dataTaskWithURL下载数据时,有什么方法可以迅速取得进展?
dataTaskWithURL
NSURLSession.sharedSession().dataTaskWithURL(...)
下载数据时,我需要显示进度栏。
您可以使用此代码通过进度条及其委托功能来显示下载过程。
import UIKit class ViewController: UIViewController,NSURLSessionDelegate,NSURLSessionDataDelegate{ @IBOutlet weak var progress: UIProgressView! var buffer:NSMutableData = NSMutableData() var session:NSURLSession? var dataTask:NSURLSessionDataTask? let url = NSURL(string:"http://i.stack.imgur.com/b8zkg.png" )! var expectedContentLength = 0 override func viewDidLoad() { super.viewDidLoad() progress.progress = 0.0 let configuration = NSURLSessionConfiguration.defaultSessionConfiguration() let manqueue = NSOperationQueue.mainQueue() session = NSURLSession(configuration: configuration, delegate:self, delegateQueue: manqueue) dataTask = session?.dataTaskWithRequest(NSURLRequest(URL: url)) dataTask?.resume() // Do any additional setup after loading the view, typically from a nib. } func URLSession(session: NSURLSession, dataTask: NSURLSessionDataTask, didReceiveResponse response: NSURLResponse, completionHandler: (NSURLSessionResponseDisposition) -> Void) { //here you can get full lenth of your content expectedContentLength = Int(response.expectedContentLength) println(expectedContentLength) completionHandler(NSURLSessionResponseDisposition.Allow) } func URLSession(session: NSURLSession, dataTask: NSURLSessionDataTask, didReceiveData data: NSData) { buffer.appendData(data) let percentageDownloaded = Float(buffer.length) / Float(expectedContentLength) progress.progress = percentageDownloaded } func URLSession(session: NSURLSession, task: NSURLSessionTask, didCompleteWithError error: NSError?) { //use buffer here.Download is done progress.progress = 1.0 // download 100% complete } }