From Xojo Documentation
| This class is supported on Mobile (iOS).
Use ＃If...＃Endif with the Target... constants to ensure you only use this class where it is supported.
An iOS screen that controls specific layouts depending on the type of device being used.
You cannot directly add controls to an iOSScreen. You add controls to iOSViews or iOSContainerControls.
An iOSScreen allows you to specify how your app looks depending on the type of device being used. For example, on an iPhone you can have your app display a single View that contains a Table with a list of items. To do this, you select the View for the Content property in the Inspector for the DefaultiPhoneScreen. The iPhoneScreen is set in the App Inspector as the default screen to use for an iPhone.
On an iPad, you may instead want to have a split screen with a list of items on the left and detail information on the right. You can do this by setting the Content property for DefaultiPadScreen to be Split and then setting the views for the Main and Detail sections. Refer to iOS Split Screen in the User Guide for more information.
You can have multiple iOSScreens in your project and switch them at run-time. To do so you use the iOSApplication.CurrentScreen property and change the content like this: