tableView下拉放大头部视图

//先实现 UIScrollViewDelegate  代理

//headVIewHeight : tableview 的头试图高度

//headView  : tableView 的头视图

- (void)scrollViewDidScroll:(UIScrollView *)scrollView {

    CGFloat yOffset =tbView.contentOffset.y;

    CGFloat nowHeight =fabs(yOffset) + headVIewHeight;

    CGFloat nowWid = (nowHeight /headVIewHeight) *kDeviceWidth;

     if (yOffset <0)

        {

 [headView setFrame:CGRectMake(-(nowWid -kDeviceWidth) / 2.0,-(nowHeight -headVIewHeight), nowWid, nowHeight)

        }

 ｝