When I add a layout element to the centralwidget, that element stays in the middle of the window and does not move when the window is resized. How can I make it "fill" the whole area (and resize its children properly)? All children widgets of my layout are expanding properly.
If you mean adding a layout via the designer, you have to first put the child widgets (at least one) on the centralwidget and then right-click, and choose a layout in the "Lay out" menu that pops up.
