Service methods cannot return void. retrofit

Question

This is my method in Interface. I am calling this function but app crash with this exception:

Caused by: java.lang.IllegalArgumentException: Service m

Answer 1

There is difference in Asynchronous in Retrofit 1.9 and 2.0

/* Synchronous in Retrofit 1.9 */

public interface APIService {

@POST("/list")
Repo loadRepo();

}

/* Asynchronous in Retrofit 1.9 */

public interface APIService {

@POST("/list")
void loadRepo(Callback cb);

}

But on Retrofit 2.0, it is far more simple since you can declare with only just a single pattern

/* Retrofit 2.0 */

public interface APIService {

@POST("/list")
Call loadRepo();

}

// Synchronous Call in Retrofit 2.0

Call call = service.loadRepo();
Repo repo = call.execute();

// Asynchronous Call in Retrofit 2.0

Call call = service.loadRepo();
call.enqueue(new Callback() {
@Override
public void onResponse(Response response) {

   Log.d("CallBack", " response is " + response);
}

@Override
public void onFailure(Throwable t) {

  Log.d("CallBack", " Throwable is " +t);
}
});