Cant 'observeOn' main thread with RxKotlin

Question

I'm trying to observe observable on main thread by using:

    // Kotlin Code
    Observable
      .observeOn(AndroidSchedulers.mainThread())

but I'm getting following error:

    Type Mismatch:
      Required: rx.Scheduler!
      Found: io.reactivex.Scheduler!

The Observable I'm subscribing to is from a Library that is written in Java and therefore uses RxJava.

Am i being stupid and missing something? I'm puzzeled :$

Thanks in advance :)

Tutorial

github.com/ReactiveX/RxAndroid/issues/348 might this help? What's your rx related imports? – Phosgenite

Thanks, @Ascorbin. That issue post did help and I realised that the library I was using imported 'rx.Observable', so I changed it to 'io.reactivex.Observable' but that hasn't solved the issue. – Tutorial

Answer 1

  Required: rx.Scheduler!

Required means the signature is Observable.observeOn(rx.Scheduler)

  Found: io.reactivex.Scheduler!

Found means the signature is io.reactivex.Scheduler AndroidSchedulers.mainThread()

This means that the Observable is a RxJava 1 observable, while the RxAndroid version used is built for RxJava 2. Since you mentioned that the observable is provided by a library it means that library is built using RxJava 1.

You have 3 options to fix this:

1. Figure out if the library in question has an RxJava 2 version, or contribute those updates to the project yourself.
2. Use akarnokd/RxJava2Interop to convert the old Observable to RxJava 2. (RxJavaInterop.toV2Observable(Observable);)
3. Switch the other dependencies back to RxJava 1.

Sapiential

Thanks for the clear explanation! What's weird is that I upgraded library to RxJava2 and the problem still persists. – Tutorial

RxJava and RxJava 2 use completely different packages, so if RxJava 1 is still available simply adding RxJava 2 as a dependency will change nothing. – Sapiential

Yep I Know, I switched imports from 'rx.Observable' to 'io.reactivex.Observable' also. Still no success :( – Tutorial

In case anyone else is receiving this error while using Retrofit, this post is helpful in resolving retrofit RxJava1 to RxJava2 errors #43434573 – Emeliaemelin

Answer 2

1.add :

   //RX JAVA
    implementation "io.reactivex.rxjava3:rxjava:3.0.0-RC6"

    implementation "io.reactivex.rxjava2:rxandroid:2.0.2"

2.Write this code :

  val taskObservable: Observable<Task> = Observable.fromIterable(DataSource.createTaskList())
            .subscribeOn(Schedulers.io())
            .observeOn(AndroidSchedulers.mainThread())

    }

3.add these imports :

import io.reactivex.Observable
import io.reactivex.android.schedulers.AndroidSchedulers
import io.reactivex.disposables.Disposable
import io.reactivex.functions.Function
import io.reactivex.schedulers.Schedulers

NOTE :

if you are using KOTLIN, So it is better to use RX Kotlin! just add two lines in your build.gradle :

//rxkotlin
    implementation "io.reactivex.rxjava2:rxkotlin:2.4.0"
    implementation "io.reactivex.rxjava2:rxandroid:2.0.2"

Prostomium

Answer 3

please include this in your gradle import

rxandroid_version="2.0.1"

implementation "io.reactivex.rxjava2:rxandroid:$rxandroid_version"

add this to your project

import io.reactivex.android.schedulers.AndroidSchedulers

Roath

Answer 4

use

.subscribeOn(io.reactivex.rxjava3.schedulers.Schedulers.io())

Misbecome

just a suggestion: When answering old question with multiple solutions with upvotes, try to provide some more details to understand the answer in context to the original question. Also provide the link to the documentation if possible. – Zannini

Answer 5

Try to use these dependencies it works for me :

implementation 'io.reactivex.rxjava2:rxandroid:2.1.1'
implementation 'io.reactivex.rxjava2:rxjava:2.x.x'

Guitarist

Answer 6

Replace the following:

implementation 'io.reactivex.rxjava2:rxandroid:2.1.1'

With:

implementation "io.reactivex.rxjava3:rxandroid:3.0.0"

Kee