设置UIWebView scrollView委托会导致错误

Question

So I have the following code:

 NSString *currSysVer = [[UIDevice currentDevice] systemVersion];
    if ([currSysVer compare:@"5.0" options:NSNumericSearch] != NSOrderedAscending) {
        webScrollView = self.webView_.scrollView;
    } else {
        webScrollView = [self.webView_ defaultScrollView];
    }

webScrollView.delegate = self

and when I scroll it gives me:

-[UIWebView scrollViewDidScroll:]: unrecognized selector sent to instance 0x8e8610

this doesn't make any sense why the UIWebView is calling the scrollViewDidScroll\\

Answer 1

If you look here , UIWebView conforms to UIScrollViewDelegate. In essence it uses the same delegation, as UIWebView is scrollable (you might say it's a subclass of UIScrollView, though it's not explicitly stated in the documentation, likely a UIScrollView is a piece of the WebView).

Answer 2

I have found the solution for all version

UIScrollView* sv = nil;
    for (UIView* v in  _webview.subviews) {
        if([v isKindOfClass:[UIScrollView class]]){
            sv = (UIScrollView*) v;
            sv.scrollEnabled = NO;
            sv.bounces = NO;

    }
}

Answer 3

The UIWebView HAS-A a scrollView of which it is the delegate, meaning the scrollViewDidScroll : method is implemented by the UIWebView , because you are using the reference the UIWebView provides to its scrollView , you are now saying that you will be handling this callbacks including scrollViewDidScroll :, and clearly you are not which is why when the delegate call happens it fails.

Why are you trying to assign as the delegate of the webview scrollview?, that behavior is already implemented. I am not sure it will play nice if you try to alter that behavior, but in either case if you want to be the delegate of the scrollView then you have to implement the UIScrollViewDelegate protocol and then implement the required methods.