Swift-如何打开存储在UserDefaults中的pdf文件？

我一直在尝试使用Swift在我的应用程序上打开一个文件。这是一个PDF文件，我通过URL从互联网上下载。下载部分对我来说很好，但我无法找到一种方法，通过我的应用程序上的本地位置打开相同的PDF文件，而不必再次下载。我知道我可以在下载后立即在网络视图中打开它，但我正计划这样做，这样文件就可以在没有互联网的情况下访问；因此，我将文件位置存储在UserDefaults中

我在网上到处阅读，也在youtube上搜索视频，但似乎找不到任何方法来实现这一点。另外，如果我不应该使用UserDefaults，或者因为我不想访问任何服务器而这样做似乎是最好的方式，请纠正我

到目前为止，我使用的代码如下：

import UIKit
import WebKit

class ViewController: UIViewController, URLSessionDownloadDelegate, UIDocumentInteractionControllerDelegate {

var downloadTask: URLSessionDownloadTask!
var backgroundSession: URLSession!
let name = "Accounting"

@IBAction func startDownload(_ sender: AnyObject) {
    let url = URL(string: "https://pastpapers.papacambridge.com/Cambridge%20International%20Examinations%20(CIE)/AS%20and%20A%20Level/Accounting%20(9706)/2005%20Nov/9706_w05_qp_4.pdf")!
    downloadTask = backgroundSession.downloadTask(with: url)
    downloadTask.resume()
}
@IBAction func pause(_ sender: AnyObject) {
    if downloadTask != nil{
        downloadTask.suspend()
    }
}
@IBAction func resume(_ sender: AnyObject) {
    if downloadTask != nil{
        downloadTask.resume()
    }
}
@IBAction func cancel(_ sender: AnyObject) {
    if downloadTask != nil{
        downloadTask.cancel()
    }
}
@IBOutlet var progressView: UIProgressView!
@IBOutlet weak var webView: WKWebView!

override func viewDidLoad() {
    super.viewDidLoad()
    let backgroundSessionConfiguration = URLSessionConfiguration.background(withIdentifier: "backgroundSession")
    backgroundSession = Foundation.URLSession(configuration: backgroundSessionConfiguration, delegate: self, delegateQueue: OperationQueue.main)
    progressView.setProgress(0.0, animated: false)
}

override func viewWillAppear(_ animated: Bool) {
    if let file = UserDefaults.standard.object(forKey: "Biology") {
        print(file)       //prints the file location where UserDefaults stores it in
    }
}
override func didReceiveMemoryWarning() {
    super.didReceiveMemoryWarning()
    // Dispose of any resources that can be recreated.
}


func showFileWithPath(path: String){
    let isFileFound:Bool? = FileManager.default.fileExists(atPath: path)
    if isFileFound == true{
        UserDefaults.standard.set(path, forKey: "Biology")

        let viewer = UIDocumentInteractionController(url: URL(fileURLWithPath: path))
        viewer.delegate = self
        viewer.presentPreview(animated: true)
    }
}

//URLSessionDownloadDelegate
func urlSession(_ session: URLSession,
                downloadTask: URLSessionDownloadTask,
                didFinishDownloadingTo location: URL){

    let path = NSSearchPathForDirectoriesInDomains(FileManager.SearchPathDirectory.documentDirectory, FileManager.SearchPathDomainMask.userDomainMask, true)
    let documentDirectoryPath:String = path[0]
    let fileManager = FileManager()
    let destinationURLForFile = URL(fileURLWithPath: documentDirectoryPath.appendingFormat("/\(name).pdf"))

    if fileManager.fileExists(atPath: destinationURLForFile.path){
        showFileWithPath(path: destinationURLForFile.path)
    }
    else{
        do {
            try fileManager.moveItem(at: location, to: destinationURLForFile)
            // show file
            showFileWithPath(path: destinationURLForFile.path)
        }catch{
            print("An error occurred while moving file to destination url")
        }
    }
}
func urlSession(_ session: URLSession,
                downloadTask: URLSessionDownloadTask,
                didWriteData bytesWritten: Int64,
                totalBytesWritten: Int64,
                totalBytesExpectedToWrite: Int64){
    progressView.setProgress(Float(totalBytesWritten)/Float(totalBytesExpectedToWrite), animated: true)
}

//URLSessionTaskDelegate
func urlSession(_ session: URLSession,
                task: URLSessionTask,
                didCompleteWithError error: Error?){
    downloadTask = nil
    progressView.setProgress(0.0, animated: true)
    if (error != nil) {
        print(error!.localizedDescription)
    }else{
        print("The task finished transferring data successfully")
    }
}

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

---

}

您需要发布相关代码。演示如何下载和存储文件。显示如何在UserDefaults中存储位置。显示稍后如何尝试从本地位置打开文件。显示变量的相关值。解释你对代码的实际问题。嗨@rmaddy，对不起，我现在更新了代码，包含了我使用的所有代码。也许这现在会有帮助。@Danny您在哪里显示文件？（找不到行。）我在

WKWebView

上遇到问题，并使用了

PDFView

，但如果您不显示它，这也没用。