如何在IOS中访问下载的文件？

Question

我已经在 IOS 中下载了文件，并在下载它的应用程序的当前会话中成功地在播放器中打开。下载文件后，我的路径是：

 file:///var/mobile/Containers/Data/Application/2644B0D9-A68E-4A70-BAC3-2747949A980D/Documents/videoplayback.m4a 

但是当我关闭应用程序并尝试在下一个会话中使用相同的 URL 时，即当应用程序再次打开时，它就不起作用了。当我检查容器时，它显示文件仍然存在。

Answer 1

每个会话都是独一无二的，你必须像这样得到它

func url(for fileName: String, extension: String) -> URL? {
   guard let documentsURL = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first else { return nil }
   return documentsURL.appendingPathComponent(fileName).appendingPathExtension(extension)
}

let url = url(for: "videoplayback", extension: "m4a")

Answer 2

您可以使用最常用的方法，那就是使用UIDocumentInteractionController 和UIAlertController

检查这部分使用流行的Alamofire 和progressview 的代码。请注意，如果您在控制器中使用它，它必须实现以下委托 UIDocumentInteractionControllerDelegate

这里是完整的带有下载功能的源代码：

class MyController: UIViewController, UIDocumentInteractionControllerDelegate {

        var progressView: UIProgressView?    

        override func viewDidLoad() {
            super.viewDidLoad()
        }               

        func downloadCommentFile(id: Int) {
            let destination = DownloadRequest.suggestedDownloadDestination(for: .documentDirectory)  

            //MARK: Progress controller
            let alertView = UIAlertController(title: "Downloading", message: "Downloading file", preferredStyle: .alert)
            alertView.addAction(UIAlertAction(title: "Cancel", style: .cancel, handler: nil))

            //  Show UIAlertController it to your users
            present(alertView, animated: true, completion: {
                //  Add your progressbar after alert is shown (and measured)
                let margin:CGFloat = 8.0
                let rect = CGRect(x: margin, y: 72.0, width: alertView.view.frame.width - margin * 2.0 , height: 10.0)
                self.progressView = UIProgressView(frame: rect)
                self.progressView!.progress = 0
                self.progressView!.tintColor = self.view.tintColor
                alertView.view.addSubview(self.progressView!)
            })

            let url = "http://MyUrl/DownloadFile"
            let headers = ["Header1": "header 1 value"]

            Alamofire.download(url,
                method: .post,
                parameters: ["id": id],
                encoding: JSONEncoding.default,
                headers: headers,
                to: destination).downloadProgress(closure: { (progress) in
                    //progress closure                  
                    self.progressView?.setProgress(Float(progress.fractionCompleted), animated: true)
                }).response(completionHandler: { (DefaultDownloadResponse) in
                    //here you able to access the DefaultDownloadResponse
                    //result closure
                    alertView.dismiss(animated: true, completion: {
                        let viewer = UIDocumentInteractionController(url: DefaultDownloadResponse.destinationURL!)
                        viewer.delegate = self
                        viewer.presentPreview(animated: true)
                })
            })      
        }

        func documentInteractionControllerViewControllerForPreview(_ controller: UIDocumentInteractionController) -> UIViewController {
            return self
        }

        private func documentInteractionControllerViewForPreview(controller: UIDocumentInteractionController!) -> UIView! {
            return self.view
        }

        func documentInteractionControllerRectForPreview(_ controller: UIDocumentInteractionController) -> CGRect {
            return self.view.frame
        }
    }