iOS开发-UITableView顶部图片下拉放大

关于顶部图片下拉放大，设置UITableView的headerView实现，UITableView继承自UIScrollView，同样的设置UIScrollView的顶部图片也可以实现同样的效果

这里使用Xib创建HerderView:

1、声明：
@property   (strong,nonatomic) CityFaceBookHearView *CityFaceBookHeaderView;

2、懒加载初始化
-(CityFaceBookHearView *)CityFaceBookHeaderView{
    if (_CityFaceBookHeaderView == nil) {
        _CityFaceBookHeaderView = [[[NSBundle mainBundle] loadNibNamed:@"CityFaceBookHearView" owner:0 options:nil]lastObject];
    }
    return _CityFaceBookHeaderView;
}
3、关联
 self.CityFaceBookHeaderView.bgImageView.clipsToBounds=YES;
 self.CityFaceBookHeaderView.bgImageView.contentMode=UIViewContentModeScaleAspectFill;
 self.CityFaceBookHeaderView.bgImageView.image = [UIImage imageNamed:@"Default@180"]; // 默认图
 self.tableView.tableHeaderView=self.CityFaceBookHeaderView;
4、数据刷新
[self.CityFaceBookHeaderView configWithData:_dataHeaderViewModel didSelectSaygoodBtnBlock:^{
  // do something
}];
5、UIScrollViewDelegate
- (void)scrollViewDidScroll:(UIScrollView *)scrollView
{
    CGFloat offsetY = scrollView.contentOffset.y;
    if (offsetY < 0) {
        self.CityFaceBookHeaderView.bgImageView.frame = CGRectMake(offsetY/2, offsetY, _CityFaceBookHeaderView.width - offsetY, _CityFaceBookHeaderView.height - offsetY);  // 修改头部的frame值就行了
    }
}