Use an IPartListener
to listen to part activation events.
Set the listener up in your view initialization:
getSite().getPage().addPartListener(partListener);
(and don't forget to remove the listener in the view dispose).
Among other things this will give you part activation events:
public void partActivated(IWorkbenchPart part)
If part
is an instance of IEditorPart
then it is an editor being activated. So you just need to keep track of this activated editor.