I'm new in Xamarin and iOS development. I have problem with creating layout like on picture below.

<http://cdn.vanillaforums.com/xamarin.vanillaforums.com/FileUpload/6f/7eb37b9abb0d8cdcef8d238d1a4b2f.png>

I would like to have two views with fixed size on top and the bottom and one flexible in the middle. I want middle view to be flexible because I want to have same layout on 3,5 and 4 inch screens. 

Can you please send me some clues how to achieve that?