NavigationController自带toolbar不显示内容不生效

var items = [deleteBtn,flexibleSpaceBarButtonItem,cameraButtonItem]
self.navigationController?.toolbar.items = items

 这样的方式是不生效的，下面的才行，真实坑苦了32岁的程序员新人啊

var items = [deleteBtn,flexibleSpaceBarButtonItem,cameraButtonItem]
self.setToolbarItems(items, animated: true)