx.NET •
C#(Unity): UniRx • Scala: RxScala • Clojure: RxClojure • C++: RxCpp Platforms • Ruby: Rx.rb • Python: RxPY • Groovy: RxGroovy • JRuby: RxJRuby • Kotlin: RxKotlin • Swift: RxSwift • ObjC: ReactiveCocoa*
• Java: RxJava • JavaScript: RxJS • C#: Rx.NET •
C#(Unity): UniRx • Scala: RxScala • Clojure: RxClojure • C++: RxCpp Platforms • Ruby: Rx.rb • Python: RxPY • Groovy: RxGroovy • JRuby: RxJRuby • Kotlin: RxKotlin • Swift: RxSwift • ObjC: ReactiveCocoa*
• An awesome tool to work with asynchronous streams of
data What is RxJava?
• Button clicks • Text edits • Network requests •
Push notifications • …. What are streams?
What is not a stream?
The Past Life before RxJava
Asynchronous Operations • AsyncTasks • Callbacks • Handlers • Threads
• Runnables • Executors • EventBus
AsyncTask public class SomeTask extends AsyncTask<String, Void, SomeResult> { private
WeakReference<Callback> callback; public SomeTask(Callback callback) { callback = new WeakReference<Callback>(callback); } @Override protected SomeResult doInBackground(String... params) { try { //do stuff } catch (Exception e) { //oh god, what now? return null? } return null; } @Override protected void onPostExecute(SomeResult result) { if (callback.get() != null) { callback.onResult(result); } } }
Callback Hell button.setOnClickListener(new View.OnClickListener() { public void onClick(View v) {
loadPlayer(playerId, new Callback() { public void playerLoaded(Player p1) { loadPlayer(p1.bestFriendId, new Callback() { public void playerLoaded(Player p2) { loadImage(p2.profileUrl, new ImageCallback() { public void imageLoaded(Bitmap bitmap) { imageView.setImageBitmap(bitmap); } }); } }); } }); } });
• Did the player reach the Top 10 in a
topic in the first month after he joined or the first month after the topic was created (which ever is first)? Complexity grows fast
RxJava to the rescue
• Observable -> produces events • Observer/Subscriber -> receives events
• Operators • Schedulers -> Multithreading RxJava Concepts
Observable 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); } } });
Observable 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); } } });
Observable Observable.just("Hello, World!");
Observer interface Observer<T> { void onNext(T t); void onCompleted();
void onError(Throwable e); }
Putting it together Observable.just("Hello, World").subscribe(new Observer<String>() { @Override public void
onCompleted() { System.out.println("Done!"); } @Override public void onError(Throwable e) { System.err.println(e.getMessage()); } @Override public void onNext(String s) { System.out.println(s); } });
Putting it together Observable.just("Hello, World").subscribe(new Observer<String>() { @Override public void
onCompleted() { System.out.println("Done!"); } @Override public void onError(Throwable e) { System.err.println(e.getMessage()); } @Override public void onNext(String s) { System.out.println(s); } });
Putting it together Observable.just("Hello, World").subscribe(new Observer<String>() { @Override public void
onCompleted() { System.out.println("Done!"); } @Override public void onError(Throwable e) { System.err.println(e.getMessage()); } @Override public void onNext(String s) { System.out.println(s); } });
Putting it together Observable.just("Hello, World").subscribe(new Observer<String>() { @Override public void
onCompleted() { System.out.println("Done!"); } @Override public void onError(Throwable e) { System.err.println(e.getMessage()); } @Override public void onNext(String s) { System.out.println(s); } });
Putting it together Observable.just("Hello, World").subscribe(new Observer<String>() { @Override public void
onCompleted() { System.out.println("Done!"); } @Override public void onError(Throwable e) { System.err.println(e.getMessage()); } @Override public void onNext(String s) { System.out.println(s); } });
Putting it together Observable.just("Hello, World").subscribe(new Observer<String>() { @Override public void
onCompleted() { System.out.println("Done!"); } @Override public void onError(Throwable e) { System.err.println(e.getMessage()); } @Override public void onNext(String s) { System.out.println(s); } });
Putting it together api.getHello().subscribe(new Observer<String>() { @Override public void onCompleted()
{ System.out.println("Done!"); } @Override public void onError(Throwable e) { System.err.println(e.getMessage()); } @Override public void onNext(String s) { System.out.println(s); } });
Putting it together api.getHello().subscribe(new Observer<String>() { @Override public void onCompleted()
{ System.out.println("Done!"); } @Override public void onError(Throwable e) { System.err.println(e.getMessage()); } @Override public void onNext(String s) { System.out.println(s); } });
Operators The Toolbox
None
None
None
None
None
None
None
• Did the player reach the Top 10 in a
topic in the first month after he joined or the first month after the topic was created (which ever is first)? Complexity grows fast
Easy Observable.zip( playerService.getPlayer(“<player id>”), topicsService.getTopic("<topic id>”), player, topic -> {
if (player.created.before(topic.created)) return player.created; else return topic.created; } ).flatMap(date -> { return topicsService.getLeaderboard("<topic id>”, date); }).flatMap(leaderboard -> return Observable.from(leaderboard.top); }).exists(player -> { return player.id.equals("<player_id>"); });
Easy
Schedulers RxAndroid
Schedulers
Schedulers • Skipping Frames. The application may be doing too
much work on its main thread. • CalledFromWrongThreadException: Only the original thread that created a view hierarchy can touch its views. • NetworkOnMainThreadException • :(
Schedulers playerService.getFollowers() .subscribe(response -> { adapter.addAll(response.players); });
Schedulers playerService.getFollowers() .observeOn(AndroidSchedulers.mainThread()) .subscribe(response -> { adapter.addAll(response.players); });
Schedulers playerService.getFollowers() .observeOn(AndroidSchedulers.mainThread()) .subscribe(response -> { adapter.addAll(response.players); });
QuizUp Gameplay
QuizUp Round Observable<MatchEvent> events = Observable.concat( roundStarted(round), showQuestion(round, question).delay(ROUND_START_DELAY), showAnswers(round,
question).delay(showAnswersDelay), answerPeriodStart(round).delay(ANSWER_PERIOD_START_DELAY), Observable.merge( playerAnswer.takeUntil(timer), opponentAnswer.takeUntil(timer), timer.takeUntil(bothPlayersHaveAnswered) ), answerPeriodEnd(round), playerDidNotAnswer(round, question, playerDidAnswer), verifyOpponentIsStillHere(opponentDidAnswer), showCorrectAnswer(round, question).delay(SHOW_CORRECT_ANSWER_DELAY), Observable.empty().delaySubscription(FINISH_UP_ROUND_DELAY) );
QuizUp Round Observable<MatchEvent> events = Observable.concat( roundStarted(round), showQuestion(round, question).delay(ROUND_START_DELAY), showAnswers(round,
question).delay(showAnswersDelay), answerPeriodStart(round).delay(ANSWER_PERIOD_START_DELAY), Observable.merge( playerAnswer.takeUntil(timer), opponentAnswer.takeUntil(timer), timer.takeUntil(bothPlayersHaveAnswered) ), answerPeriodEnd(round), playerDidNotAnswer(round, question, playerDidAnswer), verifyOpponentIsStillHere(opponentDidAnswer), showCorrectAnswer(round, question).delay(SHOW_CORRECT_ANSWER_DELAY), Observable.empty().delaySubscription(FINISH_UP_ROUND_DELAY) );
QuizUp Round Observable<MatchEvent> events = Observable.concat( roundStarted(round), showQuestion(round, question).delay(ROUND_START_DELAY), showAnswers(round,
question).delay(showAnswersDelay), answerPeriodStart(round).delay(ANSWER_PERIOD_START_DELAY), Observable.merge( playerAnswer.takeUntil(timer), opponentAnswer.takeUntil(timer), timer.takeUntil(bothPlayersHaveAnswered) ), answerPeriodEnd(round), playerDidNotAnswer(round, question, playerDidAnswer), verifyOpponentIsStillHere(opponentDidAnswer), showCorrectAnswer(round, question).delay(SHOW_CORRECT_ANSWER_DELAY), Observable.empty().delaySubscription(FINISH_UP_ROUND_DELAY) );
QuizUp Round Observable<MatchEvent> events = Observable.concat( roundStarted(round), showQuestion(round, question).delay(ROUND_START_DELAY), showAnswers(round,
question).delay(showAnswersDelay), answerPeriodStart(round).delay(ANSWER_PERIOD_START_DELAY), Observable.merge( playerAnswer.takeUntil(timer), opponentAnswer.takeUntil(timer), timer.takeUntil(bothPlayersHaveAnswered) ), answerPeriodEnd(round), playerDidNotAnswer(round, question, playerDidAnswer), verifyOpponentIsStillHere(opponentDidAnswer), showCorrectAnswer(round, question).delay(SHOW_CORRECT_ANSWER_DELAY), Observable.empty().delaySubscription(FINISH_UP_ROUND_DELAY) );
QuizUp Round Observable<MatchEvent> events = Observable.concat( roundStarted(round), showQuestion(round, question).delay(ROUND_START_DELAY), showAnswers(round,
question).delay(showAnswersDelay), answerPeriodStart(round).delay(ANSWER_PERIOD_START_DELAY), Observable.merge( playerAnswer.takeUntil(timer), opponentAnswer.takeUntil(timer), timer.takeUntil(bothPlayersHaveAnswered) ), answerPeriodEnd(round), playerDidNotAnswer(round, question, playerDidAnswer), verifyOpponentIsStillHere(opponentDidAnswer), showCorrectAnswer(round, question).delay(SHOW_CORRECT_ANSWER_DELAY), Observable.empty().delaySubscription(FINISH_UP_ROUND_DELAY) );
QuizUp Round Observable<MatchEvent> events = Observable.concat( roundStarted(round), showQuestion(round, question).delay(ROUND_START_DELAY), showAnswers(round,
question).delay(showAnswersDelay), answerPeriodStart(round).delay(ANSWER_PERIOD_START_DELAY), Observable.merge( playerAnswer.takeUntil(timer), opponentAnswer.takeUntil(timer), timer.takeUntil(bothPlayersHaveAnswered) ), answerPeriodEnd(round), playerDidNotAnswer(round, question, playerDidAnswer), verifyOpponentIsStillHere(opponentDidAnswer), showCorrectAnswer(round, question).delay(SHOW_CORRECT_ANSWER_DELAY), Observable.empty().delaySubscription(FINISH_UP_ROUND_DELAY) );
QuizUp Round Observable<MatchEvent> events = Observable.concat( roundStarted(round), showQuestion(round, question).delay(ROUND_START_DELAY), showAnswers(round,
question).delay(showAnswersDelay), answerPeriodStart(round).delay(ANSWER_PERIOD_START_DELAY), Observable.merge( playerAnswer.takeUntil(timer), opponentAnswer.takeUntil(timer), timer.takeUntil(bothPlayersHaveAnswered) ), answerPeriodEnd(round), playerDidNotAnswer(round, question, playerDidAnswer), verifyOpponentIsStillHere(opponentDidAnswer), showCorrectAnswer(round, question).delay(SHOW_CORRECT_ANSWER_DELAY), Observable.empty().delaySubscription(FINISH_UP_ROUND_DELAY) );
QuizUp Round Observable<MatchEvent> events = Observable.concat( roundStarted(round), showQuestion(round, question).delay(ROUND_START_DELAY), showAnswers(round,
question).delay(showAnswersDelay), answerPeriodStart(round).delay(ANSWER_PERIOD_START_DELAY), Observable.merge( playerAnswer.takeUntil(timer), opponentAnswer.takeUntil(timer), timer.takeUntil(bothPlayersHaveAnswered) ), answerPeriodEnd(round), playerDidNotAnswer(round, question, playerDidAnswer), verifyOpponentIsStillHere(opponentDidAnswer), showCorrectAnswer(round, question).delay(SHOW_CORRECT_ANSWER_DELAY), Observable.empty().delaySubscription(FINISH_UP_ROUND_DELAY) );
QuizUp Round Observable<MatchEvent> events = Observable.concat( roundStarted(round), showQuestion(round, question).delay(ROUND_START_DELAY), showAnswers(round,
question).delay(showAnswersDelay), answerPeriodStart(round).delay(ANSWER_PERIOD_START_DELAY), Observable.merge( playerAnswer.takeUntil(timer), opponentAnswer.takeUntil(timer), timer.takeUntil(bothPlayersHaveAnswered) ), answerPeriodEnd(round), playerDidNotAnswer(round, question, playerDidAnswer), verifyOpponentIsStillHere(opponentDidAnswer), showCorrectAnswer(round, question).delay(SHOW_CORRECT_ANSWER_DELAY), Observable.empty().delaySubscription(FINISH_UP_ROUND_DELAY) );
QuizUp Round Observable<MatchEvent> events = Observable.concat( roundStarted(round), showQuestion(round, question).delay(ROUND_START_DELAY), showAnswers(round,
question).delay(showAnswersDelay), answerPeriodStart(round).delay(ANSWER_PERIOD_START_DELAY), Observable.merge( playerAnswer.takeUntil(timer), opponentAnswer.takeUntil(timer), timer.takeUntil(bothPlayersHaveAnswered) ), answerPeriodEnd(round), playerDidNotAnswer(round, question, playerDidAnswer), verifyOpponentIsStillHere(opponentDidAnswer), showCorrectAnswer(round, question).delay(SHOW_CORRECT_ANSWER_DELAY), Observable.empty().delaySubscription(FINISH_UP_ROUND_DELAY) );
QuizUp Round Observable<MatchEvent> events = Observable.concat( roundStarted(round), showQuestion(round, question).delay(ROUND_START_DELAY), showAnswers(round,
question).delay(showAnswersDelay), answerPeriodStart(round).delay(ANSWER_PERIOD_START_DELAY), Observable.merge( playerAnswer.takeUntil(timer), opponentAnswer.takeUntil(timer), timer.takeUntil(bothPlayersHaveAnswered) ), answerPeriodEnd(round), playerDidNotAnswer(round, question, playerDidAnswer), verifyOpponentIsStillHere(opponentDidAnswer), showCorrectAnswer(round, question).delay(SHOW_CORRECT_ANSWER_DELAY), Observable.empty().delaySubscription(FINISH_UP_ROUND_DELAY) );
QuizUp Round
QuizUp Round Observable<MatchEvent> events = Observable.concat( roundStarted(round), showQuestion(round, question).delay(ROUND_START_DELAY), showAnswers(round,
question).delay(showAnswersDelay), answerPeriodStart(round).delay(ANSWER_PERIOD_START_DELAY), Observable.merge( playerAnswer.takeUntil(timer), opponentAnswer.takeUntil(timer), timer.takeUntil(bothPlayersHaveAnswered) ), answerPeriodEnd(round), playerDidNotAnswer(round, question, playerDidAnswer), verifyOpponentIsStillHere(opponentDidAnswer), showCorrectAnswer(round, question).delay(SHOW_CORRECT_ANSWER_DELAY), Observable.empty().delaySubscription(FINISH_UP_ROUND_DELAY) );
All Rounds Observable<MatchEvent> match = Observable.range(1, 7).concatMap(round -> {
return round(round); });
All Rounds Observable<MatchEvent> match = Observable.range(1, 7).concatMap(round -> {
return round(round); });
All Rounds Observable<MatchEvent> match = Observable.range(1, 7).concatMap(round -> {
return round(round); });
All Rounds
Thank You q.is/jobs