section的headerview或者footerview會黏在屏幕的頂端或者下端，不會跟著tableview一起整體滾動
- (void)scrollViewDidScroll:(UIScrollView *)sender {
? if(sender == _myTab) {
? ? ? CGFloat sectionHeaderHeight = 30;
? ? ? if (sender.contentOffset.y<=sectionHeaderHeight&&sender.contentOffset.y>=0){
? ? ? ? ? ? ?sender.contentInset = UIEdgeInsetsMake(-sender.contentOffset.y, 0, 0, 0);
? ? ?} else if (sender.contentOffset.y>=sectionHeaderHeight) {
? ? ? ? ? ? sender.contentInset = UIEdgeInsetsMake(-sectionHeaderHeight, 0, 0, 0);
? ? }
? }
}
