如何使tableView的组头不悬停

原理：
该方法，其实是将tableView的contentInset向上挪动了一个组头的高度，因此，并不是实际意义上的将组头给干掉了，而是把显示组头视图的位置向上挪动了个组头的高度，
挪出了眼睛的可视距离之外，因此，实现了取消组头粘滞性的效果。

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

以下是组头组尾都不悬停：

- (void)scrollViewDidScroll:(UIScrollView *)scrollView {
    
    CGFloat sectionHeaderHeight = MZScreenScale(40);
    CGFloat sectionFooterHeight = MZScreenScale(10);
    CGFloat offsetY = scrollView.contentOffset.y;
    if (offsetY >= 0 && offsetY <= sectionHeaderHeight) {
        scrollView.contentInset = UIEdgeInsetsMake(-offsetY, 0, -sectionFooterHeight, 0);
    } else if (offsetY >= sectionHeaderHeight && offsetY <= scrollView.contentSize.height - scrollView.frame.size.height - sectionFooterHeight) {
        scrollView.contentInset = UIEdgeInsetsMake(-sectionHeaderHeight, 0, -sectionFooterHeight, 0);
    } else if (offsetY >= scrollView.contentSize.height - scrollView.frame.size.height - sectionFooterHeight && offsetY <= scrollView.contentSize.height - scrollView.frame.size.height) {
        scrollView.contentInset = UIEdgeInsetsMake(-offsetY, 0, -(scrollView.contentSize.height - scrollView.frame.size.height - sectionFooterHeight), 0);
    }
}