UIScrollView现实自动循环滚动

 #import "RootViewController.h"
 
 #define width [UIScreen mainScreen].bounds.size.width
 #define heigthY 150
 #define scrollTime 1
 
 @interface RootViewController ()<UIScrollViewDelegate>
 {
     UIScrollView *_scrollView;
     NSMutableArray *imageArray;
     UIPageControl *pageControl;
 }
 @end
 
 @implementation RootViewController
 
 - (void)dealloc
 {
     imageArray = nil;
     [super dealloc];
 }
 
 - (void)loadView
 {
     [super loadView];
     _scrollView = [[UIScrollView alloc] initWithFrame:CGRectMake(, , width, heigthY)];
     _scrollView.pagingEnabled = YES;
     _scrollView.delegate = self;
     // 开始时选中第二个图片  图片的布局[3-1-2-3-1]
     _scrollView.contentOffset = CGPointMake(width, );
     // 隐藏水平滚动条
     _scrollView.showsHorizontalScrollIndicator = NO;
 
     pageControl = [[UIPageControl alloc] initWithFrame:CGRectMake(width - ,heigthY - , , )];
     // 设置pageControl不支持用户操作
     pageControl.userInteractionEnabled = NO;
     pageControl.currentPageIndicatorTintColor = [UIColor redColor];
     pageControl.pageIndicatorTintColor = [UIColor greenColor];
     [self.view addSubview:_scrollView];
     [self.view addSubview:pageControl];
     [_scrollView release];
     [pageControl release];
 
 }
 
 - (void)viewDidLoad {
     [super viewDidLoad];
     imageArray = [[NSMutableArray alloc] init];
     NSArray *tempArray = @[@"1-3.jpg",@"1-1.jpg",@"1-2.jpg",@"1-3.jpg",@"1-1.jpg"];
     [imageArray addObjectsFromArray:tempArray];
     // 根据imageArray的数量设置_scrollView的内容大小
     _scrollView.contentSize = CGSizeMake(width * imageArray.count, heigthY);
     pageControl.numberOfPages = imageArray.count - ;
     // 给_scrollView添加图片
     [self addImagesWithScrollView];
 
     // 添加定时器
     NSTimer *timer = [NSTimer scheduledTimerWithTimeInterval:scrollTime target:self selector:@selector(automateScroll) userInfo:nil repeats:YES];
 }
 
 // 每隔scrollTime秒就滚动一次
 - (void)automateScroll
 {
     // 因为开始时出现的图片是imageArray中的第二张图片，后面求余后还加1，使得contentOffset为2*width
     static int contentOffsetX = ;
     // 为了偏移量始终在(1 至 imageArray.count-2)*width中,((contentOffsetX % (imageArray.count - 2))求余得到的数值在 0~imageArray.count-3中, + 1后让数值保持在 1 至 imageArray.count-2 中
     _scrollView.contentOffset = CGPointMake(((contentOffsetX % (imageArray.count - )) + ) *width, );
     contentOffsetX ++;
     NSLog(@"==%d",contentOffsetX);
 }
 /**
  *  给scrollView添加图片
  */
 - (void)addImagesWithScrollView
 {
     for (int i = ; i < imageArray.count; i++) {
         UIImageView *imageView = [[UIImageView alloc] initWithImage:[UIImage imageNamed:imageArray[i]]];
         imageView.frame = CGRectMake(i * width, , width, heigthY);
         [_scrollView addSubview:imageView];
         [imageView release];
     }
 }
 
 //#pragma mark - UIScrollViewDelegate的方法
 - (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView
 {
     int imageIndex = scrollView.contentOffset.x / width;
     if (imageIndex == ) {
         // 滚到第一张图片时，就跳转到倒数第二张图片
         [_scrollView scrollRectToVisible:CGRectMake((imageArray.count - )*width, , width, heigthY) animated:NO];
     }else if (imageIndex == imageArray.count - ){
         // 滚动到最后一张图片时，就跳转到第二张图片
         [_scrollView scrollRectToVisible:CGRectMake(width, , width, heigthY) animated:NO];
     }
 }
 
 /**
  *  设置pageControl的当前页
  */
 - (void)scrollViewDidScroll:(UIScrollView *)scrollView
 {
     // 加0.5是为了用户体验好些，滑动过程中哪张图片占优就显示占优图片对应的下标
     int imageIndex = scrollView.contentOffset.x / width + 0.5;
     if (imageIndex == ) {
         // 设置相应的下标（使之减1后与pageControl的下标相对应）
         imageIndex = (int)imageArray.count - ;
     }else if (imageIndex == imageArray.count - ){
         // 设置相应的下标（使之减1后与pageControl的下标相对应）
         imageIndex = ;
     }
     pageControl.currentPage = imageIndex - ;
 }
 
 @end