iOS 禁止UITableView区头滚动

- (void)scrollViewDidScroll:(UIScrollView *)scrollView{    CGFloat sectionHeaderHeight = 50;    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);        }    }}