B4A designer doesn't work with XML layouts. It works with binary files (.bal).
I think that there was a library that loads XML layouts. It should be quite simple to create such a library, though this is not the preferred method for creating layouts in B4A.
Ok, I can't import XML Layout and, therefore, i need to create its from scratch in B4A format.
My application needs to have an activity with three areas: on the left a listview, while on the right i want to display some data with label e bottom a serie of buttons from where i start others activities.