Questions tagged [rx-java2]
anything related to RxJava2 – The new implementation of the RxJava Reactive Extensions for the JVM – a library for composing asynchronous and event-based programs using observable sequences for the Java VM.
4,116
questions
229
votes
10
answers
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When to use RxJava in Android and when to use LiveData from Android Architectural Components?
I am not getting the reason to use RxJava in Android and LiveData from Android Architectural Components.It would be really helpful if the usecases and differences between the both are explained along ...
- 2,413
152
votes
8
answers
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The result of subscribe is not used
I've upgraded to Android Studio 3.1 today, which seems to have added a few more lint checks. One of these lint checks is for one-shot RxJava2 subscribe() calls that are not stored in a variable. For ...
- 9,747
136
votes
3
answers
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What is the difference between Observable, Completable and Single in RxJava
Can anyone please explain the difference between Observable, Completable and Single in RxJava with clear examples?
In which scenario we use one over the others?
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107
votes
3
answers
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Unable to create call adapter for io.reactivex.Observable
I'm going to send a simple get method to my server(it is Rails app) and get the result using RxJava and Retrofit. The thing that I did is:
My interface:
public interface ApiCall {
String ...
- 2,210
96
votes
6
answers
30k
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Rxandroid What's the difference between SubscribeOn and ObserveOn
I am just learning Rx-java and Rxandroid2 and I am just confused what is the major difference between in SubscribeOn and ObserveOn.
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80
votes
3
answers
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How to use CompositeDisposable of RxJava 2?
In RxJava 1, there was CompositeSubscription, but that is not present in RxJava2, There is something CompositeDisposable in rxJava2. How do I use CompositeDisposable or Disposable in RxJava2?
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79
votes
5
answers
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How to chain two Completable in RxJava2
I have two Completable. I would like to do following scenario:
If first Completable gets to onComplete , continue with second Completable. The final results would be onComplete of second Completable.
...
- 9,042
78
votes
7
answers
32k
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Cannot resolve symbol InstantTaskExecutorRule
I open example code BasicRxJavaSample (from this article Room+RxJava)
The main thing is there:
@Rule
public InstantTaskExecutorRule instantTaskExecutorRule =
new InstantTaskExecutorRule();
And ...
- 2,636
73
votes
4
answers
16k
views
Difference between RxJava API and the Java 9 Flow API
It seems on every iteration of Java for the last few major releases, there are consistently new ways to manage concurrent tasks.
In Java 9, we have the Flow API which resembles the Flowable API of ...
- 7,552
71
votes
10
answers
37k
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Android RxJava 2 JUnit test - getMainLooper in android.os.Looper not mocked RuntimeException
I am encountering a RuntimeException when attempting to run JUnit tests for a presenter that is using observeOn(AndroidSchedulers.mainThread()).
Since they are pure JUnit tests and not Android ...
- 11.2k
62
votes
3
answers
31k
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When to call dispose and clear on CompositeDisposable
My question can be a duplicate of How to use CompositeDisposable of RxJava 2? But asking to clear one more doubt.
According to the accepted answer
// Using clear will clear all, but can accept new ...
user4260260
52
votes
1
answer
18k
views
Subscribewith Vs subscribe in RxJava2(Android)?
When to call the subscribeWith method rather than plain subscribe? And what is the use case?
compositeDisposable.add(get()
.observeOn(AndroidSchedulers.mainThread())
.subscribeOn(Schedulers....
- 5,505
42
votes
6
answers
31k
views
Reactive Programming Advantages/Disadvantages
I keep studying and trying Reactive Style of coding using Reactor and RxJava. I do understand that reactive coding makes better utilization of CPU compared to single threaded execution.
Is there any ...
- 1,579
41
votes
4
answers
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RxJava2 observable take throws UndeliverableException
As I understand RxJava2 values.take(1) creates another Observable that contains only one element from the original Observable. Which MUST NOT throw an exception as it is filtered out by the effect of ...
- 1,263
41
votes
6
answers
15k
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RxJava 2.x: Should I use Flowable or Single/Completable?
I'm developing an Android app using Clean Architecture and I'm migrating it to RxJava 2.x. I have to make some network requests to a soap service, so I defined the api interface in the domain module:
...
37
votes
4
answers
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RxJava Single.just() vs Single.fromCallable()?
I wondered if someone can shed some light on this question, when to use
Single.fromCallable( ()-> myObject )
instead of
Single.just(myObject)
from the documentation, Single.fromCallable():
/...
- 5,505
35
votes
2
answers
12k
views
Do I have to unsubscribe from completed observable?
If an observable completes, do I still have to unsubscribe / dispose (in RxJava2) the observable to remove the Observer (prevent memory leaks) or is this handled internally by RxJava once a onComplete ...
- 15.2k
34
votes
5
answers
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How to convert rxJava2's Observable to Completable?
I have Observable stream, and I want to convert it to Completable, how I could do that?
- 4,591
33
votes
6
answers
29k
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RxJava flatMapIterable with a Single
I'm trying to tidy up my code a little, and Single is looking like a good choice for me as I'm doing something that will only ever emit one result.
I'm having an issue though as I was using ...
- 388
33
votes
2
answers
20k
views
Is there something like Single.empty()
I'm in the process of migrating from Rx 1 to Rx 2 and suddenly while reading through posts I found out that Single should be the type of observable to use for retrofit calls.
So I've decided to give ...
- 15.3k
32
votes
6
answers
50k
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How to reset a BehaviorSubject
I have a BehaviorSubject that I would like to reset - by that I mean I want the latest value to not be available, just as if it was just created.
I don't seem to see an API to do this but I suppose ...
- 10.6k
31
votes
1
answer
14k
views
Difference between doAfterTerminate and doFinally
Does anybody knows what is the difference between operators "doAfterTerminate" and "doFinally" in RxJava 2 ?
- 24.8k
29
votes
5
answers
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Cannot resolve symbol AndroidSchedulers
I'm using version 2.0.0 of RxJava, and it seems like I have no access to AndroidSchedulers. I'm unable to get access to mainthread through RxJava
- 557
28
votes
3
answers
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Which rxjava3 retrofit-adapter should we use for Rxjava3
I am using RxJava3 and retrofit but I am unable to get a rxjava3 retrofit-adapter for RxJava3.
- 1,220
28
votes
2
answers
16k
views
RxJava `Completable.andThen` is not executing serially?
I have a usecase where I initiallize some global variables in a Completable , and in the next step in the chain (using andThen operator) I make use of those variables.
Following sample explains my ...
- 921
28
votes
3
answers
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views
RxJavaPlugins Error Didn't find class "com.google.devtools.build.android.desugar.runtime.ThrowableExtension"
After upgrading Android Studio 3.0 Beta 1 getting the following error.
When I downgraded the error disappeared.
Studio Build: Android Studio 3.0 Beta 1
Version of Gradle Plugin: 'com.android....
- 1,195
28
votes
4
answers
17k
views
Best practice for disposing Completable, Single, Maybe and terminating Observables in RxJava
I'm asking this from an Android perspective, but this should apply to RxJava in general.
As a best practice, should my view always dispose of even short lived Completable, Single, Maybe and ...
- 8,809
26
votes
3
answers
15k
views
Convert RxJava Observables To Live Data With Kotlin Extension Functions
I've been using alot of RxJava Observables converted to LiveData in my code using LiveDataReactiveStreams.fromPublisher() library. So I though of adding an extension function to the RxJava Observable ...
- 9,406
26
votes
3
answers
15k
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How to convert a List<Object> to PagedList<Object> and vice-versa?
PagedList<Object> is used for Android's cool paging library. To make the question as minimal as possible :
If i have a list of strings like
List<String> stringList; // it consists of ...
- 10.2k
25
votes
2
answers
14k
views
Observable.combineLatest type inference in kotlin
I'm using RxJava2, Kotlin-1.1 along with RxBindings in my project.
I have simple login screen with 'login' button disabled by default, I want to enable the button only when username and password ...
- 5,225
25
votes
4
answers
3k
views
What's the difference between curly braces and normal brackets in RxJava with Kotlin
I don't understand the real difference between the curly braces and and the normal brackets in Kotlin when using RxJava. For example, I have the following code which works as expected:
...
- 10.5k
24
votes
2
answers
9k
views
What is the difference between RxJava 2 Cancellable and Disposable?
I want to create an Observable from view click listener using RxJava 2. I started from the simplest implementation (I don't use lambdas here to show you different types in this method):
Observable&...
- 6,185
24
votes
2
answers
4k
views
Can't subscribe on a RxJava 2 Observable with TestSubscriber
Why is my compiler not allowing myself to subscribe on an Observable with a TestSubscriber?
Here's my code:
TestSubscriber<User> testSubscriber = new TestSubscriber<>();
Observable.just(...
- 1,053
23
votes
4
answers
10k
views
Handle empty response with retrofit and rxjava 2.x
When using rxjava 1.x i used to return Observable<Void> to handle empty response from retrofit:
@POST( "login" )
Observable<Void> getToken( @Header( "Authorization" ) String authorization,...
- 4,414
23
votes
2
answers
26k
views
How to use "if-else" in RX java chain?
I am a newer on RXJava/RXAndroid. I want to implement this case: chose different way based on some condition in RXJava.
For example, first, I fetch user info from network and if this is a VIP user, I ...
- 327
23
votes
1
answer
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views
How to do a single row query with Android Room
How do I make a single row query with Android Room with RxJava? I am able to query for List of items, no issues. Here, I want to find if a specific row exists. According to the docs, looks like I can ...
- 1,620
21
votes
4
answers
18k
views
How to handel no results with Android Room and RxJava 2?
I have database with table contact and I want to check if there is contact with some phone number.
@Query("SELECT * FROM contact WHERE phone_number = :number")
Flowable<Contact> ...
- 2,605
21
votes
5
answers
6k
views
Synchronous or Asynchronous Rxjava inside the Worker (from WorkManager component) what's the right choice?
I'm new to the new architecture component WorkManager, I do my API calls via Retrofit and RxJava.
My use case here is to get new posts from the Backend, then show notification, and update a widget.
...
- 3,525
21
votes
7
answers
27k
views
How to pass null to an Observable with nullable type in RxJava 2 and Kotlin
I initialize my variable like this:-
val user: BehaviorSubject<User?> user = BehaviorSubject.create()
But I can't do this. IDE throws an error:-
user.onNext(null)
And doing this, IDE says u ...
- 948
21
votes
1
answer
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views
RxJava 2.0 - How to convert Observable to Publisher
How to convert Observable to Publisher in RxJava version 2?
In the first version we have the https://github.com/ReactiveX/RxJavaReactiveStreams project that do exactly what I need.
But How can I do ...
- 346
20
votes
1
answer
8k
views
Run void method in background
I want to run a method in background using rxjava. I don't care about the result.
void myHeavyMethod() { (...) }
So far the only solution I have is to modify the return type to e.g. boolean.
...
- 5,146
20
votes
2
answers
12k
views
RxJava Scheduler to observe on main thread
If I write something like this, then both the operation and notification will be on the current thread...
Observable.fromCallable(() -> "Do Something")
.subscribe(System.out::println);
If I ...
- 7,850
19
votes
4
answers
19k
views
Method getMainLooper in android.os.Looper not mocked still occuring even after adding RxImmediateSchedulerRule
TrendingViewModelTest
@RunWith(JUnit4::class)
class TrendingViewModelTest {
private lateinit var trendingRepository: TrendingRepository
private lateinit var trendingViewModel: ...
- 8,168
19
votes
1
answer
7k
views
How does backpressure work in Project Reactor?
I've been working in Spring Reactor and had some previous testing that made me wonder how Fluxes handle backpressure by default. I know that onBackpressureBuffer and such exist, and I have also read ...
- 297
19
votes
4
answers
8k
views
Android Dagger2 + OkHttp + Retrofit dependency cycle error
Hey there I am using Dagger2, Retrofit and OkHttp and I am facing dependency cycle issue.
When providing OkHttp :
@Provides
@ApplicationScope
OkHttpClient provideOkHttpClient(TokenAuthenticator ...
- 6,305
19
votes
1
answer
5k
views
Paging3: "Not sure how to convert a Cursor to this method's return type" when using PagingSource as return type in Room DAO
I was trying to imitate Google's codelab for the new Paging 3 library, and I encountered the following error when I tried to have a Room DAO method return a PagingSource:
D:\Programming\Android\...
- 1,521
19
votes
4
answers
8k
views
RxJava Relay vs Subjects
I'm trying to understand the purpose of this library by Jake Warthon:
https://github.com/JakeWharton/RxRelay
Basically: A Subject except without the ability to call onComplete or
onError. ...
- 12.6k
18
votes
1
answer
10k
views
Handling Error RXJava Android with Kotlin
Hi I'm new with RxJava and Kotlin and I loose some concepts about it.
I have "api" like this:
interface VehiclesService {
@GET("/vehicles/")
fun getVehicles(): Single<List<Vehicle>&...
- 7,486
18
votes
2
answers
11k
views
Chain Completable into Observable flow
Suppose you want to insert a Completable in your Observable chain, such as for each emitted element, there is a completable that runs and blocks until it completes, what option would you choose? (here ...
- 711
18
votes
2
answers
17k
views
Retrofit 2 + RxJava cancel/unsubscribe
I am performing a network request where I send files and a message.
I would like to have an option to cancel current request. I have found two similar questions and both suggests that observable....
- 1,651