一、实现效果

实现图片的自动轮播

二、实现代码

storyboard中布局

代码：

 1 #import "YYViewController.h"  2  3 @interface YYViewController () <UIScrollViewDelegate>
 4 @property (weak, nonatomic) IBOutlet UIScrollView *scrollview;
 5 /**
 6  * 页码
 7 */  8 @property (weak, nonatomic) IBOutlet UIPageControl *pageControl;
 9  10 @property (nonatomic, strong) NSTimer *timer;
 11 @end  12  13 @implementation YYViewController
 14  15 - (void)viewDidLoad
 16 {
 17  [super viewDidLoad];
 18  19 // 图片的宽  20 CGFloat imageW = self.scrollview.frame.size.width;
 21 // CGFloat imageW = 300;
 22 // 图片高  23 CGFloat imageH = self.scrollview.frame.size.height;
 24 // 图片的Y  25 CGFloat imageY = 0;
 26 // 图片中数  27 NSInteger totalCount = 5;
 28 // 1.添加5张图片  29 for (int i = 0; i < totalCount; i++) {
 30 UIImageView *imageView = [[UIImageView alloc] init];
 31 // 图片X  32 CGFloat imageX = i * imageW;
 33 // 设置frame  34 imageView.frame = CGRectMake(imageX, imageY, imageW, imageH);
 35 // 设置图片  36 NSString *name = [NSString stringWithFormat:@"img_0%d", i + 1];
 37 imageView.image = [UIImage imageNamed:name];
 38 // 隐藏指示条  39 self.scrollview.showsHorizontalScrollIndicator = NO;
 40  41  [self.scrollview addSubview:imageView];
 42  }
 43  44 // 2.设置scrollview的滚动范围  45 CGFloat contentW = totalCount *imageW;
 46 //不允许在垂直方向上进行滚动  47 self.scrollview.contentSize = CGSizeMake(contentW, 0);
 48  49 // 3.设置分页  50 self.scrollview.pagingEnabled = YES;
 51  52 // 4.监听scrollview的滚动  53 self.scrollview.delegate = self;
 54  55  [self addTimer];
 56 }
 57  58 - (void)nextImage
 59 {
 60 int page = (int)self.pageControl.currentPage;
 61 if (page == 4) {
 62 page = 0;
 63 }else  64  {
 65 page++;
 66  }
 67  68 // 滚动scrollview  69 CGFloat x = page * self.scrollview.frame.size.width;
 70 self.scrollview.contentOffset = CGPointMake(x, 0);
 71 }
 72  73 // scrollview滚动的时候调用  74 - (void)scrollViewDidScroll:(UIScrollView *)scrollView
 75 {
 76 NSLog(@"滚动中");
 77 // 计算页码
 78 // 页码 = (contentoffset.x + scrollView一半宽度)/scrollView宽度  79 CGFloat scrollviewW = scrollView.frame.size.width;
 80 CGFloat x = scrollView.contentOffset.x;
 81 int page = (x + scrollviewW / 2) / scrollviewW;
 82 self.pageControl.currentPage = page;
 83 }
 84  85 // 开始拖拽的时候调用  86 - (void)scrollViewWillBeginDragging:(UIScrollView *)scrollView
 87 {
 88 // 关闭定时器(注意点; 定时器一旦被关闭,无法再开启)
 89 // [self.timer invalidate];  90  [self removeTimer];
 91 }
 92  93 - (void)scrollViewDidEndDragging:(UIScrollView *)scrollView willDecelerate:(BOOL)decelerate
 94 {
 95 // 开启定时器  96  [self addTimer];
 97 }
 98  99 /**
100  * 开启定时器
101 */ 102 - (void)addTimer{
103 104 self.timer = [NSTimer scheduledTimerWithTimeInterval:1 target:self selector:@selector(nextImage) userInfo:nil repeats:YES];
105 106 }
107 /**
108  * 关闭定时器
109 */ 110 - (void)removeTimer
111 {
112  [self.timer invalidate];
113 }
114 @end

提示：以下两个属性已经和storyboard中的控件进行了连线。

@property (weak, nonatomic) IBOutletUIScrollView *scrollview;

@property (weak, nonatomic) IBOutletUIPageControl *pageControl;

补充：定时器NSTimer

定时器 适合用来隔一段时间做一些间隔比较长的操作

NSTimeInterval:多长多件操作一次

target :操作谁

selector : 要操作的方法

userInfo: 传递参数

repeats: 是否重复

self.timer = [NSTimer scheduledTimerWithTimeInterval:1 target:self selector:@selector(nextImage) userInfo:nil repeats:YES];