去掉section的headview粘性

- (void)scrollViewDidScroll:(UIScrollView *)scrollView

{

    CGFloat sectionHeaderHeight = 40;

    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);

    }

}