Catch http response in Retrofit before passing it to the calling activity

Question

Right now we are using retrofit like this:

service.executeSomeRequest(UserPreferenceRequest userPreferenceRequest, new Callback         


        

Answer 1

Your custom callback can process the response in the base class first and then delegate to an abstract method.

public interface StatusResponse {
  Status getStatus();
}

public abstract class CustomCallback<T extends StatusResponse> implements Callback<T> {
  @Override public final void success(T data, Response response) {
    if (data.getStatus() == Status.OK) {
      success(data);
    } else {
      // Handle error..
    }
  }

  public abstract void success(T data);
}

Answer 2

You can combine the retrofit requests with an event bus and have a clean and centralised point for handling your responses.

All you need to do is define a Composed object like this:

public class GetUsers {
// Retrofit Request
public static final class Request {}

// Retrofit Callback
public static final class Callback 
      implements retrofit.Callback<Response response> {

    @Override
    public void success(Response response, 
         Response retrofitResponse) {
         // .... handle the code
         BusManager.post(new Event());
    }

    @Override
    public void failure(RetrofitError error) {}
         BusManager.post(new RetrofitErrorEvent(error));
    }

// Otto Event
public static final class Event {}

This object defines the Request, Callback and Event and this object is feed to the retrofit request.

 public void getUsers(){
     request.users(new GetUsers.Request(), new GetUsers.Callback());
 }

After this, in your main class looks like this:

public void onResume(){    
   controller.getUsers();
}

@Subscribe
public void onGetPostsEvent(GetPosts.Event event){
    textView.setText(event.getText());
}

For a more detailed explanation check this blog post: Otto + Retrofit – An elegant solution for Web Requests and you can find a working example here