From Xojo Documentation
| This class is supported on Mobile.
Use ＃If...＃Endif with the Target... constants to ensure you only use this class where it is supported.
New in 2020r2
Used to asynchronously display alerts.
MobileMessageBox is asynchronous, any code after the Show method is executed after the message box is displayed. Use the Pressed event handler to get the results of a button selection and to run code based on the selection.
iOS UI Guidelines
Apple provides user interface guidelines for the text and buttons in a MessageBox.