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RxJava return error as onNext and continue stream

so i tried to use onErrorReturn to return the result that i wanted but it will complete the stream afterwards, how do i catch the error return as Next and still continue the stream?
with code below, it wont reach retryWhen when there is error and if i flip it around it wont re-subscribe with retryWhen if there is an error
fun process(): Observable<State> {
return publishSubject
.flatMap { intent ->
actAsRepo(intent) // Might return error
.map { State(data = it, error = null) }
}
.onErrorReturn { State(data = "", error = it) } // catch the error
.retryWhen { errorObs ->
errorObs.flatMap {
Observable.just(State.defaultState()) // continue subscribing
}
}
}
private fun actAsRepo(string: String): Observable<String> {
if (string.contains('A')) {
throw IllegalArgumentException("Contains A")
} else {
return Observable.just("Wrapped from repo: $string")
}
}
subscriber will be
viewModel.process().subscribe(this::render)

onError is a terminal operator. If an onError happens, it will be passed along from operator to operator. You could use an onError-operator which catches the onError and provides a fallback.
In your example the onError happens in the inner-stream of the flatMap. The onError will be propagated downstream to the onErrorReturn opreator. If you look at the implementation, you will see that the onErrorReturn lambda will be invoked, the result will be pushed downstream with onNext following a onComplete
#Override
public void onError(Throwable t) {
T v;
try {
v = valueSupplier.apply(t);
} catch (Throwable e) {
Exceptions.throwIfFatal(e);
downstream.onError(new CompositeException(t, e));
return;
}
if (v == null) {
NullPointerException e = new NullPointerException("The supplied value is null");
e.initCause(t);
downstream.onError(e);
return;
}
downstream.onNext(v); // <--------
downstream.onComplete(); // <--------
}
What is the result of your solution?
Your stream completes because of: #retryWhen JavaDoc
If the upstream to the operator is asynchronous, signalling onNext followed by onComplete immediately may result in the sequence to be completed immediately. Similarly, if this inner {#code ObservableSource} signals {#code onError} or {#code onComplete} while the upstream is active, the sequence is terminated with the same signal immediately.
What you ought to do:
Place the onErrorReturn behind the map opreator in the flatMap. With this ordering your stream will not complete, when the inner-flatMap stream onErrors.
Why is this?
The flatMap operator completes, when the outer (source: publishSubject) and the inner stream (subscription) both complete. In this case the outer stream (publishSubject) emits onNext and the inner-stream will complete after sending { State(data = "", error = it) } via onNext. Therefore the stream will remain open.
interface ApiCall {
fun call(s: String): Observable<String>
}
class ApiCallImpl : ApiCall {
override fun call(s: String): Observable<String> {
// important: warp call into observable, that the exception is caught and emitted as onError downstream
return Observable.fromCallable {
if (s.contains('A')) {
throw IllegalArgumentException("Contains A")
} else {
s
}
}
}
}
data class State(val data: String, val err: Throwable? = null)
apiCallImpl.call will return an lazy observable, which will throw an error on subscription, not at observable assembly time.
// no need for retryWhen here, except you want to catch onComplete from the publishSubject, but once the publishSubject completes no re-subscription will help you, because the publish-subject is terminated and onNext invocations will not be accepted anymore (see implementation).
fun process(): Observable<State> {
return publishSubject
.flatMap { intent ->
apiCallImpl.call(intent) // Might return error
.map { State(data = it, err = null) }
.onErrorReturn { State("", err = it) }
}
}
Test
lateinit var publishSubject: PublishSubject<String>
lateinit var apiCallImpl: ApiCallImpl
#Before
fun init() {
publishSubject = PublishSubject.create()
apiCallImpl = ApiCallImpl()
}
#Test
fun myTest() {
val test = process().test()
publishSubject.onNext("test")
publishSubject.onNext("A")
publishSubject.onNext("test2")
test.assertNotComplete()
.assertNoErrors()
.assertValueCount(3)
.assertValueAt(0) {
assertThat(it).isEqualTo(State("test", null))
true
}
.assertValueAt(1) {
assertThat(it.data).isEmpty()
assertThat(it.err).isExactlyInstanceOf(IllegalArgumentException::class.java)
true
}
.assertValueAt(2) {
assertThat(it).isEqualTo(State("test2", null))
true
}
}
Alternative
This alternative behaves a little bit different, than the first solution. The flatMap-Operator takes a boolean (delayError), which will result in swallowing onError messages, until the sources completes. When the source completes, the errors will be emitted.
You may use delayError true, when the exception is of no use and must not be logged at the time of appearance
process
fun process(): Observable<State> {
return publishSubject
.flatMap({ intent ->
apiCallImpl.call(intent)
.map { State(data = it, err = null) }
}, true)
}
Test
Only two values are emitted. The error will not be transformed to a fallback value.
#Test
fun myTest() {
val test = process().test()
publishSubject.onNext("test")
publishSubject.onNext("A")
publishSubject.onNext("test2")
test.assertNotComplete()
.assertNoErrors()
.assertValueAt(0) {
assertThat(it).isEqualTo(State("test", null))
true
}
.assertValueAt(1) {
assertThat(it).isEqualTo(State("test2", null))
true
}
.assertValueCount(2)
}
NOTE: I think you want to use switchMap in this case, instead of flatMap.

Chaining Calls on RxJava

There are cases when I need to chain RxJava calls.
The simplest one:
ViewModel:
fun onResetPassword(email: String) {
...
val subscription = mTokenRepository.resetPassword(email)
.observeOn(AndroidSchedulers.mainThread())
.subscribeOn(Schedulers.io())
.subscribe(
//UI update calls
)
...
}
My Repository:
fun resetPassword(email: String): Single<ResetPassword> {
return Single.create { emitter ->
val subscription = mSomeApiInterface.resetPassword(email)
.observeOn(AndroidSchedulers.mainThread())
.subscribeOn(Schedulers.io())
.subscribe({
emitter.onSuccess(...)
}, { throwable ->
emitter.onError(throwable)
})
...
}
}
My Question
Do I need to Add:
.observeOn(AndroidSchedulers.mainThread())
.subscribeOn(Schedulers.io())
for both calls to avoid any app freeze? or the second one for API call is enough?

No, you don't need to add
.observeOn(AndroidSchedulers.mainThread())
.subscribeOn(Schedulers.io())
for the repo and the viewmodel.
.observeOn usually should be called right before handling the ui rendering. So usually, you'll need it in the ViewModel right before updating the ui or emitting the LiveData values.
Also, you properly don't need to subscribe to mSomeApiInterface in your repo, I think it would be better off to just return in as it's from your method up the chain, somthing like this:
fun resetPassword(email: String): Single<ResetPassword> {
return mSomeApiInterface.resetPassword(email);
}
and if you have any mapping needed you can chain it normally
fun resetPassword(email: String): Single<ResetPassword> {
return mSomeApiInterface.resetPassword(email)
.map{it -> }
}
This way you can write your ViewModel code as follow
fun onResetPassword(email: String) {
...
// note the switcing between subscribeOn and observeOn
// the switching is in short: subscribeOn affects the upstream,
// while observeOn affects the downstream.
// So we want to do the work on IO thread, then deliver results
// back to the mainThread.
val subscription = mTokenRepository.resetPassword(email)
.subscribeOn(Schedulers.io())
.observeOn(AndroidSchedulers.mainThread())
.subscribe(
//UI update calls
)
...
}
This will run the API request on the io thread, will returning the result on the mainThread, which is probably what you want. :)
This artical has some good examples and explanations for subscribeOn and observeOn, I strongly recommend checking it.

Observable<RequestFriendModel> folderAllCall = service.getUserRequestslist(urls.toString());
folderAllCall.subscribeOn(Schedulers.io())
.observeOn(AndroidSchedulers.mainThread())
.map(result -> result.getRequested())
.subscribe(this::handleResults, this::handleError);
private void handleResults(List<Requested> folderList) {
if (folderList != null && folderList.size() != 0) {
usersList.addAll(folderList);
}
adapter.notifyDataSetChanged();
}
}
private void handleError(Throwable t) {
Toast.makeText(getContext(),t.getMessage(),Toast.LENGTH_LONG).show();
}
in interface:
#Headers({ "Content-Type: application/json;charset=UTF-8"})
#GET
Observable<RequestFriendModel> getUserRequestslist(#Url String url);
POJO model :
public class RequestFriendModel {
#SerializedName("requested")
#Expose
private List<Requested> requested = null;
public List<Requested> getRequested() {
return requested;
}
public void setRequested(List<Requested> requested) {
this.requested = requested;
}
}

onError is called instead of onNext on 200 network response - RxJava, Retrofit

As mentioned in the title onNext is not called when request responds with 200. It fires onError instead. LogCat doesn't show any errors. I am also sure that HTTP request responds with 200.
Here is my service interface
interface EnrollmentService {
#POST("enrollment/precheck")
fun sendPhoneNumber(#Body phoneInput: PhoneInputRequest) : Observable<Void>
}
Repository
class EnrollmentRepository(api : Retrofit) : BaseRepository(api) {
private val service = api.create(EnrollmentService::class.java)
fun sendPhoneNumber(phoneInputRequest: PhoneInputRequest) = service.sendPhoneNumber(phoneInputRequest)
}
And here is the method in the ViewModel that fires request:
fun sendPhoneNumber(phoneNumber: String) {
if(!isNetworkAvailable(phoneInputResponse))
return
compositeDisposable.add(repository.sendPhoneNumber(PhoneInputRequest(PhoneNumber("+48", phoneNumber)))
.subscribeOn(Schedulers.io())
.observeOn(AndroidSchedulers.mainThread())
.subscribe(
{ phoneInputResponse.postValue(Event(ApiResponse.success(null)))},
{error -> phoneInputResponse.postValue(Event(ApiResponse.error(ResponseError.getErrorType(error)))) }
))
}

If you are just expecting response.code() change the return type of the sendPhoneNumber method to Observable<Response<Void>> from Observable<Void>
So, use :-
fun sendPhoneNumber(#Body phoneInput: PhoneInputRequest) : Observable<Response<Void>>

How to gey body() response using RxJava in Android

I am new to Kotlin and I am making a method that makes a call to an interface of Endpoints and uses one of the methods present there. I am using Observable<> instead of Call<> into the response. I wanted to know how to obtain the response body() in the "result" above. This is my method
private fun refreshUser(userLogin: String) {
executor.execute {
// Check if user was fetched recently
val userExists = userDao.hasUser(userLogin, getMaxRefreshTime(Date())) != null
// If user have to be updated
if (!userExists) {
disposable = endpoints.getUser(userLogin)
.subscribeOn(Schedulers.io())
.observeOn(AndroidSchedulers.mainThread())
.subscribe(
{ result -> /*Get the response body() HERE*/},
{ error -> Log.e("ERROR", error.message) }
)
}
}
}

It all depends on how you have defined the Retrofit interface. In order to get the Response you need to return something from the interface that looks like:
fun getUsers() : Observable<Response<User>>
Then inside { result -> /*Get the response body() HERE*/}, you will get something of the form Response<User>, which has the response's body.
Also to note, you do not need to enclosing executor if you leverage Room for the dao interactions; it has RxJava support. You can use RxJava operators to combine the dao lookup with the server call.

See this tutorial
https://medium.freecodecamp.org/rxandroid-and-kotlin-part-1-f0382dc26ed8
//Kotlin
Observable.just("Hello World")
.subscribeOn(Schedulers.newThread())
//each subscription is going to be on a new thread.
.observeOn(AndroidSchedulers.mainThread()))
//observation on the main thread
//Now our subscriber!
.subscribe(object:Subscriber<String>(){
override fun onCompleted() {
//Completed
}
override fun onError(e: Throwable?) {
//TODO : Handle error here
}
override fun onNext(t: String?) {
Log.e("Output",t);
}
})
if you wanna use retrofit 2 and rxjava 2
https://medium.com/#elye.project/kotlin-and-retrofit-2-tutorial-with-working-codes-333a4422a890
interface WikiApiService {
#GET("api.php")
fun hitCountCheck(#Query("action") action: String,
#Query("format") format: String,
#Query("list") list: String,
#Query("srsearch") srsearch: String):
Observable<Model.Result>
}
Observable is the class response.
private fun beginSearch(srsearch: String) {
disposable =
wikiApiServe.hitCountCheck("query", "json", "search", srsearch)
.subscribeOn(Schedulers.io())
.observeOn(AndroidSchedulers.mainThread())
.subscribe(
{ result -> showResult(result.query.searchinfo.totalhits) },
{ error -> showError(error.message) }
)
}

If, as you mentioned to #Emmanuel, the return type of your getUser() method is Observable<Response<User>> then calling result.body() will yield the resulting User.
{ result ->
val user: User = result.body()
}
If however, you are looking for the the raw response, you can instead call result.raw().body(); which will return an okhttp3.ResponseBody type.
{ result ->
val body: ResponseBody = result.raw().body()
val text: String = body.string()
}

Poll second URL until JSON returns an expected parameter

I'm using a travel API which I first hit with a request to create a session and then I use the session URL returned from that URL to then call until its status parameter returns UpdatesComplete.
Here's what I have so far:
lateinit var pollUrl: String
travelInteractor.createSession("LHR", "AKL", "2018-04-20", "2018-04-22")
.doOnSubscribe {
loading.postValue(true)
}
.flatMap { url ->
pollUrl = url
travelInteractor.pollResults(pollUrl)
.retryWhen {
it.delay(1000, TimeUnit.MILLISECONDS)
}
}
.doOnNext {
if (it.status != "UpdatesComplete") travelInteractor.pollResults(pollUrl)
.retryWhen {
it.delay(1000, TimeUnit.MILLISECONDS)
}
}
.subscribe({
// Subscription stuff
)}
What's currently happening is that it will call doOnNext() and then it will make the network poll but I won't be capturing the subscription and also won't chain another poll. Is there a more efficient way I can be writing this?
Solution
Thanks to iagreen I managed to achieve this with:
lateinit var pollUrl: String
travelInteractor.createSession("LHR", "AKL", "2018-04-20", "2018-04-22")
.doOnSubscribe {
loading.postValue(true)
}
.flatMap { url ->
travelInteractor.pollResults(url)
.retryWhen {
it.delay(1000, TimeUnit.MILLISECONDS)
}
.repeatWhen {
it.delay(1000, TimeUnit.MILLISECONDS)
}
.filter {
it.itineraries.map { ... } // Use response here appropriately and then check status
it.status == "UpdatesComplete"
}
.take(1)
}
.subscribe({
// Subscription stuff
)}

I am assuming your pollResults(url) method returns a Single or an Observable that behaves like a single -- it returns one result and then onComplete. If that is truly the case, you can use repeatWhen to retry the request on success and retryWhen to retry on error. See the code below.
skyScannerInteractor.createSession("LHR", "AKL", "2018-04-20", "2018-04-22")
.doOnSubscribe {
loading.postValue(true)
}
.flatMap { url ->
skyScannerInteractor.pollResults(url)
.repeatWhen { complete -> complete.delay(1, TimeUnit.SECONDS) }
.retryWhen { errors -> errors.delay(1, TimeUnit.SECONDS) }
.filter({ it.status == "UpdatesComplete" })
.take(1) // Take the first valid value and complete
}
.subscribe({
// Subscription stuff
)}
A little explanation -
repeatWhen/retryWhen will try the request every second.
filter will cause elements with the wrong status to be ignored.
When you get the first status == "UpdatesComplete" element, take(1) will emit that value and complete -- this will have the effect of cancelling the retries.
Note: In the case of an error, retrying a network request forever is usually the wrong thing to do. I recommend you modify the retryWhen above to suit you use case to terminate in the event of network failure. For example, you could retry three times and then propagate the error. See this article for some examples on how you could do that. It is also a good reference on repeatWhen/retryWhen.

retry() and retryWhen() both respond to an onError event in the Observable, that is why it isn't actually retrying; you're not receiving those onError events in your pollResults() Observable. Right now, your retrying code doesn't actually depend on the JSON response.
There are two ways I would think about going about this:
Throw an exception in your pollResults() Observable if the JSON response is unsatisfactory. This should trigger the retryWhen(). You'll need to test for it in the Observable somewhere.
Reorganize your Observable like this:
`
lateinit var pollUrl: String
skyScannerInteractor.createSession("LHR", "AKL", "2018-04-20", "2018-04-22")
.doOnSubscribe {
loading.postValue(true)
}
.flatMap { url ->
pollUrl = url
skyScannerInteractor.pollResults(pollUrl)
}
.doOnNext {
if (it.status != "UpdatesComplete") {
throw IOException("Updates not complete.") //Trigger onError
}
}
.retryWhen { //Retry the Observable (createSession) when onError is called
it.delay(1000, TimeUnit.MILLISECONDS)
}
.subscribe({
// Will give result only when UpdatesComplete
}