How can I get a UIWebView's UIScrollView delegate methods called from within a standard UIViewController?

Question

So I just have a standard UIViewController with a UIWebView in it that displays a pdf. For the app functionality, I have need to be able to respond to the UIWebView's nested UIScrollView events like scrollViewWillBeginDragging, scrollViewDidScroll, etc.

The only way I can get access to the scrollView is to (it seems like a hack) go in and get it by the subviews array:

for (id subview in webView.subviews){
    if ([[subview class] isSubclassOfClass: [UIScrollView class]])  {
        UIScrollView * s = (UIScrollView*)subview;
        s.delegate = self;
        s.tag = 1;
        scrollView = s;
    }
}

But that seems to introduce more problems than it's worth, because I lose native UIScrollView stuff like zooming.

So to sum up what I'm needing:

What is the best way to set my UIViewController class as the delegate of the UIScrollView inside of the UIWebView? Is there something I need to do with subclassing my own UIWebView so that it handles events from it's built in UIWebView a certain way and then pass it along somehow to the UIViewController? How does that passing thing work anyway?

Please advise!

Thank you!

Answer 1

1. Have you checked there is only one UIScrollView subclass in the subviews? Bung in a log in your loop to see. If there is more than one, then you'll only pick up the last one using your code.

2. If there is just one UIScrollView subclass, you could try saving a reference to its delegate and then in your own delegate methods passing messages on after you have done your business.

So, in your loop, something like

originalDelegate = s.delegate

And then for the delegate methods, something like:

- (void) scrollViewDidScroll: (UIScrollView*) scrollView;
{
     // do your stuff

     [originalDelegate scrollViewDidScroll: scrollView];
}

You might need to check whether originalDelegate responds to the selector before calling it, i.e. if ([originalDelegate respondsToSelector: @selector(scrollViewDidScroll:)) etc. If it were me, I'd start by implementing all twelve delegate methods defined in the UIScrollView delegate protocol.

Not tested this, so will be interested to know if it can be made to work. Do note, the docs explicitly say that UIWebView "should not be subclassed"