Implications of porting an app from iOS to Android

Hi,

I'm currently in the process of converting my app from Titanium to Xamarin. Things are going great!

But I'm having one concern though:

Xamarin says that you can easily build an app for iOS, Android & Windows but when you come to think about it: the whole interface code has to be rewritten since different OSes use different interface elements.

Then, most app nowadays use REST APIs as a backend. What's left to /universal-ize/?

I'm thinking about what code will be really re-usable?

For example, I have an UITableView in one of my view and a UITableViewSource implementation to feed it. What would I need to do to make that working on Android for example?

I'm still juggling between going 100% native or with Xamarin and I need to take a decision today about it. So feel free to try to convince me!

Thanks and have a nice day