Unable to create call adapter for class example.Simple

In case of Kotlin and coroutines this situation happened when I forgot to mark api service function as suspend when I call this function from CoroutineScope(Dispatchers.IO).launch{}:

Usage:

    val apiService = RetrofitFactory.makeRetrofitService()    CoroutineScope(Dispatchers.IO).launch {        val response = apiService.myGetRequest()        // process response...    }

ApiService.kt

interface ApiService {       @GET("/my-get-request")       suspend fun myGetRequest(): Response<String>}

Short answer: return Call<Simple> in your service interface.

It looks like Retrofit 2.0 is trying to find a way of creating the proxy object for your service interface. It expects you to write this:

public interface SimpleService {    @GET("/simple/{id}")    Call<Simple> getSimple(@Path("id") String id);}

However, it still wants to play nice and be flexible when you don't want to return a Call. To support this, it has the concept of a CallAdapter, which is supposed to know how to adapt a Call<Simple> into a Simple.

The use of RxJavaCallAdapterFactory is only useful if you are trying to return rx.Observable<Simple>.

The simplest solution is to return a Call as Retrofit expects. You could also write a CallAdapter.Factory if you really need it.

add dependencies:

compile 'com.squareup.retrofit:retrofit:2.0.0-beta1'compile 'com.squareup.retrofit:adapter-rxjava:2.0.0-beta1'compile 'com.squareup.retrofit:converter-gson:2.0.0-beta1'

create your adapter this way:

Retrofit rest = new Retrofit.Builder()    .baseUrl(endpoint)    .addCallAdapterFactory(RxJavaCallAdapterFactory.create())    .addConverterFactory(SimpleXmlConverterFactory.create())    .build();

addCallAdapterFactory () and addConverterFactory () both need to be called.

Service:

public interface SimpleService {    @GET("/simple/{id}")    Call<Simple> getSimple(@Path("id") String id);}

Modify Simple to Call<Simple>.