Ok so I have a page with a button and a listview. So I've created a column, put my button and then my listview which is calling a query and is populated by this query content.
When I have a listview alone on a page, it is easy to center verticaly the empty widget: I just have to center it, and because the listview cover the whole page, it centers perfectly in the middle of the screen.
But when I have a page with more than the list view, the listview does not cover the whole page anymore. And now center only center horizontaly, and I can't find a way to center verticaly.