在UITableViewController（Swift）上添加按钮

I am trying to add a button ontop of a uitableview controller table view. The view controller has a navigation controller and static cells, which is why it is a uitableviewcontroller and not a uiviewcontroller. Now I am trying to add a button at the bottom of the screen that is attached to the navigation controller so that it doesn't scroll with the table view.I am trying to add a button ontop of a uitablev