加上这段代码即可
func scrollViewDidScroll(scrollView:UIScrollView) {
let sectionHeaderHeight:CGFloat = 55
if scrollView.contentOffset.y <= sectionHeaderHeight && scrollView.contentOffset.y > 0 {
scrollView.contentInset =UIEdgeInsetsMake(-scrollView.contentOffset.y, 0, 0, 0)
}
elseif scrollView.contentOffset.y >= sectionHeaderHeight {
scrollView.contentInset =UIEdgeInsetsMake(-sectionHeaderHeight, 0, 0, 0)
}
}