Dec 22, 2014, 9:07:04 AM12/22/14
The skin has a default implementation for an edit event (the popup), if you would like to provide your own, you can set a callback in agenda's setEditAppointmentCallback() method. This is a "hook" (nothing JavaFX specific there) to insert your own logic to replace the default.
Since Agenda will be having more skins, triggering on a double click is not a good idea. Who knows how appointments will be rendered in the other skins? Rendering and handling of the mouse is internal to the control and agenda will never expose a "double click" event. You could inspect the nodes the control uses, and register directly to those, but chances are high your code will break. But, as described above, agenda has an "edit appointment" event, which now is bound to the menu in the top left corner of each appointment. I could also trigger this on double click. That seems intuitive.
TL;DR: get "double click" out of your head, there only are "add" and "edit" events.