1）@property(nonatomic) BOOL bounces;  设置UIScrollView是否需要弹簧效果

 1 #import "MJViewController.h"
 2  3 @interface MJViewController ()  4 {  5 //在私有扩展中创建一个属性  6 UIScrollView *_scrollView;  7 }  8 @end  9 10 @implementation MJViewController 11 12 - (void)viewDidLoad 13 { 14  [super viewDidLoad]; 15 16 // 1.创建UIScrollView 17 UIScrollView *scrollView = [[UIScrollView alloc] init]; 18 scrollView.frame = CGRectMake(0, 0, 250, 250); // frame中的size指UIScrollView的可视范围 19 scrollView.backgroundColor = [UIColor grayColor]; 20  [self.view addSubview:scrollView]; 21 22 // 2.创建UIImageView（图片） 23 UIImageView *imageView = [[UIImageView alloc] init]; 24 imageView.image = [UIImage imageNamed:@"big.jpg"]; 25 CGFloat imgW = imageView.image.size.width; // 图片的宽度 26 CGFloat imgH = imageView.image.size.height; // 图片的高度 27 imageView.frame = CGRectMake(0, 0, imgW, imgH); 28  [scrollView addSubview:imageView]; 29 30 // 3.设置scrollView的属性 31 32 // 设置UIScrollView的滚动范围（内容大小） 33 scrollView.contentSize = imageView.image.size; 34 35 // 隐藏水平滚动条 36 scrollView.showsHorizontalScrollIndicator = NO; 37 scrollView.showsVerticalScrollIndicator = NO; 38 39 // 用来记录scrollview滚动的位置 40 // scrollView.contentOffset = ; 41 42 // 去掉弹簧效果 43 // scrollView.bounces = NO; 44 45 // 增加额外的滚动区域（逆时针，上、左、下、右） 46 // top left bottom right 47 scrollView.contentInset = UIEdgeInsetsMake(20, 20, 20, 20); 48 49 _scrollView = scrollView; 50 } 51 52 - (IBAction)down:(UIButton *)sender { 53 [UIView animateWithDuration:1.0 animations:^{ 54 //三个步骤 55 CGPoint offset = _scrollView.contentOffset; 56 offset.y += 150; 57 _scrollView.contentOffset = offset; 58 59 //_scrollView.contentOffset = CGPointMake(0, 0); 60  }]; 61 } 62 @end