Well, I'm afraid that you are mixing up quite a few things.
Even for B4A !
You speak about a code module with an activity ?
If you have an Activity you have an Activit module ? Not a code module !!!
iOS is NOT Android !!!
You don't have ativities in iOS.
You have Pages, all in the same module.
If you have a concrete small project, showing the problem, we could look at, post it.