去掉UItableview headerview黏性(sticky)

- (void)scrollViewDidScroll:(UIScrollView *)scrollView {
  if (scrollView == self.tableView)
  {
      CGFloat sectionHeaderHeight = 64; //sectionHeaderHeight
      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);
      }
  }
}