UIDocumentMenuViewController第一次加载时间稍长

Question

let documentMenuController = UIDocumentMenuViewController(documentTypes: ["public.data"], in: .import)
        documentMenuController.delegate = self
        documentMenuController.modalPresentationStyle = .formSheet
        documentMenuController.addOption(withTitle: "first Item", image: UIImage.init(named: "hey"), order: .first, handler: { _ in
        })
        present(documentMenuController, animated: true, completion: nil)

我正在使用此代码来显示文档菜单有什么方法可以显示进度条，直到它加载。