If you look at the first post in the related thread -> [B4X] [XUI] AS MsgBox/Dialog, near the bottom there is a "Notes" section that tells you which libraries you need.
OK. Found it. Tnx. But I still can't get it to run. Have 'B4X collections', 'Core', 'Reflections' & 'XUI' libraries loaded & still get syntax errors as indicated in 'errors.png' below.
Also - if you haven't done so already, you might want to look at some of the documentation here -> https://www.b4x.com/b4a.html#documentation - especially the Beginner's Guide.
The example I was referring to was contained in the file 'ASMsgBox Android Example.zip'. And I've read some of the documentation - thus have added the class as required, but still have an error - see prior post.
OK, thanks all. Finally got it load & run after studying the ASMsgBox.bas file. The problem was missing parameters in the 'InitializeWithoutDesigner' line.