Creating a custom event listener on an Android app

Define a callback interface

        public interface NewsUpdateListener 
        {
            void onNewsUpdate(<News data to be passed>);
        }

Provide a registration facility on the background thread which gets the RSS feed

    class <Background processing class name> 
    {
    ....
        ArrayList<NewsUpdateListener> listeners = new ArrayList<NewsUpdateListener> ();
    .... 
        public void setOnNewsUpdateListener (NewsUpdateListener listener) 
        {
            // Store the listener object
            this.listeners.add(listener);
        }
    ....
    }

Fire the callback when news is available

....
for (listener : listeners) 
{
    listener.onNewsUpdate(<News data to be passed>);
}
....

Register listener somewhere during initialization

....
    <class <Background processing class object>.registerListener
(
    new OnNewsUpdateListener() {
        onNewsUpdate(<News Data>) {
            // process news data
            runOnUIThread(new Runnable() {
                public void run() {
                    // refresh list view
                }
            }
        }
}
....