If this is the case, then:
- to run your program as it is now, in portrait mode, you would load your layout to a single 1080 wide x 1920 tall XUI panel, with the panel rotation set to 0 degrees.
- to run your program in landscape mode, you would load your layout to a single 1920 wide x 1080 tall XUI panel (should be able to reuse/resize the same panel as used for portrait mode), with the panel rotation set to 90 degrees (or -90 degrees or 270 degrees, depending on which way the user is looking at it).
I have done this in B4A but not B4J, but I'm pretty confident it will do the trick.