My app offers the user the opportunity to put an event in his native calendar.

For that, I refer to an online webcal:// URL.

Since the underlying .ics file is quite big (containing quite a few events), it sometimes (also depending on the network performance)takes a while before the "Do you want to subscribe"-dialog sequence kicks in.

I would like to give the user some feedback in the mean time, like a spinner, or a changing graphic, for him to know that something is going to happen.

Question: how does my app know, that the "Do you want to subscribe"-dialog has been shown, and that the user has chosen either a Cancel of OK button in that dialog, so I can stop the spinner?