How to implement an async Callback using Square's Retrofit networking library

Question

As an iOS developer beginning to work with Android I came across Retrofit. I understand how to implement synchronous requests but am having trouble implementing asynchronous requests with success/failure callbacks. Specifically, the Callback syntax is unclear to me and there are no concrete examples of how to do this on the Retrofit website , the Square blogpost introducing Retrofit, or elsewhere that I've seen. Can someone please post some example code on this? I filed an issue in the Retrofit repo asking that they update the README with this info.

Answer 1

After some more research and just plain spending more time in the Android/Java world I figured this out, using the example from their docs.

Interface:

@GET("/user/{id}/photo")  
void listUsers(@Path("id") int id, Callback<Photo> cb);

Implementation:

RestAdapter restAdapter = new RestAdapter.Builder()
            .setServer("baseURL")     
            .build();
ClientInterface service = restAdapter.create(ClientInterface.class);

Callback callback = new Callback() {
    @Override
    public void success(Object o, Response response) {

    }

    @Override
    public void failure(RetrofitError retrofitError) {

    }
};
service.listUsers(666, callback);