swift - UIDocumentPickerViewController 从不调用 didPickDocument 方法

Question

我的文档选择器正确打开，我可以看到我的所有文件（谷歌驱动器），但是当我选择一个时，什么也没有发生。观点不以为然，仅此而已。我错过了什么吗？这在更新 Xcode 和 Swift 之前有效。

func selectDocument(_ sender: UIButton!){
    let documentPickerVC = UIDocumentPickerViewController(documentTypes: ["org.openxmlformats.wordprocessingml.document", "com.microsoft.word.doc"], in: UIDocumentPickerMode.import)
    documentPickerVC.delegate = self
    self.present(documentPickerVC, animated: true, completion: nil)
}

func documentPicker(_ documentPicker: UIDocumentPickerViewController, didPickDocumentAt url: URL) {
    print("file picked: \(url)")
    documentPicker.dismiss(animated: true, completion: nil)
}

也没有什么“失败”，它只是没有调用那个documentPicker方法。

我有一个类似的用于选择媒体的工具，并且效果很好...

func selectMedia(_ sender: UIButton!){
    if UIImagePickerController.isSourceTypeAvailable(UIImagePickerControllerSourceType.photoLibrary){
        picker.delegate = self
        picker.allowsEditing = false
        picker.mediaTypes = [kUTTypeMovie as String]
        self.present(picker, animated: true, completion: nil)
    }
}
func imagePickerController(_ picker: UIImagePickerController, didFinishPickingMediaWithInfo info:[String: Any]) {
    let url = info[UIImagePickerControllerMediaURL] as! URL
    print("media picked: \(url)")
}