xcode 如何将文件下载链接到进度视图
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How can I link a file download with a Progress View
提问by Mike Sylver
My button code below download a file from a URL, I need to link it with a Progress View to show the Downloading Progress.
我下面的按钮代码从 URL 下载文件，我需要将它与进度视图链接以显示下载进度。
@IBAction func btnStream(sender: UIButton) {
// First you need to create your audio url
if let audioUrl = NSURL(string: "http://website.com/file.mp3") {
// then lets create your document folder url
let documentsUrl = NSFileManager.defaultManager().URLsForDirectory(.DocumentDirectory, inDomains: .UserDomainMask).first as! NSURL
// lets create your destination file url
let destinationUrl = documentsUrl.URLByAppendingPathComponent(audioUrl.lastPathComponent!)
println(destinationUrl)
// to check if it exists before downloading it
if NSFileManager().fileExistsAtPath(destinationUrl.path!) {
println("The file already exists at path")
// if the file doesn't exist
} else {
// just download the data from your url
if let myAudioDataFromUrl = NSData(contentsOfURL: audioUrl){
// after downloading your data you need to save it to your destination url
if myAudioDataFromUrl.writeToURL(destinationUrl, atomically: true) {
println("file saved")
} else {
println("error saving file")
}
}
}
}
}
How can i link my downloading progress with a Progress View in Swift?
如何将我的下载进度与 Swift 中的进度视图相关联？
采纳答案by Dharmesh Kheni
Here is complete working example for you:
这是您的完整工作示例：
import UIKit
class ViewController: UIViewController, NSURLSessionDownloadDelegate {
@IBOutlet weak var progressBar: UIProgressView!
@IBOutlet weak var progressCount: UILabel!
var task : NSURLSessionTask!
var percentageWritten:Float = 0.0
var taskTotalBytesWritten = 0
var taskTotalBytesExpectedToWrite = 0
lazy var session : NSURLSession = {
let config = NSURLSessionConfiguration.ephemeralSessionConfiguration()
config.allowsCellularAccess = false
let session = NSURLSession(configuration: config, delegate: self, delegateQueue: NSOperationQueue.mainQueue())
return session
}()
override func viewDidLoad() {
progressBar.setProgress(0.0, animated: true) //set progressBar to 0 at start
}
@IBAction func doElaborateHTTP (sender:AnyObject!) {
progressCount.text = "0%"
if self.task != nil {
return
}
let s = "http://www.qdtricks.com/wp-content/uploads/2015/02/hd-wallpapers-1080p-for-mobile.png"
let url = NSURL(string:s)!
let req = NSMutableURLRequest(URL:url)
let task = self.session.downloadTaskWithRequest(req)
self.task = task
task.resume()
}
func URLSession(session: NSURLSession, downloadTask: NSURLSessionDownloadTask, didWriteData bytesWritten: Int64, totalBytesWritten writ: Int64, totalBytesExpectedToWrite exp: Int64) {
println("downloaded \(100*writ/exp)")
taskTotalBytesWritten = Int(writ)
taskTotalBytesExpectedToWrite = Int(exp)
percentageWritten = Float(taskTotalBytesWritten) / Float(taskTotalBytesExpectedToWrite)
progressBar.progress = percentageWritten
progressCount.text = String(format: "%.01f", percentageWritten*100) + "%"
}
func URLSession(session: NSURLSession, downloadTask: NSURLSessionDownloadTask, didResumeAtOffset fileOffset: Int64, expectedTotalBytes: Int64) {
// unused in this example
}
func URLSession(session: NSURLSession, task: NSURLSessionTask, didCompleteWithError error: NSError?) {
println("completed: error: \(error)")
}
// this is the only required NSURLSessionDownloadDelegate method
func URLSession(session: NSURLSession, downloadTask: NSURLSessionDownloadTask, didFinishDownloadingToURL location: NSURL) {
let documentsDirectoryURL = NSFileManager().URLsForDirectory(.DocumentDirectory, inDomains: .UserDomainMask).first as! NSURL
println("Finished downloading!")
println(documentsDirectoryURL)
var err:NSError?
// Here you can move your downloaded file
if NSFileManager().moveItemAtURL(location, toURL: documentsDirectoryURL.URLByAppendingPathComponent(downloadTask.response!.suggestedFilename!), error: &err) {
println("File saved")
} else {
if let err = err {
println("File not saved.\n\(err.description)")
}
}
}
}
You can use NSURLSessionDownloadDelegateto achieve this whose method will be called when user downloading data.
您可以使用它NSURLSessionDownloadDelegate来实现此目的，当用户下载数据时将调用其方法。
This will show you the process into progressCountlabel and the progressBarwill show process as count will increment. you can modify this as per your need.
这将向您显示进入progressCount标签的过程，并且progressBar将显示过程作为计数将增加。您可以根据需要修改它。
You can download this example from HERE.
你可以从这里下载这个例子。
回答by Pintouch
Check this tutorial. It's in Objective-C, but it will be easy to convert to Swift.
检查本教程。它在 Objective-C 中，但很容易转换为 Swift。
The principle is to implement some NSURLConnectionDataDelegatefunctions on your VC :
原理是NSURLConnectionDataDelegate在你的 VC 上实现一些功能：
- connection:didReceiveResponse-> You can retrieve the size of the file that will be downloaded and estimate the download percentage with it.
- connection:didReceiveData-> It's the refresh function, it will be called multiple times during the download. You can compare the size of your incomplete NSData object with the size of the file.
- connectionDidFinishLoading-> This method is called at the end of the download process.
- connection:didReceiveResponse-> 您可以检索将要下载的文件的大小并估计下载百分比。
- connection:didReceiveData-> 它是刷新函数，在下载过程中会被多次调用。您可以将不完整的 NSData 对象的大小与文件的大小进行比较。
- connectionDidFinishLoading-> 在下载过程结束时调用此方法。
Hope it helps, and don't hesitate to comment if you have some troubles converting Obj-C to Swift.
希望它有所帮助，如果您在将 Obj-C 转换为 Swift 时遇到一些麻烦，请不要犹豫，发表评论。
