UITableView隐藏header

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