下拉放大 上推隐藏

现在很多的app都有这个功能

先上效果图

#define IMAGEHEIGHT    200.0f

#define MAINSCREENWIDTH [UIScreen mainScreen].bounds.size.width

先添加两个UIImageView

//大图片

_zoomImageView = [[UIImageView alloc]initWithFrame:CGRectMake(0, 0, self.view.frame.size.width, IMAGEHEIGHT)];

_zoomImageView.image = [UIImage imageNamed:@"iPhone_personal_head_bg"];

_zoomImageView.contentMode = UIViewContentModeScaleAspectFill;

[self.view addSubview:_zoomImageView];

// 小图片

_littleImageView = [[UIImageView alloc] initWithFrame:CGRectMake(MAINSCREENWIDTH/2 - 50, 50, 100, 100)];

_littleImageView.image = [UIImage imageNamed:@"loadingIcon"];

[_zoomImageView addSubview:_littleImageView];

//添加一下渐变暗视图

_effectView = [[UIView alloc] initWithFrame:CGRectMake(0, 0, self.view.frame.size.width, IMAGEHEIGHT)];

_effectView.backgroundColor = [UIColor blackColor];

[_zoomImageView addSubview:_effectView];

//图片下是一个表格

//当滚动时动态计算高度

CGFloat changeY = 0.0;

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

CGFloat y = scrollView.contentOffset.y; //如果有导航控制器，这里应该加上导航控制器的高度64

changeY = y + 200;

NSLog(@"%lf",y);

if (y< -IMAGEHEIGHT) {

CGRect frame = _zoomImageView.frame;

frame.size.height = -y;

_zoomImageView.frame = _effectView.frame = frame;

CGPoint center = _littleImageView.center;

NSLog(@"changeY %lf",changeY);

center.y = 100-changeY/2;

_littleImageView.center = center;

}else{

_effectView.alpha = 1 + y/200;

}

changeY -= y;

}

这样就能简单实现上推隐藏 下拉放大 小图片大小不变的效果