使用NSURLSessionDownloadTask进行断点下载

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////  NSURLSessionDownloadViewController.swift//  NSURLSessionDemo////  Created by Benjamin on 11/21/15.//  Copyright  2015 Benjamin. All rights reserved.//

import UIKit

class NSURLSessionDownloadViewController: UIViewController,NSURLSessionDownloadDelegate {    @IBOutlet weak var progressBar: UIProgressView!    @IBOutlet weak var image: UIImageView!    let imageStringURL = "http://carolinehjq.com/images/avatar.jpg"    var task: NSURLSessionDownloadTask? = nil    var partialData: NSData? = nil    let fileManager = NSFileManager.defaultManager()    var session: NSURLSession!    var request: NSURLRequest!

override func viewDidLoad() {        super.viewDidLoad()        self.session = getSession()        self.request = getRequest(imageStringURL)        self.progressBar.progress = 0    }

required init?(coder aDecoder: NSCoder) {        super.init(coder: aDecoder)    }

//取得单个session    func getSession() -> NSURLSession {        let session = NSURLSession(configuration: NSURLSessionConfiguration.defaultSessionConfiguration(), delegate: self, delegateQueue: nil)        return session    }

/**     return a request by url of image

- parameter imageStringURL: imageStringURL

- returns: NSURLRequest     */    func getRequest(imageStringURL: String) -> NSURLRequest {        let url = NSURL(string: imageStringURL)        return NSURLRequest(URL: url!)    }

// Start Action    @IBAction func start(sender: UIButton) {        self.task = self.session.downloadTaskWithRequest(self.request)        self.task?.resume()    }

// Pause Action    @IBAction func pause(sender: UIButton) {        print("pause download task")        if self.task != nil {            //取消下载任务，把下载好的数据存起来            self.task?.cancelByProducingResumeData({ (resumeData: NSData?) -> Void in                self.partialData = resumeData                self.task = nil            })        }    }

// Resume Action    @IBAction func resume(sender: UIButton) {        print("resume download task")        if self.task == nil {            if self.partialData != nil {                self.task = self.session.downloadTaskWithResumeData(self.partialData!)            } else {                self.task = self.session.downloadTaskWithRequest(self.request)            }        }        self.task?.resume()    }

/**     创建文件本地保存目录

- parameter location: download location url

- returns: NSURL     */    func createDirectoryForDownloadItemFromURL(location: NSURL!) -> NSURL{        let documentURL: NSURL = (fileManager.URLsForDirectory(.DocumentDirectory, inDomains: .UserDomainMask))[0]        return documentURL.URLByAppendingPathComponent(location.lastPathComponent!)    }

/**     把文件拷贝到指定路径

- parameter location:    original location     - parameter destination: destinate location

- returns: success is true, else false     */    func copyTempFileAtURL(fromLocation location: NSURL, toDestination destination: NSURL) -> Bool {        do {            try fileManager.copyItemAtURL(location, toURL: destination)        } catch {            print("file copy error")            return false        }        return true    }

//MARK:下载完成调用    func URLSession(session: NSURLSession, downloadTask: NSURLSessionDownloadTask, didFinishDownloadingToURL location: NSURL) {        //下载完成后，文件是放在一个临时目录，需要开发者自己拷到防止该文件的目录        let destination = createDirectoryForDownloadItemFromURL(location)        print("download success for url: \(destination)")        //如果文件copy成功        if copyTempFileAtURL(fromLocation: location, toDestination: destination) {            dispatch_async(dispatch_get_main_queue(), { () -> Void in                let image1 = UIImage(contentsOfFile: destination.path!)                self.image.image = image1                self.image.contentMode = .ScaleAspectFill                self.image.hidden = false            })        } else {            print("copy file error")        }        self.task = nil    }

//MARK:下载中调用    func URLSession(session: NSURLSession, downloadTask: NSURLSessionDownloadTask, didWriteData bytesWritten: Int64, totalBytesWritten: Int64, totalBytesExpectedToWrite: Int64) {        let currentProgress = Double(totalBytesWritten) / Double(totalBytesExpectedToWrite)        print("下载了\(currentProgress)")        dispatch_async(dispatch_get_main_queue()) { () -> Void in            self.progressBar.progress = Float(currentProgress)            self.progressBar.hidden = false        }    }

//MARK:继续下载调用    func URLSession(session: NSURLSession, downloadTask: NSURLSessionDownloadTask, didResumeAtOffset fileOffset: Int64, expectedTotalBytes: Int64) {        print("resume...")    }

}

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Alamofire.download(.GET, "https://httpbin.org/stream/100", destination: destination)         .progress { bytesRead, totalBytesRead, totalBytesExpectedToRead in             print(totalBytesRead)

// This closure is NOT called on the main queue for performance             // reasons. To update your ui, dispatch to the main queue.             dispatch_async(dispatch_get_main_queue()) {                 print("Total bytes read on main queue: \(totalBytesRead)")             }         }         .response { _, _, _, error in             if let error = error {                 print("Failed with error: \(error)")             } else {                 print("Downloaded file successfully")             }         }