2 презентация rx java+android

Reactive Programming
RxJava + Android

Rx Observer pattern
• Observable
• Observer/Subscriber
• Subscription
• Subject

onNext, onCompleted, and onError
new Observer<T>() {
@Override public void onNext(T element) {
// called when Observable «pushes» new event.
}
@Override public void onCompleted() {
// when stream is successfully completed(terminal state)
}
@Override public void onError(Throwable e) {
// bad news, stream is ends with exception (terminal state)
}
};

Rx Basics
http://reactivex.io/

- Emit 0 or N elements
- Fails with exception -> onError()
- Normally completes -> onCompleted()
Observable – Observer Contract

Stream creation
public static Observable<String> helloWorldStream() {
return Observable.create(new Observable.OnSubscribe<String>() {
@Override
public void call(Subscriber<? super String> subscriber) {
if (!subscriber.isUnsubscribed()) {
try {
subscriber.onNext("Hello");
subscriber.onNext("World");
subscriber.onCompleted();
} catch (Exception ex) {
subscriber.onError(ex);
}
}
}
});
}

Stream creation
public static Observable<String> helloWorldStream() {
return Observable.create(subscriber -> {
if (!subscriber.isUnsubscribed()) {
try {
subscriber.onNext("Hello");
subscriber.onNext("World");
subscriber.onCompleted();
} catch (Exception ex) {
subscriber.onError(ex);
}
}
});
}

Hello World
@Test public void helloWorldTest() {
Observable<String> stream = helloWorldStream();
stream.subscribe(result -> {
System.out.println(result);
}, err -> {
err.printStackTrace();
});
}

Hello World
stream.subscribe(result -> {
}, err -> {
});
}
"D:JVMJava JDKbinjava"
Hello
World
Process finished with exit code 0

Hello World
stream
.reduce((prev, newOne) -> prev + " " + newOne )
.subscribe(result -> {
}, err -> {
});
}
"D:JVMJava JDKbinjava"
Hello World
Process finished with exit code 0

Operators
Creating – create, defer, from, interval, timer, start . . .
Transforming – flatMap, map, scan, groupBy, buffer . . .
Filtering – filter, debounce, distinct, take , first, egnoreElements . . .
Combining – combineLatest, merge, startWith, switch, zip . . .
Conditional & Boolean – contains, skipWhile, takeWhile, takeUntil, all . . .
Math & Agregation – reduce, sum, min, max, count . . .
And others . . .
http://reactivex.io/documentation/operators.html

Creating operators
Observable.just(1, 2, 3, 4);
Observable.from(Arrays.asList(“zero", "one", "two", "three"));
Observable.interval(200, TimeUnit.MILLISECONDS);
Observable.error(new Exception(" :`( "));

Transforming operators
Observable.just(2, 4, 6, 8, 10, 25, 43)
.map(num -> new Pair<Integer, Double>(num, Math.sqrt(num)))
.subscribe(pair -> println("new element is -> " + pair));
Observable.just(2, 4, 6, 8, 10, 25, 43)
.scan((x, y ) -> x + y)
.subscribe(sum -> println("Sum is: (" + sum + ")"));

Filtering operators
Observable.just(2, 30, 22, 5, 60, 1)
.filter(num -> num > 10)
.subscribe(num -> println("Filtered -> " + num));

Combining operators
Observable<Integer> ones = Observable.just(1, 1, 1);
Observable<Integer> twos = Observable.just(2, 2);
Observable
.concat(ones, twos)
.subscribe(res -> System.out.println(res));

Combining operators
Observable<Integer> ones = Observable.just(1, 1, 1);
Observable<Integer> twos = Observable.just(2, 2);
Observable
.combineLatest(ones, twos, (o, t) -> "1 stream ->" + o + "n 2 stream -> " + t)
.subscribe(res -> System.out.println(res));

Conditional & Boolean operators
Observable<Integer> zeros = Observable.just(0, 0, 0).delay(200, MILLISECONDS);
Observable<Integer> nums = Observable.just(1, 2, 3).delay(100, MILLISECONDS);
Observable<Integer> dozens = Observable.just(10, 20, 60).delay(300, MILLISECONDS);
Observable.amb(zeros, nums, dozens)
.subscribe(res -> System.out.println(res)); // prints 1 2 3

RxBus
public class RxBus {
private RxBus() { throw new RuntimeException("Not allowed to create instance ");};
private static final Subject<Object, Object> bus =
new SerializedSubject<>(PublishSubject.create());
public static void send(Object o) {
bus.onNext(o);
}
public static Observable<Object> toObserverable() {
return bus.asObservable();
}
public static boolean hasObservers() {
return bus.hasObservers();
}
public static <T>Observable<T> observeEvent(Class<T> clazz) {
return bus.ofType(clazz).asObservable();
}
}

RxBus
public class MainActivity extends AppCompatActivity {
@Override protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
RxBus.send(new ActivityCreatedEvent());
// . . . more logic here
}
}

RxBus
public class MainActivity extends AppCompatActivity {
@Override protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
RxBus.send(new ActivityCreatedEvent());
// . . . more logic here
}
class SuperBusyService extends Service {
private final CompositeSubscription compSub = new CompositeSubscription();
@Override public void onCreate() {
super.onCreate();
compSub.add(RxBus.observEvent(ActivityCreatedEvent.class)
.subscribe(event -> doSomeLongOperation(), err -> handleErr(err)));
}
@Override public void onDestroy() {
super.onDestroy();
compSub.clear();
}
. . .

Simple Timer
public void launchTicker() {
final Long secondsDisabled = 60L; // user not allowed to send request for new sms
tickerSub = Observable.interval(1, TimeUnit.SECONDS)
.takeUntil(it -> it >= secondsDisabled -1 /* starts from 0 */ )
.map (sec -> (secondsDisabled - sec))
.observeOn(AndroidSchedulers.mainThread())
.doOnSubscribe (() -> llSendAgain.isEnabled = false )
.doOnCompleted (() -> llSendAgain.isEnabled = true)
.subscribe(time -> tvTicker.setText(getString(R.string.sms_send_again_timer, time))
, err -> handleError(err));
}

«Do» operators in action
public class HomeScreenPresenter {
final HomeView view;
final HomeInteractor interactor = new HomeInteractorImpl();
public HomeScreenPresenter(HomeView view){ this.view = view; }
public void getClientData(String token) {
view.showProgress();
view.manageSubscription(interactor.loadClientData(token)
.subscribeOn(Schedulers.io())
.subscribe(result -> {
view.hideProgress();
view.onDataReady(result);
}, err -> {
view.hideProgress();
view.handleError(err);
})
);
}
}

.doOnSubscribe(view::showProgress)
.doOnTerminate(view::hideProgress)
.subscribe(result -> { view.onDataReady(result); }, err -> { view.handleError(err);})
);
}
}

.compose(RxUtils.progressBarVisibility(view))
);
}
}

.compose(RxUtils.progressBarVisibility(view))
);
}
}
public static <T> Observable.Transformer<T, T> progressBarVisibility(HomeView view) {
return targetObservable ->
targetObservable.doOnSubscribe(view::showProgress)
.doOnTerminate(view::hideProgress);
}

Validation
final Observable<Boolean> nameObservable = RxTextView.textChanges(edtPassword)
.skip(1)
.map(text -> /* validateInput with side effect */);
final Observable<Boolean> emailObservable = RxTextView.textChanges(edtEmail)
.skip(1)
final Observable<Boolean> passwordObservable = RxTextView.textChanges(edtPassword)
.skip(1)
final Subscription combinedSub =
Observable
.combineLatest(nameObservable, emailObservable, passwordObservable,
(name, mail, pass) -> name && mail && pass)
.distinctUntilChanged()
.subscribe(btnProceed::setEnabled);
compositeSubscription.add(combinedSub);

«Live» search
RxTextView.textChanges(searchEditText)
.flatMap(ApiService::searchItems)
.subscribe(this::updateList, t-> showError());
https://lorentzos.com/improving-ux-with-rxjava-4440a13b157f#.19yawyfss

«Live» search
.debounce(205, TimeUnit.MILLISECONDS)
.flatMap(ApiService::searchItems)

«Live» search
.switchMap(ApiService::searchItems)

«Live» search
.onErrorResumeNext(err -> Observable.empty())

«Live» search
.retryWhen(new NetworkConnectivity())

«Live» search
.retryWhen(new NetworkConnectivityIncremental(context, 5, 15, SECONDS))

Easy concurrency
NetApiService.loadDocument(docId)
.observeOn(Schedulers.computation())
// want find matches or smth ASAP
.map(data -> MatchFinder.find(data, PATTERN))
// work done, can swith on low priority 'IO' pool
.observeOn(Schedulers.io())
.doOnNext(processedData -> DataProvider.saveProcessedDocument(docId, processedData))
.subscribe(/* do something with result */);

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2 презентация rx java+android

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