iOS利用UIScrollView实现无限滚动效果

#import "ViewController.h"//屏幕宽度#define SCREEN_WIDTH [UIScreen mainScreen].bounds.size.width//图片高度#define IMG_HEIGHT 180//要显示的图片总数#define MAX_SIZE 7#import "ViewController.h"@interface ViewController () <UIScrollViewDelegate>//滚动视图@property (strong, nonatomic) UIScrollView *loopScrollView;//指示器@property (strong, nonatomic) UIPageControl *pageIndicator;//要展示的图片数组@property(strong, nonatomic) NSMutableArray *imgArray;@end@implementation ViewController//懒加载数组-(NSMutableArray *)imgArray{  if(_imgArray == nil)  {    _imgArray = [[NSMutableArray alloc]initWithCapacity:MAX_SIZE];    //在要展示的5张图片的前后各加一张图片，第一张前面加第五张，第五张后面加第一张    [_imgArray addObject:[UIImage imageNamed:@"img_05.jpg"]];    for (int i = 1; i< MAX_SIZE - 1; i++) {      NSString *imgName = [[NSString alloc]initWithFormat:@"img_0%d.jpg", i];      [_imgArray addObject:[UIImage imageNamed:imgName]];    }    [_imgArray addObject:[UIImage imageNamed:@"img_01.jpg"]];  }  return _imgArray;}- (void)viewDidLoad {  [super viewDidLoad];  [self setupScrollView];  [self setupPageControl];}/** * 创建UIScrollView并设置其属性 */-(void)setupScrollView{  UIScrollView *sc = [[UIScrollView alloc]initWithFrame:CGRectMake(0, 64, SCREEN_WIDTH, IMG_HEIGHT)];  //创建UIImageView并添加到UIScrollView中  for (int i = 0; i< MAX_SIZE; i++) {    UIImageView *img = [[UIImageView alloc]initWithImage:[self.imgArray objectAtIndex:i]];    img.frame = CGRectMake(SCREEN_WIDTH * i, 0, SCREEN_WIDTH, IMG_HEIGHT);    [sc addSubview:img];  }  //设置UIScrollView的属性  sc.contentSize = CGSizeMake(SCREEN_WIDTH * self.imgArray.count, IMG_HEIGHT);  sc.showsHorizontalScrollIndicator = NO;  sc.pagingEnabled = YES;  //刚开始应该滚动到第二张显示，因为第一张其实是最后一张图片  [sc setContentOffset:CGPointMake(SCREEN_WIDTH, 0) animated:NO];  //设置代理并添加到当前view中  sc.delegate = self;  [self.view addSubview:sc];  self.loopScrollView = sc;}/** * 创建UIPageControl并设置其属性 */-(void)setupPageControl{  //注意frame，这样设置可以居中显示  UIPageControl *pc = [[UIPageControl alloc]initWithFrame:CGRectMake(self.view.center.x - 50, CGRectGetMaxY(self.loopScrollView.frame) - 25 , 100, 25)];  //设置UIPageControl的属性并添加到当前view中  pc.numberOfPages = MAX_SIZE - 2;  pc.currentPage = 0;  pc.pageIndicatorTintColor = [UIColor redColor];  [self.view addSubview:pc];  self.pageIndicator = pc;}//UIScrollView的代理方法，在该方法中改变UIPageControl并且处理边缘滚动-(void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView{  //获取当前UIScrollView的位置  CGPoint offset = [scrollView contentOffset];  //算出滚动到第几页  int currentPage = offset.x/SCREEN_WIDTH;  //设置UIPageControl  self.pageIndicator.currentPage = currentPage - 1;  //对最后一张和第一张要进行特殊处理  //1、如果是第一张  if (currentPage == 0) {    //下面两个方法任选其一都可以达到效果，但是注意动画一定要设置为NO，不然会有视觉会有辣眼睛的感觉    //方法1    [self.loopScrollView setContentOffset:CGPointMake(SCREEN_WIDTH * (MAX_SIZE-2), 0) animated:NO];    //方法2，该方法要求设置contentSize时，任一方向就算不滚动也不能为0，否则无效    //[self.loopScrollView scrollRectToVisible:CGRectMake(SCREEN_WIDTH * (MAX_SIZE-2), 0, SCREEN_WIDTH, IMG_HEIGHT) animated:NO];    self.pageIndicator.currentPage = MAX_SIZE - 2;  }  //2、如果是最后一张  else if(currentPage == MAX_SIZE - 1) {    [self.loopScrollView setContentOffset:CGPointMake(SCREEN_WIDTH, 0) animated:NO];    //[self.loopScrollView scrollRectToVisible:CGRectMake(SCREEN_WIDTH, 0, SCREEN_WIDTH, IMG_HEIGHT) animated:NO];    self.pageIndicator.currentPage = 0;  }}@end