RxJava: combine two optional observables - java

I have two Observables, let's call them PeanutButter and Jelly. I'd like to combine them to a Sandwich Observable. I can do that using:
Observable<PeanutButter> peanutButterObservable = ...;
Observable<Jelly> jellyObservable = ...;
Observable<Sandwich> sandwichObservable = Observable.combineLatest(
peanutButterObservable,
jellyObservable,
(pb, j) -> makeSandwich(pb, j))
The problem is that RX waits for the first PeanutButter and the first Jelly to be emitted before emitting the first combined Sandwich but Jelly may never be emitted which means I never get the first Sandwich.
I'd like to combine the two feeds such that a combined item is emitted as soon as the first item from either feed is emitted, regardless of whether the other feed has yet to emit anything, how do I do that in RxJava?

one possible approach would be to use the startWith operator to trigger an emission of a known value from each stream upon subscription. this way combineLatest() will trigger if either stream emits a value. you'd just have to be mindful of looking out for the initial/signal values in the onNext consumer.
something like this...:
#Test
public void sandwiches() {
final Observable<String> peanutButters = Observable.just("chunky", "smooth")
.startWith("--initial--");
final Observable<String> jellies = Observable.just("strawberry", "blackberry", "raspberry")
.startWith("--initial--");
Observable.combineLatest(peanutButters, jellies, (peanutButter, jelly) -> {
return new Pair<>(peanutButter, jelly);
})
.subscribe(
next -> {
final String peanutButter = next.getFirst();
final String jelly = next.getSecond();
if(peanutButter.equals("--initial--") && jelly.equals("--initial--")) {
// initial emissions
} else if(peanutButter.equals("--initial--")) {
// jelly emission
} else if(jelly.equals("--initial--")) {
// peanut butter emission
} else {
// peanut butter + jelly emissions
}
},
error -> {
System.err.println("## onError(" + error.getMessage() + ")");
},
() -> {
System.out.println("## onComplete()");
}
);
}

I think this problem can be approached by using merge and scan operators:
public class RxJavaUnitTestJava {
public Observable<Sandwich> getSandwich(Observable<Jelly> jelly, Observable<PeanutButter> peanutButter) {
return Observable.merge(jelly, peanutButter)
.scan(new Sandwich(null, null), (BiFunction<Object, Object, Object>) (prevResult, newItem) -> {
Sandwich prevSandwich = (Sandwich) prevResult;
if (newItem instanceof Jelly) {
System.out.println("emitted: " + ((Jelly) newItem).tag);
return new Sandwich((Jelly) newItem, prevSandwich.peanutButter);
} else {
System.out.println("emitted: " + ((PeanutButter) newItem).tag);
return new Sandwich(prevSandwich.jelly, (PeanutButter) newItem);
}
})
.skip(1) // skip emitting scan's default item
.cast(Sandwich.class);
}
#Test
public void testGetSandwich() {
PublishSubject<Jelly> jelly = PublishSubject.create();
PublishSubject<PeanutButter> peanutButter = PublishSubject.create();
getSandwich(jelly, peanutButter).subscribe(new Observer<Sandwich>() {
#Override
public void onSubscribe(Disposable d) {
System.out.println("onSubscribe");
}
#Override
public void onNext(Sandwich sandwich) {
System.out.println("onNext: Sandwich: " + sandwich.toString());
}
#Override
public void onError(Throwable e) {
System.out.println("onError: " + e.toString());
}
#Override
public void onComplete() {
System.out.println("onComplete");
}
});
jelly.onNext(new Jelly("jelly1"));
jelly.onNext(new Jelly("jelly2"));
peanutButter.onNext(new PeanutButter("peanutButter1"));
jelly.onNext(new Jelly("jelly3"));
peanutButter.onNext(new PeanutButter("peanutButter2"));
}
class Jelly {
String tag;
public Jelly(String tag) {
this.tag = tag;
}
}
class PeanutButter {
String tag;
public PeanutButter(String tag) {
this.tag = tag;
}
}
class Sandwich {
Jelly jelly;
PeanutButter peanutButter;
public Sandwich(Jelly jelly, PeanutButter peanutButter) {
this.jelly = jelly;
this.peanutButter = peanutButter;
}
#Override
public String toString() {
String jellyResult = (jelly != null) ? jelly.tag : "no jelly";
String peanutButterResult = (peanutButter != null) ? peanutButter.tag : "no peanutButter";
return jellyResult + " | " + peanutButterResult;
}
}
}
Output:
onSubscribe
emitted: jelly1
onNext: Sandwich: jelly1 | no peanutButter
emitted: jelly2
onNext: Sandwich: jelly2 | no peanutButter
emitted: peanutButter1
onNext: Sandwich: jelly2 | peanutButter1
emitted: jelly3
onNext: Sandwich: jelly3 | peanutButter1
emitted: peanutButter2
onNext: Sandwich: jelly3 | peanutButter2
The fact that Jelly, PeanutButter and Sandwich are all independent types makes it a bit more complex around casting and nullability in scan. If you have control over these types, this solution can be further improved.

Related

Android + RxJava + For Loop + Not executing all the requests

Caller Of the method,
for (String name : controllerToPartitionModels.keySet())
{
List<PartitionModel> partitionsList = controllerToPartitionModels.get(name);
refreshPartition(partitionsList,false);
}
Method
private void refreshPartition(List<PartitionModel> partitionModels, boolean isSyncAll) {
ITModule.getITService()
.refreshPartitionStatus(new ArrayList<>(partitionModels), isSyncAll)
.subscribeOn(Schedulers.io())
.observeOn(Schedulers.io())
.subscribe(new Action() {
#Override
public void run() throws Exception {
Logger.get().d(ATTActionManager.this, "Refreshing request sent successfully for list of size : " + partitionModels.size());
}
}, (#NonNull Throwable throwable) -> {
Logger.get().d(ATTActionManager.this, "Error on Refresh request");
});
}
Problem
If there are 2 requests that has to be sent, I sometime see only one request being sent. Meaning, even though for loop is executing twice for 2 request(HTTP), I see only one request is being sent to the server.
What is that i am doing wrong here?
Rxjava version in use : 2.2.19
You can merge the above 2 methods to solve your problem by using flatMapIterable.
Merged Solution:
private void refreshPartition(Map<String, ?> controllerToPartitionModels) {
Observable.just(controllerToPartitionModels)
.map(controllerToPartitionModels -> controllerToPartitionModels.keySet())
.flatMapIterable((Function<Set<String>, Iterable<String>>) name -> name)
.map(name -> {
boolean isSyncAll = false; // You can customise as per requirement
return new Pair<List<PartitionModel>, Boolean>(controllerToPartitionModels.get(name), isSyncAll)
})
.flatMap((Function<Pair<List<PartitionModel>, Boolean>, ObservableSource<?>>) pair -> {
boolean isSyncAll = pair.first;
List<PartitionModel> partitionModels = pair.second;
return ITModule.getITService()
.refreshPartitionStatus(new ArrayList<>(partitionModels), isSyncAll)
}
)
.subscribeOn(Schedulers.io())
.observeOn(Schedulers.io())
.subscribe(new Action() {
#Override
public void run() throws Exception {
Logger.get().d(ATTActionManager.this, "Refreshing request sent successfully for list of size : " + partitionModels.size());
}
}, (#NonNull Throwable throwable) -> {
Logger.get().d(ATTActionManager.this, "Error on Refresh request");
});
}
*Kindly replace ? with the valid object type.

How to stop and resume Observable.interval emiting ticks

This will emit a tick every 5 seconds.
Observable.interval(5, TimeUnit.SECONDS, Schedulers.io())
.subscribe(tick -> Log.d(TAG, "tick = "+tick));
To stop it you can use
Schedulers.shutdown();
But then all the Schedulers stops and it is not possible to resume the ticking later. How can I stop and resume the emiting "gracefully"?
Here's one possible solution:
class TickHandler {
private AtomicLong lastTick = new AtomicLong(0L);
private Subscription subscription;
void resume() {
System.out.println("resumed");
subscription = Observable.interval(5, TimeUnit.SECONDS, Schedulers.io())
.map(tick -> lastTick.getAndIncrement())
.subscribe(tick -> System.out.println("tick = " + tick));
}
void stop() {
if (subscription != null && !subscription.isUnsubscribed()) {
System.out.println("stopped");
subscription.unsubscribe();
}
}
}
Some time ago, I was also looking for kind of RX "timer" solutions, but non of them met my expectations. So there you can find my own solution:
AtomicLong elapsedTime = new AtomicLong();
AtomicBoolean resumed = new AtomicBoolean();
AtomicBoolean stopped = new AtomicBoolean();
public Flowable<Long> startTimer() { //Create and starts timper
resumed.set(true);
stopped.set(false);
return Flowable.interval(1, TimeUnit.SECONDS)
.takeWhile(tick -> !stopped.get())
.filter(tick -> resumed.get())
.map(tick -> elapsedTime.addAndGet(1000));
}
public void pauseTimer() {
resumed.set(false);
}
public void resumeTimer() {
resumed.set(true);
}
public void stopTimer() {
stopped.set(true);
}
public void addToTimer(int seconds) {
elapsedTime.addAndGet(seconds * 1000);
}
val switch = new java.util.concurrent.atomic.AtomicBoolean(true)
val tick = new java.util.concurrent.atomic.AtomicLong(0L)
val suspendableObservable =
Observable.
interval(5 seconds).
takeWhile(_ => switch.get()).
repeat.
map(_ => tick.incrementAndGet())
You can set switch to false to suspend the ticking and true to resume it.
Sorry this is in RxJS instead of RxJava, but the concept will be the same. I adapted this from learn-rxjs.io and here it is on codepen.
The idea is that you start out with two streams of click events, startClick$ and stopClick$. Each click occurring on the stopClick$ stream get mapped to an empty observable, and clicks on startClick$ each get mapped to the interval$ stream. The two resulting streams get merge-d together into one observable-of-observables. In other words, a new observable of one of the two types will be emitted from merge each time there's a click. The resulting observable will go through switchMap, which starts listening to this new observable and stops listening to whatever it was listening to before. Switchmap will also start merge the values from this new observable onto its existing stream.
After the switch, scan only ever sees the "increment" value emitted by interval$, and it doesn't see any values when "stop" has been clicked.
And until the first click occurs, startWith will start emitting values from $interval, just to get things going:
const start = 0;
const increment = 1;
const delay = 1000;
const stopButton = document.getElementById('stop');
const startButton = document.getElementById('start');
const startClick$ = Rx.Observable.fromEvent(startButton, 'click');
const stopClick$ = Rx.Observable.fromEvent(stopButton, 'click');
const interval$ = Rx.Observable.interval(delay).mapTo(increment);
const setCounter = newValue => document.getElementById("counter").innerHTML = newValue;
setCounter(start);
const timer$ = Rx.Observable
// a "stop" click will emit an empty observable,
// and a "start" click will emit the interval$ observable.
// These two streams are merged into one observable.
.merge(stopClick$.mapTo(Rx.Observable.empty()),
startClick$.mapTo(interval$))
// until the first click occurs, merge will emit nothing, so
// use the interval$ to start the counter in the meantime
.startWith(interval$)
// whenever a new observable starts, stop listening to the previous
// one and start emitting values from the new one
.switchMap(val => val)
// add the increment emitted by the interval$ stream to the accumulator
.scan((acc, curr) => curr + acc, start)
// start the observable and send results to the DIV
.subscribe((x) => setCounter(x));
And here's the HTML
<html>
<body>
<div id="counter"></div>
<button id="start">
Start
</button>
<button id="stop">
Stop
</button>
</body>
</html>
Here is a another way to do this, I think.
When you check the source code, you will find interval() using class OnSubscribeTimerPeriodically. The key code below.
#Override
public void call(final Subscriber<? super Long> child) {
final Worker worker = scheduler.createWorker();
child.add(worker);
worker.schedulePeriodically(new Action0() {
long counter;
#Override
public void call() {
try {
child.onNext(counter++);
} catch (Throwable e) {
try {
worker.unsubscribe();
} finally {
Exceptions.throwOrReport(e, child);
}
}
}
}, initialDelay, period, unit);
}
So, you will see, if you wanna cannel the loop, what about throwing a new exception in onNext(). Example code below.
Observable.interval(1000, TimeUnit.MILLISECONDS)
.subscribe(new Action1<Long>() {
#Override
public void call(Long aLong) {
Log.i("abc", "onNext");
if (aLong == 5) throw new NullPointerException();
}
}, new Action1<Throwable>() {
#Override
public void call(Throwable throwable) {
Log.i("abc", "onError");
}
}, new Action0() {
#Override
public void call() {
Log.i("abc", "onCompleted");
}
});
Then you will see this:
08-08 11:10:46.008 28146-28181/net.bingyan.test I/abc: onNext
08-08 11:10:47.008 28146-28181/net.bingyan.test I/abc: onNext
08-08 11:10:48.008 28146-28181/net.bingyan.test I/abc: onNext
08-08 11:10:49.008 28146-28181/net.bingyan.test I/abc: onNext
08-08 11:10:50.008 28146-28181/net.bingyan.test I/abc: onNext
08-08 11:10:51.008 28146-28181/net.bingyan.test I/abc: onNext
08-08 11:10:51.018 28146-28181/net.bingyan.test I/abc: onError
You can use takeWhile and loop until conditions is true
Observable.interval(1, TimeUnit.SECONDS)
.takeWhile {
Log.i(TAG, " time " + it)
it != 30L
}
.subscribe(object : Observer<Long> {
override fun onComplete() {
Log.i(TAG, "onComplete " + format.format(System.currentTimeMillis()))
}
override fun onSubscribe(d: Disposable) {
Log.i(TAG, "onSubscribe " + format.format(System.currentTimeMillis()))
}
override fun onNext(t: Long) {
Log.i(TAG, "onNext " + format.format(System.currentTimeMillis()))
}
override fun onError(e: Throwable) {
Log.i(TAG, "onError")
e.printStackTrace()
}
});
#AndroidEx , that's a wonderful answer. I did it a bit differently:
private fun disposeTask() {
if (disposeable != null && !disposeable.isDisposed)
disposeable.dispose()
}
private fun runTask() {
disposeable = Observable.interval(0, 30, TimeUnit.SECONDS)
.flatMap {
apiCall.runTaskFromServer()
.map{
when(it){
is ResponseClass.Success ->{
keepRunningsaidTasks()
}
is ResponseClass.Failure ->{
disposeTask() //this will stop the task in instance of a network failure.
}
}
}

How to rerun CompositeSubscription with ReplaySubject?

I have CompositeSubscription , and there I add Subscription with ReplaySubject
CompositeSubscription compositeSubscription = new CompositeSubscription();
ReplaySubject subject = ReplaySubject.create();
compositeSubscription.add(
manager.getAllContacts()
.toList()
.doOnNext(new Action1<List<Person>>() {
#Override
public void call(List<Person> persons) {
allPersons = persons;
Log.e(TAG, "BookContacts: " + "allPersons = " + allPersons.size());
setupViewPager();
}
})
.subscribe(subject));
then I add second Subscription with this ReplaySubject
compositeSubscription.add(Observable.combineLatest(subject,
(PublishSubject<List<CustomUser>>) execute(
manager.getDigitsContacts()),
new Func2<List<Person>, List<CustomUser>, Object>() {
#Override
public Object call(List<Person> persons, List<CustomUser> customUsers) {
//... my code with persons and customUsers...
return null;
}
})
.subscribe());
code is working, after that complete ReplaySubject hasCompleted = true.
but when I try to add third Subscription , it doesn't call "call()" method
compositeSubscription.add(Observable.combineLatest(subject,
(PublishSubject<List<CustomUser>>) execute(
manager.getFacebookContacts()), //<-----manager.getFacebookContacts() is run, but doesn't call call() method
new Func2<List<Person>, List<CustomUser>, Object>() {
#Override
public Object call(List<Person> persons, List<CustomUser> customUsers) {
//...this method is not called after "manager.getFacebookContacts()"
return null;
}
})
.subscribeOn(Schedulers.newThread())
.subscribe());
HOW TO SOLVE IT?...Because if I add Subscription simultaneously it works fine.
Could you please add error callback to .subscribe()? My guess is that the third time, ReplaySubject overflows the combineLatest's buffer. Instead of creating a subject, you should use .replay().autoConnect(0)
CompositeSubscription compositeSubscription = new CompositeSubscription();
Observable<List<Person>> persons = manager.getAllContacts()
.toList()
.doOnNext(new Action1<List<Person>>() {
#Override
public void call(List<Person> persons) {
allPersons = persons;
Log.e(TAG, "BookContacts: " + "allPersons = " + allPersons.size());
setupViewPager();
}
}).replay().autoConnect(0, s -> compositeSubscription.add(s));
Then use persons instead of subject

Rxjava Android how to use the Zip operator

I am having a lot of trouble understanding the zip operator in RxJava for my android project.
Problem
I need to be able to send a network request to upload a video
Then i need to send a network request to upload a picture to go with it
finally i need to add a description and use the responses from the previous two requests to upload the location urls of the video and picture along with the description to my server.
I assumed that the zip operator would be perfect for this task as I understood we could take the response of two observables (video and picture requests) and use them for my final task.
But I cant seem to get this to occur how I envision it.
I am looking for someone to answer how this can be done conceptually with a bit of psuedo code.
Thank you
Zip operator strictly pairs emitted items from observables. It waits for both (or more) items to arrive then merges them. So yes this would be suitable for your needs.
I would use Func2 to chain the result from the first two observables.
Notice this approach would be simpler if you use Retrofit since its api interface may return an observable. Otherwise you would need to create your own observable.
// assuming each observable returns response in the form of String
Observable<String> movOb = Observable.create(...);
// if you use Retrofit
Observable<String> picOb = RetrofitApiManager.getService().uploadPic(...),
Observable.zip(movOb, picOb, new Func2<String, String, MyResult>() {
#Override
public MyResult call(String movieUploadResponse, String picUploadResponse) {
// analyze both responses, upload them to another server
// and return this method with a MyResult type
return myResult;
}
}
)
// continue chaining this observable with subscriber
// or use it for something else
A small example:
val observableOne = Observable.just("Hello", "World")
val observableTwo = Observable.just("Bye", "Friends")
val zipper = BiFunction<String, String, String> { first, second -> "$first - $second" }
Observable.zip(observableOne, observableTwo, zipper)
.subscribe { println(it) }
This will print:
Hello - Bye
World - Friends
In BiFunction<String, String, String> the first String the type of the first observable, the second String is the type of the second observable, the third String represents the type of the return of your zipper function.
I made a small example that calls two real endpoints using zip in this blog post
Here I have an example that I did using Zip in asynchronous way, just in case you´re curious
/**
* Since every observable into the zip is created to subscribeOn a diferent thread, it´s means all of them will run in parallel.
* By default Rx is not async, only if you explicitly use subscribeOn.
*/
#Test
public void testAsyncZip() {
scheduler = Schedulers.newThread();
scheduler1 = Schedulers.newThread();
scheduler2 = Schedulers.newThread();
long start = System.currentTimeMillis();
Observable.zip(obAsyncString(), obAsyncString1(), obAsyncString2(), (s, s2, s3) -> s.concat(s2)
.concat(s3))
.subscribe(result -> showResult("Async in:", start, result));
}
/**
* In this example the the three observables will be emitted sequentially and the three items will be passed to the pipeline
*/
#Test
public void testZip() {
long start = System.currentTimeMillis();
Observable.zip(obString(), obString1(), obString2(), (s, s2, s3) -> s.concat(s2)
.concat(s3))
.subscribe(result -> showResult("Sync in:", start, result));
}
public void showResult(String transactionType, long start, String result) {
System.out.println(result + " " +
transactionType + String.valueOf(System.currentTimeMillis() - start));
}
public Observable<String> obString() {
return Observable.just("")
.doOnNext(val -> {
System.out.println("Thread " + Thread.currentThread()
.getName());
})
.map(val -> "Hello");
}
public Observable<String> obString1() {
return Observable.just("")
.doOnNext(val -> {
System.out.println("Thread " + Thread.currentThread()
.getName());
})
.map(val -> " World");
}
public Observable<String> obString2() {
return Observable.just("")
.doOnNext(val -> {
System.out.println("Thread " + Thread.currentThread()
.getName());
})
.map(val -> "!");
}
public Observable<String> obAsyncString() {
return Observable.just("")
.observeOn(scheduler)
.doOnNext(val -> {
System.out.println("Thread " + Thread.currentThread()
.getName());
})
.map(val -> "Hello");
}
public Observable<String> obAsyncString1() {
return Observable.just("")
.observeOn(scheduler1)
.doOnNext(val -> {
System.out.println("Thread " + Thread.currentThread()
.getName());
})
.map(val -> " World");
}
public Observable<String> obAsyncString2() {
return Observable.just("")
.observeOn(scheduler2)
.doOnNext(val -> {
System.out.println("Thread " + Thread.currentThread()
.getName());
})
.map(val -> "!");
}
You can see more examples here https://github.com/politrons/reactive
zip operator allow you to compose a result from results of two different observable.
You 'll have to give am lambda that will create a result from datas emitted by each observable.
Observable<MovieResponse> movies = ...
Observable<PictureResponse> picture = ...
Observable<Response> response = movies.zipWith(picture, (movie, pic) -> {
return new Response("description", movie.getName(), pic.getUrl());
});
i have been searching for a simple answer on how to use the Zip operator, and what to do with the Observables i create to pass them to it, i was wondering if i should call subscribe() for every observable or not, non of these answers were simple to find, i had to figure it out by my self, so here is a simple example for using Zip operator on 2 Observables :
#Test
public void zipOperator() throws Exception {
List<Integer> indexes = Arrays.asList(0, 1, 2, 3, 4);
List<String> letters = Arrays.asList("a", "b", "c", "d", "e");
Observable<Integer> indexesObservable = Observable.fromIterable(indexes);
Observable<String> lettersObservable = Observable.fromIterable(letters);
Observable.zip(indexesObservable, lettersObservable, mergeEmittedItems())
.subscribe(printMergedItems());
}
#NonNull
private BiFunction<Integer, String, String> mergeEmittedItems() {
return new BiFunction<Integer, String, String>() {
#Override
public String apply(Integer index, String letter) throws Exception {
return "[" + index + "] " + letter;
}
};
}
#NonNull
private Consumer<String> printMergedItems() {
return new Consumer<String>() {
#Override
public void accept(String s) throws Exception {
System.out.println(s);
}
};
}
the printed result is :
[0] a
[1] b
[2] c
[3] d
[4] e
the final answers to the questions that where in my head were as follows
the Observables passed to the zip() method just need to be created only, they do not need to have any subscribers to them, only creating them is enough ... if you want any observable to run on a scheduler, you can specify this for that Observable ... i also tried the zip() operator on Observables where they should wait for there result, and the Consumable of the zip() was triggered only when both results where ready (which is the expected behavior)
This is my implementation using Single.zip and rxJava2
I tried to make it as easy to understand as possible
//
// API Client Interface
//
#GET(ServicesConstants.API_PREFIX + "questions/{id}/")
Single<Response<ResponseGeneric<List<ResponseQuestion>>>> getBaseQuestions(#Path("id") int personId);
#GET(ServicesConstants.API_PREFIX + "physician/{id}/")
Single<Response<ResponseGeneric<List<ResponsePhysician>>>> getPhysicianInfo(#Path("id") int personId);
//
// API middle layer - NOTE: I had feedback that the Single.create is not needed (but I haven't yet spent the time to improve it)
//
public Single<List<ResponsePhysician>> getPhysicianInfo(int personId) {
return Single.create(subscriber -> {
apiClient.getPhysicianInfo(appId)
.subscribeOn(Schedulers.io())
.observeOn(Schedulers.io())
.subscribe(response -> {
ResponseGeneric<List<ResponsePhysician>> responseBody = response.body();
if(responseBody != null && responseBody.statusCode == 1) {
if (!subscriber.isDisposed()) subscriber.onSuccess(responseBody.data);
} else if(response.body() != null && response.body().status != null ){
if (!subscriber.isDisposed()) subscriber.onError(new Throwable(response.body().status));
} else {
if (!subscriber.isDisposed()) subscriber.onError(new Throwable(response.message()));
}
}, throwable -> {
throwable.printStackTrace();
if(!subscriber.isDisposed()) subscriber.onError(throwable);
});
});
}
public Single<List<ResponseQuestion>> getHealthQuestions(int personId){
return Single.create(subscriber -> {
apiClient.getBaseQuestions(personId)
.subscribeOn(Schedulers.io())
.observeOn(Schedulers.io())
.subscribe(response -> {
ResponseGeneric<List<ResponseQuestion>> responseBody = response.body();
if(responseBody != null && responseBody.data != null) {
if (!subscriber.isDisposed()) subscriber.onSuccess(response.body().data);
} else if(response.body() != null && response.body().status != null ){
if (!subscriber.isDisposed()) subscriber.onError(new Throwable(response.body().status));
} else {
if (!subscriber.isDisposed()) subscriber.onError(new Throwable(response.message()));
}
}, throwable -> {
throwable.printStackTrace();
if(!subscriber.isDisposed()) subscriber.onError(throwable);
});
});
}
//please note that ResponseGeneric is just an outer wrapper of the returned data - common to all API's in this project
public class ResponseGeneric<T> {
#SerializedName("Status")
public String status;
#SerializedName("StatusCode")
public float statusCode;
#SerializedName("Data")
public T data;
}
//
// API end-use layer - this gets close to the UI so notice the oberver is set for main thread
//
private static class MergedResponse{// this is just a POJO to store all the responses in one object
public List<ResponseQuestion> listQuestions;
public List<ResponsePhysician> listPhysicians;
public MergedResponse(List<ResponseQuestion> listQuestions, List<ResponsePhysician> listPhysicians){
this.listQuestions = listQuestions;
this.listPhysicians = listPhysicians;
}
}
// example of Single.zip() - calls getHealthQuestions() and getPhysicianInfo() from API Middle Layer
private void downloadHealthQuestions(int personId) {
addRxSubscription(Single
.zip(getHealthQuestions(personId), getPhysicianInfo(personId), MergedResponse::new)
.subscribeOn(Schedulers.io())
.observeOn(AndroidSchedulers.mainThread())
.subscribe(response -> {
if(response != null) {
Timber.i(" - total health questions downloaded %d", response.listQuestions.size());
Timber.i(" - physicians downloaded %d", response.listPhysicians.size());
if (response.listPhysicians != null && response.listPhysicians.size()>0) {
// do your stuff to process response data
}
if (response.listQuestions != null && response.listQuestions.size()>0) {
// do your stuff to process response data
}
} else {
// process error - show message
}
}, error -> {
// process error - show network error message
}));
}
You use the zip from rxjava with Java 8:
Observable<MovieResponse> movies = ...
Observable<PictureResponse> picture = ...
Observable<ZipResponse> response = Observable.zip(movies, picture, ZipResponse::new);
class ZipResponse {
private MovieResponse movieResponse;
private PictureResponse pictureResponse;
ZipResponse(MovieResponse movieResponse, PictureResponse pictureResponse) {
this.movieResponse = movieResponse;
this.pictureResponse = pictureResponse;
}
public MovieResponse getMovieResponse() {
return movieResponse;
}
public void setMovieResponse(MovieResponse movieResponse) {
this.movieResponse= movieResponse;
}
public PictureResponse getPictureResponse() {
return pictureResponse;
}
public void setPictureResponse(PictureResponse pictureResponse) {
this.pictureResponse= pictureResponse;
}
}
You can use .zipWith operator for Observable chains.
If uploadMovies() and uploadPictures() return Observable,
uploadMovies()
.zipWith(uploadPictures()) { m, p ->
"$m with $p were uploaded"
}
.subscribe { print(it) }

RxAndroid, combining multiple web calls

public List<Office> getOffices(){
final List<Office> offices = new ArrayList<>();
Observable observable = Observable.create(new Observable.OnSubscribe<Object>() {
#Override
public void call(Subscriber<? super Object> subscriber) {
for(String[] of : backToArray(downloadWebPage("http://api.ataxcloudapp.com/v1/franchise/listing/?location=" + zip))) {
offices.add(
new Office(
of,
backToArray(downloadWebPage("http://api.ataxcloudapp.com/v1/franchise/details/hours/" + of[0])).get(0),
downloadImage("https://www.ataxcloudapp.com/WebShared/uploads/franchises/" + of[0] + "/manager-photo.jpg?404=picture-placeholder.jpg"),
downloadImage("https://maps.googleapis.com/maps/api/staticmap?center=" + of[12] + ","+ of[13] +"&zoom=12&size=300x150&maptype=roadmap")
)
);
}
subscriber.onCompleted();
}
});
observable.subscribeOn(Schedulers.newThread())
.observeOn(AndroidSchedulers.mainThread())
.subscribe();
return offices;
}
The above solution kinda works, it takes very long to load results and its not consistent. the last 3 calls are all dependent on information given in the first call. What am i doing wrong here?
First, note that in order to be able to compose async methods, they all should return Observable<Something> and not directly Something.
So you should change your download methods to
public Observable<Image> downloadImage(String url)
public Observable<WebPage> downloadWebPage(String url)
Or create wrapper methods around them if you cannot change them.
Then you can use flatMap and zip for the getOffices method:
public Observable<Office> getOffices() {
return downloadWebPage("office-url")
.flatMap(new Func1<WebPage, Observable<Office>>() {
public Observable<Office> call(WebPage webPage) {
String url1 = "blah" + webPage.getInfo1();
String url2 = "blah" + webPage.getInfo2();
String url3 = "blah" + webPage.getInfo3();
return Observable.zip(
downloadWebPage(url1),
downloadImage(url2),
downloadImage(url3),
new Func3<WebPage, Image, Image, Office>() {
public Office call(WebPage p, Image img1, Image img2) {
return new Office(p.getInfo0(), img1, img2);
}
});
}
});
}

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