使用FragmentActivity中的事件侦听器在android应用程序类中实现侦听器

Just started programming and I'm coding my first app. I've been wrecking my brain over this for long enough. I picked this up from tutorial where a listener is implemented in a ListFragment and the event listener is in a FragmentActivity that hosts the ListFragment. Here is how it is in the example (showing only the relevant part):Just started programming and I'm coding my firs