Practical RxJava for Android

Practical RxJava for Android

• 1.
  Practical RxJava forAndroid Tomáš Kypta @TomasKypta
• 2.
  What’s RxJava?
• 3.
  What’s RxJava? • composabledata flow • push concept • combination of • observer pattern • iterator pattern • functional programming
• 4.
  RxJava…not sure howAndroid apps…
• 5.
  Typical non-reactive app EventSource Views Network DB … Listener Listener Listener Listener logic logiclogiclogic State
• 6.
  Reactive app Transformation Event Source ObservableObservable Observable Observable … ObserverObserver Views Network DB
• 7.
  RxJava data flow Observable .from(newString[]{"Hello", "Droidcon!"}) creation
• 8.
  RxJava data flow Observable .from(newString[]{"Hello", "Droidcon!"}) .map(new Func1<String, String>() { @Override public String call(String s) { return s.toUpperCase(Locale.getDefault()); } }) creation
• 9.
  RxJava data flow Observable .from(newString[]{"Hello", "Droidcon!"}) .map(new Func1<String, String>() { @Override public String call(String s) { return s.toUpperCase(Locale.getDefault()); } }) .reduce(new Func2<String, String, String>() { @Override public String call(String s, String s2) { return s + ' ' + s2; } }) creation transformation
• 10.
  RxJava data flow Observable .from(newString[]{"Hello", "Droidcon!"}) .map(new Func1<String, String>() { @Override public String call(String s) { return s.toUpperCase(Locale.getDefault()); } }) .reduce(new Func2<String, String, String>() { @Override public String call(String s, String s2) { return s + ' ' + s2; } }) .subscribe(new Action1<String>() { @Override public void call(String s) { Timber.i(s); } }); creation transformation subscription
• 11.
  Java 8 &Android • use Retrolambda • or jack compiler • usable since build plugin 2.2.0
• 12.
  RxJava data flow Observable .from(newString[]{"Hello", "Droidcon!"}) .map(new Func1<String, String>() { @Override public String call(String s) { return s.toUpperCase(Locale.getDefault()); } }) .reduce(new Func2<String, String, String>() { @Override public String call(String s, String s2) { return s + ' ' + s2; } }) .subscribe(new Action1<String>() { @Override public void call(String s) { Timber.i(s); } }); creation transformation subscription
• 13.
  RxJava data flowwith Java 8 creation transformation subscription Observable .from(new String[]{"Hello", "Droidcon!"}) .map(s -> s.toUpperCase(Locale.getDefault())) .reduce((s,s2) -> s + ' ' + s2) .subscribe(s -> Timber.i(s));
• 14.
  Key parts • Observable •Observer or Subscriber • onNext(T) • onCompleted() • onError(Throwable) • Subject
• 15.
  What is RxJavagood for? • making code simple and readable • …with Java 8 • Async processing • no AsyncTask, AsyncTaskLoader, …
• 16.
  Why…??
• 17.
  Async composition • Asynccomposition • RxJava offers simple chaining of async operations • eliminates callback hell
• 18.
  RxJava 1 vs.RxJava 2
• 19.
  RxJava 1 vs.RxJava 2 • RxJava 2 in RC now • limited support in libraries • they will coexist for some time • different group ids • io.reactivex vs. io.reactivex.rxjava2 • different package names • rx vs. io.reactivex • https://github.com/ReactiveX/RxJava/wiki/What's-different-in-2.0
• 20.
  Operators
• 21.
  Operators • work onObservable • return an Observable • can be chained
• 22.
  Common mistakes • assumingmutability • operators return new Observable Observable<String> observable = Observable.from(new String[]{"Hello", "Droidcon!"}); obserable.map(s -> s.toUpperCase(Locale.getDefault())); obserable.reduce((s,s2) -> s + ' ' + s2);
• 23.
  Common Mistakes •assuming mutability •operatorsreturn new Observable Observable<String> observable = Observable.from(new String[]{"Hello", "Droidcon!"}) .map(s -> s.toUpperCase(Locale.getDefault())) .reduce((s,s2) -> s + ' ' + s2);
• 24.
  Marble diagrams • RxMarbles
• 25.
  Subscription
• 26.
  Subscription Subscription s =mAppInfoProvider.getAppsObservable() .subscribe( appInfo -> Timber.i(appInfo.getPackageName() );
• 27.
  Subscription Subscription s =mAppInfoProvider.getAppsObservable() .subscribe( appInfo -> Timber.i(appInfo.getPackageName() ); s.unsubscribe();
• 28.
  Subscription Subscription s =mAppInfoProvider.getAppsObservable() .subscribe( appInfo -> Timber.i(appInfo.getPackageName() ); s.unsubscribe(); Timber.i("unsubscribed: " + s.isUnsubscribed());
• 29.
  Subscription Subscription s =mAppInfoProvider.getAppsObservable() .subscribe( appInfo -> Timber.i(appInfo.getPackageName() ); s.unsubscribe(); Timber.i("unsubscribed: " + s.isUnsubscribed());
• 30.
  CompositeSubscription CompositeSubscription compositeSubscription = newCompositeSubscription();
• 31.
  CompositeSubscription CompositeSubscription compositeSubscription = newCompositeSubscription(); compositeSubscription.add(subscription);
• 32.
  CompositeSubscription CompositeSubscription compositeSubscription = newCompositeSubscription(); compositeSubscription.add(subscription); compositeSubscription.unsubscribe();
• 33.
  CompositeSubscription CompositeSubscription compositeSubscription = newCompositeSubscription(); compositeSubscription.add(subscription); compositeSubscription.unsubscribe(); compositeSubscription.clear();
• 34.
  CompositeSubscription CompositeSubscription compositeSubscription = newCompositeSubscription(); compositeSubscription.add(subscription); compositeSubscription.unsubscribe(); compositeSubscription.clear();
• 35.
  Bridging non-Rx APIs
• 36.
  Observable creation • create() •better to avoid private Object getData() {...} public Observable<Object> getObservable() { return Observable.create(subscriber -> { subscriber.onNext(getData()); subscriber.onCompleted(); }); }
• 37.
  Observable creation • just() privateObject getData() {...} public Observable<Object> getObservable() { return Observable.just(getData()); } !
• 38.
  just() & defer() •defer() private Object getData() {...} public Observable<Object> getObservable() { return Observable.defer( () -> Observable.just(getData()) ); }
• 39.
  Observable creation • fromCallable() •callable invoked when an observer subscribes private Object getData() {…} public Observable<Object> getObservable() { return Observable.fromCallable(new Callable<Object>() { @Override public String call() throws Exception { return getData(); } }); }
• 40.
  Observable creation fromasync APIs • fromEmitter() Observable.<Event>fromEmitter(emitter -> { Callback listener = new Callback() { @Override public void onSuccess(Event e) { emitter.onNext(e); if (e.isLast()) emitter.onCompleted(); } @Override public void onFailure(Exception e) { emitter.onError(e); } }; AutoCloseable c = api.someAsyncMethod(listener); emitter.setCancellation(c::close); }, BackpressureMode.BUFFER);
• 41.
  Subject
• 42.
  Subject • Observable &Observer • bridge between non-Rx API
• 43.
  Subject // consume anObservable.subscribe(aSubject); // produce aSubject.subscribe(aSubscriber);
• 44.
  Subject // bridging &multicasting aSubject.subscribe(subscriber1); aSubject.subscribe(subscriber2); aSubject.onNext(item1); aSubject.onNext(item2); aSubject.onNext(item2); aSubject.onCompleted()
• 45.
  Subject • stateful • terminalstate • don’t pass data after onComplete() or onError()
• 46.
  Subject • AsyncSubject • BehaviorSubject •ReplaySubject • PublishSubject • SerializedSubject
• 47.
  RxRelay
• 48.
  RxRelay • safer cousinof Subject • https://github.com/JakeWharton/RxRelay
• 49.
  RxRelay • Relay =Subject - onComplete() - onError() • Relay = Observable & Action1 • call() instead of onNext()
• 50.
  Subject vs. RxRelay •Subject • stateful • Relay • stateless
• 51.
  RxRelay Relay relay =… relay.subscribe(observer); relay.call(A); relay.call(B);
• 52.
  Threading
• 53.
  Threading • Parts ofa data flow can run on different threads! • Threading in RxJava defined by Schedulers
• 54.
  Schedulers • computation() • io() •newThread() • from(Executor)
• 55.
  Android Schedulers • mainThread() •from(Looper)
• 56.
  Threading • operators havetheir default Schedulers • check Javadoc!
• 57.
  Threading • just() • currentthread • delay(long, TimeUnit) • computation() thread
• 58.
  Threading • subscribeOn(Scheduler) • subscribesto Observable on the Scheduler • observeOn(Scheduler) • Observable emits on the Scheduler
• 59.
  subscribeOn() • multiple callsuseless • only the first call works! • for all operators
• 60.
  observeOn() • can becalled multiple times • changes Scheduler downstream
• 61.
  Side effect methods
• 62.
  Side effect methods •doOnNext() • doOnError() • doOnCompleted() • doOnSubscribe() • doOnUnsubscribe() • …
• 63.
  Async composition
• 64.
  Async composition apiEndpoint.login() .doOnNext(accessToken -> storeCredentials(accessToken))
• 65.
  Async composition apiEndpoint.login() .doOnNext(accessToken -> storeCredentials(accessToken)) .flatMap(accessToken-> serviceEndpoint.getUser())
• 66.
  Async composition apiEndpoint.login() .doOnNext(accessToken -> storeCredentials(accessToken)) .flatMap(accessToken-> serviceEndpoint.getUser()) .flatMap(user -> serviceEndpoint.getUserContact(user.getId()))
• 67.
  Async composition apiEndpoint.login() .doOnNext(accessToken -> storeCredentials(accessToken)) .flatMap(accessToken-> serviceEndpoint.getUser()) .flatMap(user -> serviceEndpoint.getUserContact(user.getId()))
• 68.
  Async composition
• 69.
  Android & RxJava
• 70.
  Android Lifecycle • fewcomplications • continuing subscription during configuration change • memory leaks
• 71.
  Android Lifecycle • continuingsubscription during configuration change • replay() • don’t use cache()
• 72.
  Android Lifecycle • memoryleaks • bind to Activity/Fragment lifecycle • use RxLifecycle
• 73.
  RxLifecycle
• 74.
  RxLifecycle • auto unsubscribebased on Activity/Fragment lifecycle myObservable .compose( RxLifecycle.bindUntilEvent( lifecycleObservable, ActivityEvent.DESTROY ) ) .subscribe(…); myObservable .compose(RxLifecycle.bindActivity(lifecycleObs)) .subscribe(…);
• 75.
  RxLifecycle • How toobtain ActivityEvent or FragmentEvent? A. rxlifecycle-components + subclass RxActivity, RxFragment B. Navi + rxlifecycle-navi C. Write it yourself
• 76.
  RxLifecycle public class MyActivityextends RxActivity { @Override public void onResume() { super.onResume(); myObservable .compose(bindToLifecycle()) .subscribe(); } }
• 77.
  RxLifecycle & Navi
• 78.
  Navi • https://github.com/trello/navi • betterlisteners for Activity/Fragment events • decoupling code from Activity/Fragment naviComponent.addListener(Event.CREATE, new Listener<Bundle>() { @Override public void call(Bundle bundle) { setContentView(R.layout.main); } } );
• 79.
  • converting lifecyclecallbacks into Observables! RxNavi RxNavi .observe(naviComponent, Event.CREATE) .subscribe(bundle -> setContentView(R.layout.main));
• 80.
  RxLifecycle & Navi publicclass MyActivity extends NaviActivity { private final ActivityLifecycleProvider provider = NaviLifecycle.createActivityLifecycleProvider(this); }
• 81.
  RxLifecycle & Navi publicclass MyActivity extends NaviActivity { private final ActivityLifecycleProvider provider = NaviLifecycle.createActivityLifecycleProvider(this); @Override public void onResume() { super.onResume(); myObservable .compose(provider.bindToLifecycle()) .subscribe(…); } }
• 82.
  RxLifecycle & customsolution public class MainActivityFragment extends Fragment { BehaviorSubject<FragmentEvent> mLifecycleSubject = BehaviorSubject.create(); }
• 83.
  RxLifecycle & customsolution public class MainActivityFragment extends Fragment { BehaviorSubject<FragmentEvent> mLifecycleSubject = BehaviorSubject.create(); @Override public void onPause() { super.onPause(); Timber.i("onPause"); mLifecycleSubject.onNext(FragmentEvent.PAUSE); } }
• 84.
  public class MainActivityFragmentextends Fragment { BehaviorSubject<FragmentEvent> mLifecycleSubject = BehaviorSubject.create(); @Override public void onPause() { super.onPause(); Timber.i("onPause"); mLifecycleSubject.onNext(FragmentEvent.PAUSE); } @Override public void onResume() { super.onResume(); myObservable // e.g. UI events Observable .compose( RxLifecycle .bindUntilEvent(mLifecycleSubject, FragmentEvent.PAUSE)) .doOnUnsubscribe(() -> Timber.i("onUnsubscribe")) .subscribe(…); } } RxLifecycle & custom solution
• 85.
  RxBinding
• 86.
  RxBinding RxView.clicks(vBtnSearch) .subscribe( v -> { Intentintent = new Intent(getActivity(), SearchActivity.class); startActivity(intent); } );
• 87.
  RxBinding RxTextView.textChanges(vEtSearch) .observeOn(Schedulers.io()) .flatMap(s -> mApiService.search(s.toString())) .subscribe( response-> Timber.i("Count: " + response.totalCount()) );
• 88.
  RxBinding RxTextView.textChanges(vEtSearch) .debounce(2, TimeUnit.SECONDS) .observeOn(Schedulers.io()) .flatMap(s ->mApiService.search(s.toString())) .subscribe( response -> Timber.i("Count: " + response.totalCount()) );
• 89.
  RxBinding RxTextView.textChanges(vEtSearch) .debounce(2, TimeUnit.SECONDS) .observeOn(Schedulers.io()) .flatMap(s ->mApiService.search(s.toString())) .flatMap(response -> Observable.from(response.getItems()) .subscribe( s -> Timber.i("item: " + s) );
• 90.
  Retrofit
• 91.
  Retrofit • sync orasync API (Retrofit 2) @GET("group/{id}/users") Call<List<User>> groupList(@Path("id") int groupId); @GET("group/{id}/users") Observable<List<User>> groupList(@Path("id") int groupId); • reactive API
• 92.
  Retrofit • onNext() withResponse, then onComplete() • onError() in case of error @GET("/data") Observable<Response> getData( @Body DataRequest dataRequest);
• 93.
  Retrofit RxTextView.textChanges(vEtSearch) .debounce(2, TimeUnit.SECONDS) .observeOn(Schedulers.io()) .flatMap(s -> mApiService.search(s.toString()) ) .flatMap(list-> Observable.from(list)) .subscribe( s -> Timber.i("item: " + s) );
• 94.
  Retrofit RxTextView.textChanges(vEtSearch) .debounce(2, TimeUnit.SECONDS) .observeOn(Schedulers.io()) .flatMap(s -> mApiService.search(s.toString()) ) .flatMap(list-> Observable.from(list)) .subscribe( s -> Timber.i("item: " + s) );
• 95.
  RxJava & SQLite •use SQLBrite • wrapper around SQLiteOpenHelper and ContentResolver SqlBrite sqlBrite = SqlBrite.create(); BriteDatabase db = sqlBrite .wrapDatabaseHelper(openHelper, Schedulers.io()); Observable<Query> users = db .createQuery("users", "SELECT * FROM users");
• 96.
  References • https://github.com/ReactiveX/RxJava • https://github.com/ReactiveX/RxAndroid •https://github.com/JakeWharton/RxRelay • https://github.com/trello/RxLifecycle • https://github.com/trello/navi • https://github.com/JakeWharton/RxBinding • https://github.com/square/retrofit • https://github.com/square/sqlbrite • advanced RxJava blog https://akarnokd.blogspot.com • http://slides.com/yaroslavheriatovych/frponandroid
• 97.
  Q&A