以下图为例，图片，红色view和蓝色view是添加在scrollView上的，向上拖动，红色view停留在屏幕顶端不动，其它的继续滚动，向下拖动后，红色view跟着下来

代码如下:(注意的是scrollView中自动布局的设置问题)

1 #import "ViewController.h" 2 @interface ViewController () 
     
       3 @property (weak, nonatomic) IBOutlet UIScrollView *scrollView; 4 @property (weak, nonatomic) IBOutlet UIView *blueView; 5 @property (weak, nonatomic) IBOutlet UIView *redView; 6 @property (weak, nonatomic) IBOutlet UIImageView *imageView; 7 @end 8 @implementation ViewController 9 - (void)viewDidLoad {10     [super viewDidLoad];11     self.scrollView.contentSize = CGSizeMake(0, CGRectGetMaxY(self.blueView.frame));12 }13 14 - (void)scrollViewDidScroll:(UIScrollView *)scrollView15 {16     CGFloat imageH = self.imageView.frame.size.height;17     CGFloat offsetY = scrollView.contentOffset.y;18     if (offsetY >= imageH) {19         //将红色控件添加到控制器View中20         CGRect redFrame = self.redView.frame;21         redFrame.origin.y = 0;22         self.redView.frame = redFrame;23         [self.view addSubview:self.redView];24     }else {25         //将红色控件添加到控制器scrollView中26         CGRect redFrame = self.redView.frame;27         redFrame.origin.y = 140;28         self.redView.frame = redFrame;29         [self.scrollView addSubview:self.redView];30     }31     32 //    if (offsetY < 0) {33 //        CGFloat scale = 1 - (offsetY / 80);34 //        self.imageView.transform = CGAffineTransformMakeScale(scale, scale);35 //    }36     37     CGFloat scale = 1 - (offsetY / 20);38     scale = (scale >= 1) ? scale : 1;39     self.imageView.transform = CGAffineTransformMakeScale(scale, scale);40 }41 @end