去掉UIWebView上下滚动出边界时的黑色阴影

    for (UIView *viewin [_webViewsubviews]){
        if ([viewisKindOfClass:[UIScrollView class]]){
            for (UIView *shadowViewin view.subviews){
                // 上下滚动出边界时的黑色的图片 也就是拖拽后的上下阴影
                if ([shadowViewisKindOfClass:[UIImageView class]]){
                    shadowView.hidden =YES;
                }
            }
        }
    }