实现拖动列表时放大列表顶部的图片

学习网站

http://jingyan.baidu.com/album/fdffd1f85a3a4af3e98ca13c.html?picindex=1

主要代码

//变焦图片作为底层
@property(nonatomic,strong)UIImageView *spaceImgView;

  //设置变焦图片的大小和位置
        [_spaceImgView sd_setImageWithURL:[NSURL URLWithString:urlString]];
        _spaceImgView.frame = CGRectMake(0, -imageHeight, kUIScreenWidth , imageHeight);
       // _spaceImgView.userInteractionEnabled = YES;
        
        //设置图片的高度和宽度都改变(必须设置,否则只有高度改变)
        _spaceImgView.contentMode = UIViewContentModeScaleAspectFill;
        
        //将图片加入集合视图上
        [self.collectionView addSubview:_spaceImgView];

-(void)scrollViewDidScroll:(UIScrollView *)scrollView{
    CGFloat y = scrollView.contentOffset.y;
    if (y<-imageHeight) {
        CGRect frame = _spaceImgView.frame;
        frame.origin.y = y;
        frame.size.height = -y;
        _spaceImgView.frame = frame;
    }
    
}