Observe Progress of Data Download in Swift

Observe progress of Data download in Swift?

Don't use Data(contentsOf: url) to make synchronous request for urls that are not local resources. You should use URLSession.To observe the progress you need to set urlsessiondownloaddelegate https://developer.apple.com/documentation/foundation/urlsessiondownloaddelegate and to monitor the progress, use the method

func urlSession(_ session: URLSession, downloadTask: URLSessionDownloadTask, didWriteData bytesWritten: Int64, totalBytesWritten: Int64, totalBytesExpectedToWrite: Int64)

https://developer.apple.com/documentation/foundation/urlsessiondownloaddelegate/1409408-urlsession

Find the Download Progress of a file in swift

The progress status can be calculated in

URLSession(_:downloadTask:didWriteData:totalBytesWritten:totalBytesExpectedToWrite:)

This is a one of three required methods of protocol NSURLSessionDownloadDelegate. In my case the code of the method looks like this:

func URLSession(session: NSURLSession, downloadTask: NSURLSessionDownloadTask, didWriteData bytesWritten: Int64, totalBytesWritten: Int64, totalBytesExpectedToWrite: Int64) {
    // println("download task did write data")

    let progress = Float(totalBytesWritten) / Float(totalBytesExpectedToWrite)

    dispatch_async(dispatch_get_main_queue()) {
        self.progressDownloadIndicator.progress = progress
    }
}

I've created a small project, which implements three different approaches:

• download synchronously
• download asynchronously
• download with progress

Check it out: http://goo.gl/veRkA7

get progress from dataTaskWithURL in swift

you can use this code for showing download process with progress bar with its delegate functions.

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
    }
}

How to link Firebase download file with a progress view?

Several thoughts:

• Don't download in memory and then write to disk--we have a method that downloads straight to the file system
• Attach listeners rather than a single completion handler--that way you can listen to progress updates
• Use something like MBProgressHUD to show an incremental progress bar
• No need to set the isNetworkActivityIndicatorVisible as we'll do that for you

Putting that together, you get something like:

// Create a reference to the file we want to download
let starsRef = storageRef.child("images/stars.jpg")

// Start the download (in this case writing to a file)
let downloadTask = storageRef.write(toFile: localURL)

// Start progress indicator

// Observe changes in status
downloadTask.observe(.progress) { snapshot in
  // Download reported progress
  let percentComplete = 100.0 * Double(snapshot.progress!.completedUnitCount)
    / Double(snapshot.progress!.totalUnitCount)
  // Update the progress indicator
}

downloadTask.observe(.success) { snapshot in
  // Download completed successfully
  // Stop progress indicator
}

// Errors only occur in the "Failure" case
downloadTask.observe(.failure) { snapshot in
  // An error occurred!
  // Stop progress indicator
}

Showing the file download progress with NSURLSessionDataTask

You need to implement following delegates:

<NSURLSessionDataDelegate, NSURLSessionDelegate, NSURLSessionTaskDelegate>

Also need to create two properties:

@property (nonatomic, retain) NSMutableData *dataToDownload;
@property (nonatomic) float downloadSize;

- (void)viewDidLoad {
    [super viewDidLoad];

    NSURLSessionConfiguration *defaultConfigObject = [NSURLSessionConfiguration defaultSessionConfiguration];

    NSURLSession *defaultSession = [NSURLSession sessionWithConfiguration: defaultConfigObject delegate: self delegateQueue: [NSOperationQueue mainQueue]];

    NSURL *url = [NSURL URLWithString: @"your url"];
    NSURLSessionDataTask *dataTask = [defaultSession dataTaskWithURL: url];

    [dataTask resume];
}

- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

- (void)URLSession:(NSURLSession *)session dataTask:(NSURLSessionDataTask *)dataTask didReceiveResponse:(NSURLResponse *)response completionHandler:(void (^)(NSURLSessionResponseDisposition disposition))completionHandler {
    completionHandler(NSURLSessionResponseAllow);

    progressBar.progress=0.0f;
    _downloadSize=[response expectedContentLength];
    _dataToDownload=[[NSMutableData alloc]init];
}

- (void)URLSession:(NSURLSession *)session dataTask:(NSURLSessionDataTask *)dataTask didReceiveData:(NSData *)data {
    [_dataToDownload appendData:data];
    progressBar.progress=[ _dataToDownload length ]/_downloadSize;
}

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