Why does a UIWebView instance not call scrollViewDidScroll?

问题

iOS documention says, that the UIWebView class conforms to UIScrollViewDelegate. But an UIWebView instance does not call the scrollViewDidScroll method of its controller. The delegate is set just right by

[webView setDelegate:self];

and webViewDidFinishLoad is called successfully. The controller implements both delegates, UIWebViewDelegate and UIScrollViewDelegate, like this:

@interface WebviewController : UIViewController<UIWebViewDelegate, UIScrollViewDelegate>{
    UIWebView *webView;
}

Browsing SO leads to that category solution:

@implementation UIWebView(CustomScroll)
- (void) scrollViewDidScroll:(UIScrollView *)scrollView{
    [self.delegate scrollViewDidScroll: scrollView];
}
@end

That category approach does basically the same: Calling the delegate's scrollViewDidScroll method. So why does the the first approach not work?

回答1:

My guess is you set up delegate only for UIWebView. Try setting delegate of scrollView.

webView.scrollView.delegate = self

it should be ok.

回答2:

This is not correct. If you will use:

@implementation UIWebView(CustomScroll)
- (void) scrollViewDidScroll:(UIScrollView *)scrollView{
    [self.delegate scrollViewDidScroll: scrollView];
}
@end

You will lose focus when try to enter data on page on iOS7 and more

You need to implement custom class for UIWevView and overwrite scrollViewDidScroll:

- (void) scrollViewDidScroll:(UIScrollView *)scrollView{
[super scrollViewDidScroll:scrollView];
[((id<UIScrollViewDelegate>)self.delegate) scrollViewDidScroll:scrollView];}

来源：https://stackoverflow.com/questions/12093826/why-does-a-uiwebview-instance-not-call-scrollviewdidscroll

标签

iphone

ios

uiwebview