Calling a method when UIWebView scrolls

问题:

I have a UIWebView that contains a lot of text content. I need to be able to get the location of the UIWebView every time it moves. I am using this code to get the point:

pageYOffset = [[webView stringByEvaluatingJavaScriptFromString:@"window.pageYOffset"] intValue];

now I just need to make it so that this variables value is updated everytime the UIWebView position moves, or there is any scrolling. Is it possible to call a method whenever the UIWebView scrolls?

回答1:

You should extend UIWebView, like below

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

and implement scrollViewDidScroll on your controller like:

- (void) scrollViewDidScroll:(UIScrollView *)scrollView{
    NSLog("webview scrolled");
}

and don't forget to set your controller to the delegate property of UIWebView.

回答2:

I believe that if your header lists your VC as a UIScrollViewDelegate, you can use the -(void)scrollViewDidScroll:(UIScrollView *)scrollView method to find out when it scrolls.

回答3:

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];
}

回答4:

if your requirement is to keep loading webview when user scrolls then you should paste your code into

- (void)webViewDidStartLoad:(UIWebView *)webView