最佳实践实施改造回调来重新创建活动？

我切换到改造，并试图了解正确的架构，使用它异步回调。

I'm switching to Retrofit and trying to understand proper architecture for using it with async callbacks.

例如我有一个接口：

interface RESTService{
    @GET("/api/getusername")
    void getUserName(@Query("user_id") String userId, 
                     Callback<Response> callback);
}

和我跑这从主要活动：

RestAdapter restAdapter = new RestAdapter.Builder()
        .setServer("WEBSITE_URL")     
        .build();
RESTService api = restAdapter.create(RESTService.class);
api.getUserName(userId, new Callback<Response> {...});

然后用户旋转设备，我还新创建活动...什么是发生在这里？我怎样才能得到响应新的活动（我假设的背景下，API调用会比第一个活动的生命执行长）。也许我必须使用回调还是什么的静态实例？请告诉我正确的方式......

Then user rotates the device and I have newly created activity... What was happen here? How can I get response to the new activity (I assume that api call in background will execute longer than first activity life). Maybe I must use static instance of callback or what? Please show me the right way...