title: How to notify a single listener on every failed Httprequest with Retrofit on Android
body: <p>I use <a href="http://square.github.io/retrofit/" rel="nofollow">Retrofit</a> to connect my app to a webbackend. We use the asynchronous callback methods to do requests at different points in the app. </p>
  
  <p>How would I add a listener that is notified every time a http-request fails. </p>
  
  <p>My current idea is to create a custom callback class that all callbacks in my app must extend. This callback will inform my listener on every failure. </p>
  
  <p>If I change all Interface to only except subtypes of this class and make the failure and success method final - with a callback to an abstract method - it should not be possible to miss a call in the whole application. </p>
  
  <p>Is there a simpler way then this? </p>