How to Pause and Resume Downloading Files with ASI

Question

I m using ASIHTTP Request sample source code for downloading urls. My question is that how to pause and resume the downloading files.

Please Help.

Answer 1

Deprecation Notice

ASIHTTP was deprecated around 2011, if you want network connectivity now, you should look up AFNetworking for ObjC or Alamofire for Swift, or stick to the native support:

For native support, in iOS 7 Apple added the NSURLSession, which can start download tasks (NSURLSessionDownloadTask), and these can be cancelled and restarted, check the method downloadTaskWithResumeData(_:) from NSURLSession, that has a very good explanation.

ASIHTTP is no longer needed, if you gotta are keeping a legacy app running, well, good luck.

Original Answer

Posted on 2011

ASI itself can resume a download from a file using [myASIRequest setAllowResumeForFileDownloads:YES];, check out the How-to-Use for an example.

Edit: Ok, there's no easy way to pause a download (a [myRequest pause] would be ideal). After reading and trying for a while, turns out that cancelling the request and resending it again is the only way.

For example, here's an example class I made:

@interface TestViewController : UIViewController <ASIHTTPRequestDelegate>
{
    ASIHTTPRequest *requestImage;
    UIImageView *imageViewDownload;
}

@property (nonatomic, retain) IBOutlet UIImageView *imageViewDownload;

- (IBAction)didPressPauseButton:(id)sender;
- (IBAction)didPressResumeButton:(id)sender;

To start (or restart) the download:

- (IBAction)didPressResumeButton:(id)sender
{
    if (requestImage)
        return;

    NSLog(@"Resumed");

    // Request
    requestImage = [ASIHTTPRequest requestWithURL:[NSURL URLWithString:@"http://www.myheadhealth.com/_IMAGES/cheese.jpg"]];

    // Using a temporary destination path just for show. 
    // Better pick a suitable path for your download.
    NSString *destinationDownloadPath = [NSTemporaryDirectory() stringByAppendingPathComponent:@"cheese.jpg"];
    NSString *temporaryDownloadPath = [NSTemporaryDirectory() stringByAppendingPathComponent:@"cheese.jpg-part"];

    requestImage.downloadDestinationPath = destinationDownloadPath;
    requestImage.temporaryFileDownloadPath = temporaryDownloadPath;
    requestImage.allowResumeForFileDownloads = YES;
    requestImage.delegate = self;
    [requestImage startAsynchronous];
}

In the exmaple above, I'm loading a random image of cheese I found, and storing a temporary download, and a full download.

Canceling the request will keep the contents of the temporary file intact, in fact, I made an UIImageView, and when pressing "Cancel" I could see a part of the downloaded file. If you want to try it out:

- (void)didPressPauseButton:(id)sender
{
    if (requestImage)
    {
        // An imageView I made to check out the contents of the temporary file.
        imageViewDownload.image = [UIImage imageWithContentsOfFile:requestImage.temporaryFileDownloadPath];

        [requestImage clearDelegatesAndCancel];
        requestImage = nil;

        NSLog(@"Canceled");
    }
}

- (void)requestFinished:(ASIHTTPRequest *)request
{
    imageViewDownload.image = [UIImage imageWithContentsOfFile:request.downloadDestinationPath];

    requestImage = nil;
}