iOS:下载 .TXT 文件给出奇怪的结果

Question

我正在尝试在一个网站上下载 5MB 大小的 .txt 文件

我试着直接下载文件，它给出了正确的大小

我尝试通过 Android DownloadManager.Request 下载，它也提供了正确的大小

Except，在 iOS 中，当我尝试通过 NSURLConnection 下载它时，没有 1 秒，它显示成功下载 5MB 大小但是，当我 checkin 网络时，它显示我只使用了 25kb？

附言。如果我更改为下载与 .zip 文件相同的域，它会正确下载

问题链接:http://www.bluewindsolution.com/speed_test/downloads/download_file.txt

工作链接: http://www.bluewindsolution.com/speed_test/downloads/download_file.zip

这是代码

@IBAction func buttonClick(sender: AnyObject) {
    let timestamp = NSString(format: "%.0f", NSDate().timeIntervalSince1970)
    let url:NSURL = NSURL(string: "http://www.bluewindsolution.com/speed_test/downloads/download_file.txt?time=\(timestamp)")!
    var request:NSURLRequest = NSURLRequest(URL: url, cachePolicy: NSURLRequestCachePolicy.ReloadIgnoringLocalCacheData, timeoutInterval: 30.0)
    startDate = NSDate()
    NSURLConnection(request: request, delegate: self)
}

func connectionDidFinishDownloading(connection: NSURLConnection, destinationURL: NSURL) {
    println("finishdownload \(destinationURL)")

    println("timetotal: \(timetotal)")
    println("speed: \(speed) mbps")
    println("filesize: \(filesize)") // it's show 5MB but network just receive only 25KBps ?  it's also not the cache because it's happen at the first time also.

    connection.cancel()
}

func connection(connection: NSURLConnection, didWriteData bytesWritten: Int64, totalBytesWritten: Int64, expectedTotalBytes: Int64) {
    let currentDate:NSDate = NSDate()

    let tt = currentDate.timeIntervalSinceDate(startDate)
    timetotal = tt // to get total time
    speed = Double(totalBytesWritten)/1024/1024*8/tt  // to get speed MBps
    filesize = Double(totalBytesWritten)/1024/1024  // to get as MB

    // use this to get result as real time
    //println("timetotal: \(totaltime)")
    //println("speed: \() mbps")
    //println("filesize: \()")
}

输出结果

模拟器网络接收结果

Answer 1

方法 connectionDidFinishDownloading 似乎有问题。请使用下面的委托(delegate)方法，它正在工作

  var mData = NSMutableData()
  func connection(connection: NSURLConnection, didReceiveData data: NSData) {
    mData.appendData(data)
    println("loading")
  }

  func connectionDidFinishLoading(connection: NSURLConnection) {
    let documentsPath = NSSearchPathForDirectoriesInDomains(.DocumentDirectory, .UserDomainMask, true)[0] as! NSString
    let filePath = documentsPath.stringByAppendingPathComponent("text.txt")
    mData.writeToFile(filePath, atomically: true)
    println("\(filePath)")
  }

  func connection(connection: NSURLConnection, didFailWithError error: NSError) {
    println("\(error)")
  }