In onCreate(), we follow the standard recipe for defining our fragment if (and only if) we were started new, rather than restarted after a configuration change, by seeing if the fragment already exists. If we do need to add the fragment, we retrieve a string extra from the Intent used to launch us (identified as EXTRA_FILE), create an instance of SimpleContentFragment using that value from the extra, and execute a FragmentTransaction to add the SimpleContentFragment to the UI.