If you extend the lending period of a book, you get a ProgressDialog. If you cancel this dialog, you don't get the action canceled but a very strange behaviour.
The data structure List<ContentValues> for DetailledItem.baende, DetailledItem.copies, AccountData.lent and AccountData.reservations is a very bad choice because it is not properly defined, what those ContentValues should contain. I believe specific objects (like List<Copy>) make more sense. It is to be evaluated whether they are less efficient.
The app provides a listener for URLs starting with http://opacapp.de/: but is currently only capable of handling them if the URLs is for the library the currently selected account is also for.