Provide a way for the SpaceOnClickListener to veto switching to the clicked item

Under certain circumstances I want to do something when one of the items is clicked, but prevent that item from being selected as the current item. Could be implemented as the onItemClick method instead of being void returning a boolean, indicating whether it wants to allow the view to switch to the clicked item or not.

I tried to work around that by setting the currently selected item back to the previous one from the click listener itself, but that doesn't work as the actual switch to the clicked item only occurs after the listener has been called.

Start by locating SpaceOnClickListener and the code that switches to the clicked item after the listener runs. Trace the click flow and define the listener result needed to allow or veto selection; done means a clicked item can trigger the callback without becoming current when vetoed.

Written by the indexing model from the issue text.