如果用户在 swift iOS 中点击两次，则取消 NSURLSession

Question

我正在使用 NSURLSession，根据此线程，这是首选。

let url = NSURL(string: "http://www.whosebug.com")

let task = NSURLSession.sharedSession().dataTaskWithURL(url!) {(data, response, error) in
    println(NSString(data: data, encoding: NSUTF8StringEncoding))
}

task.resume()

我唯一的问题是当用户点击两次并且我想取消第一个请求时。我试过 task.cancel() 但打印语句仍然执行（即在 .cancel() 之后出现 NSDomainError）。我如何安全地取消此请求 (NSURLSessionDataTask)，而不触发 print 语句，或者甚至可能？

编辑：只是为了清楚。 URL 可能相同，我想取消第一个请求。

Answer 1

我就是这样解决问题的。当执行 task.cancel() 时，打印语句将不会被执行。检查字符串似乎有点老套，所以如果有人有更好的解决方案，我会接受那个。

let url = NSURL(string: "http://www.whosebug.com")

let task = NSURLSession.sharedSession().dataTaskWithURL(url!) {(data, response, error) in
    if (error?.userInfo?["NSLocalizedDescription"] as? String) == "cancelled"
            {
                return
            }
    println(NSString(data: data, encoding: NSUTF8StringEncoding))
}

task.resume()

Answer 2

我希望这是你可以使用的东西：

class ViewController: UIViewController , NSURLSessionDownloadDelegate {

    var download : NSURLSessionDownloadTask?
    var backgroundSession : NSURLSession?

    override func viewDidLoad() {
        super.viewDidLoad()

        let sessionConfiguration : NSURLSessionConfiguration = NSURLSessionConfiguration.backgroundSessionConfigurationWithIdentifier("CustomBackgroundIdentifier")
        backgroundSession = NSURLSession(configuration: sessionConfiguration, delegate: self, delegateQueue: NSOperationQueue.mainQueue())

        var btn = UIButton(frame: CGRectMake(0, 0, 100, 100))
        btn.backgroundColor = UIColor.redColor()
        btn.addTarget(self, action: "startDownload", forControlEvents: UIControlEvents.TouchDown)
        self.view.addSubview(btn)

        var btn2 = UIButton(frame: CGRectMake(0, 120, 100, 100))
        btn2.backgroundColor = UIColor.blueColor()
        btn2.addTarget(self, action: "cancelDownload", forControlEvents: UIControlEvents.TouchDown)
        self.view.addSubview(btn2)

    }

    func startDownload() {
        if download == nil {
            if let url = NSURL(string: "http://www.whosebug.com") {
                download = backgroundSession?.downloadTaskWithURL(url)
                download?.resume()
            }
        } else {
            resumeDownload()
        }
    }

    func pauseDownload() {
        if download != nil {
            download?.suspend()
        }
    }

    func resumeDownload() {
        if download != nil {
            download?.resume()
        }
    }

    func cancelDownload() {
        if download != nil {
            download?.cancel()
        }
    }

    func URLSession(session: NSURLSession, downloadTask: NSURLSessionDownloadTask, didFinishDownloadingToURL location: NSURL) {
        println("Session %@ download task %@ finished downloading to URL %@\n",
        session, downloadTask, location)
    }

    func URLSession(session: NSURLSession, downloadTask: NSURLSessionDownloadTask, didWriteData bytesWritten: Int64, totalBytesWritten: Int64, totalBytesExpectedToWrite: Int64) {
        println("downloaded: %i",totalBytesWritten)
    }
}

如果用户在 swift iOS 中点击两次，则取消 NSURLSession

Cancel NSURLSession if user taps twice in swift iOS

ios

nsurlsession

swift