如何通过从UIDocumentPickerViewController中选择的WCSessionFileTransfer将文件从iPhone发送到Apple Watch

Question

我正在尝试通过WCSessionFileTransfer发送从UIDocumentPickerViewController上的ios应用中选择的文件

func documentPicker(_ controller: UIDocumentPickerViewController, didPickDocumentAt url: URL) {
        if controller.documentPickerMode == .import {
            session.transferFile(url, metadata: [url.lastPathComponent : url.pathExtension])
        }
    }

给出[DocumentManager]错误，无法为选择的URL关联缩略图，并且监视界面控制器的didReceive文件功能永不触发