Detecting Download in UIWebView

Question

I have a programatically crated UIWebView, and it is used to browse a iPhone-style site stored on my server. In this website, there are a few links to files users can download into my application. Right now, I'm trying to detect this with:

- (BOOL) webView:(UIWebView *) webView shouldStartLoadWithRequest:(NSURLRequest *) request navigationType:(UIWebViewNavigationType) navigationType
{
    url = [request URL];
    NSString *mimeType = [request valueForHTTPHeaderField:@"Content-Type"];
    NSLog(@"Content-type: %@", mimeType);
    if(mimeType == @"application/zip" || mimeType == @"application/x-zip" || mimeType == @"application/octet-stream")
    {
     NSLog(@"Downloading file!");
     [NSThread detachNewThreadSelector:@selector(download:) toTarget:self withObject:@"/tmp/file.ipa"];
     return NO;
    }
    return YES;
}

However, when this method is called, the content-type header is almost always (null), so I never am able to download a file.

How would you do this correctly?

Answer 1

You're trying to detect a Content-Type from an NSURLRequest which has not yet been made. You won't know the Content-Type until after the request is made using NSURLConnection. In this case, I'd probably just look at the file extension of the URL path.

Answer 2

So here's the problem: UIWebView doesn't download anything it can't display, and it doesn't know how to display a ZIP file. It will always fail before the Content-Type is filled in.

So, what to do? I don't know if your server-side app runs on more than the iPhone, but you could register a custom URL scheme with links like myapplication://example.com/stuff/yourhexurlgoeshere. You can create a custom URL handler for the myapplication scheme. A couple of seconds of Googling produced this site, which explains how to do it.

This has an additional benefit because if you, say, emailed such a link to another user, they could tap on it in Mail and have it open in your application.