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 @end9
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