Question

我的应用程序具有文件下载选项，该选项使用alamofire下载方法下载文件。下载完成后，我需要提供文件预览，而不将其保存到内部/云存储中。我该如何实现类似whatsapp的功能，该功能可以在下载文件后显示预览。

* Deen's likes a Harry Potter Series book.

Answer 1

要显示文件的预览，请使用Apple的QuickLook框架，该框架可让您嵌入预览各种文件类型，包括iWork文档，Microsoft Office文档，PDF，图像等，而无需编写太多内容代码。

首先，导入QuickLook框架，然后使您的视图控制器符合QLPreviewControllerDataSource协议。

参考：

代码：

class ViewController: UIViewController {
    var previewItem = URL!

    func downloadFile(fileUrl: URL) {
        let destination = DownloadRequest.suggestedDownloadDestination(for: .documentDirectory)

        Alamofire.download(fileUrl, to: destination)
        .response(completionHandler: { (downloadResponse) in

            let previewController = QLPreviewController()
            previewController.dataSource = self
            self.previewItem = downloadResponse.destinationURL
            self.present(previewController, animated: true, completion: nil)
        })
    }
}

extension ViewController: QLPreviewControllerDataSource {
    func numberOfPreviewItems(in controller: QLPreviewController) -> Int {
        return 1
    }

    func previewController(_ controller: QLPreviewController, previewItemAt index: Int) -> QLPreviewItem {
       return self.previewItem as QLPreviewItem
    }
}

Answer 2

这是使用Alamofire的一种解决方案。有人可以帮忙。

步骤：

Alamofire具有出色的人员，可以直接下载并保存/写入您的文件放入光盘。
返回保存下载文件的路径。
使用UIDocumentInteractionController传递文件路径

然后显示此视图

 import Alamofire

     extension UIViewController : UIDocumentInteractionControllerDelegate{


     func downloadFileForPreview(fileName: String, fileExtension: String, filePath: String )  {


         let destination: DownloadRequest.DownloadFileDestination = { _, _ in
             let documentsURL = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask)[0]

             let fileWithExtension = "file.\(fileExtension)"

             let fileURL = documentsURL.appendingPathComponent(fileWithExtension)

             return (fileURL, [.removePreviousFile, .createIntermediateDirectories])
         }
         //UtilitySwift.showUniversalLoadingView(true)
         Alamofire.download(filePath, to: destination).response {  response in
             debugPrint(response)
         //UtilitySwift.showUniversalLoadingView(false)

             if response.error == nil, let storeFilePath = response.destinationURL?.path {
                 //let image = UIImage(contentsOfFile: imagePath)
                 self.previewDocument(withFilePath: response.destinationURL)
                 print(storeFilePath)

             }

             else{
                 UtilitySwift.showErrorMessage(message: response.error?.localizedDescription ?? "Error occured when downloading" )
                 print(response.error?.localizedDescription ?? "")
             }

         }
     }


     //  Converted to Swift 5.1 by Swiftify v5.1.29672 - https://objectivec2swift.com/
     func previewDocument(withFilePath filePath: URL?) {

         var documentInteractionController: UIDocumentInteractionController?

         if filePath != nil {
             // Initialize Document Interaction Controller
             if let filePath = filePath {
                 documentInteractionController = UIDocumentInteractionController(url: filePath)
             }

             // Configure Document Interaction Controller
             documentInteractionController?.delegate = self as UIDocumentInteractionControllerDelegate

             //if not possible to open
             if !documentInteractionController!.presentPreview(animated: true) {
                 documentInteractionController?.presentOptionsMenu(from: CGRect.zero, in: self.view, animated: true)
             }

         } else {
             // error
             print("file preview error")
         }
     }
     //UIDocumentInteractionControllerDelegate
     public func documentInteractionControllerViewControllerForPreview(_ controller: UIDocumentInteractionController) -> UIViewController {
         self
     }

     }

从任何UIViewController呼叫

self.downloadFileForPreview(fileName: "file", fileExtension: fileExt ?? "", filePath: REPLACE_WITH_DOWNLOAD_URL)

直接在应用程序中显示下载文件的预览

2 个答案: