IOS 去掉UITableViewHeaderView黏性

- (void)scrollViewDidScroll:(UIScrollView *)scrollView {  

    if (scrollView == _tableView) {  

        CGFloat sectionHeaderHeight = 36;

        if (scrollView.contentOffset.y <= sectionHeaderHeight && scrollView.contentOffset.y >= 0) {  

            scrollView.contentInset = UIEdgeInsetsMake(-scrollView.contentOffset.y, 0, 0, 0);  

        } else if (scrollView.contentOffset.y >= sectionHeaderHeight) {  

            scrollView.contentInset = UIEdgeInsetsMake(-sectionHeaderHeight, 0, 0, 0);  

        }  

    }  

}