三张图片轮播器<ios>

HmImgCell.h
#import <UIKit/UIKit.h>

@interface HmImgCell : UICollectionViewCell
@property(nonatomic,strong)NSIndexPath*indexPath;
@property(nonatomic,strong)UIImage*img;
@end
//.m
#import "HmImgCell.h"
@interface HmImgCell()
@property (weak, nonatomic) IBOutlet UIImageView *iconView;

@property (weak, nonatomic) IBOutlet UILabel *textView;

@end
@implementation HmImgCell
-(void)setImg:(UIImage *)img{
    _img=img;
    self.iconView.image=img;

}
-(void)setIndexPath:(NSIndexPath *)indexPath{
    _indexPath=indexPath;
    self.textView.text=[NSString stringWithFormat:@"%ld---%ld",indexPath.section,indexPath.item];

}
@end
///ViewController
//.m
#import "ViewController.h"
#import "HmImgCell.h"
#define cnt 9
@interface ViewController ()
@property (weak, nonatomic) IBOutlet UICollectionViewFlowLayout *layout;
@property(nonatomic,assign)NSInteger currentIndex;
@property(nonatomic,strong)NSArray* imgs;
@end
@implementation ViewController

//实现懒加载
-(NSArray*)imgs{
    if (_imgs==nil) {
        NSMutableArray*arr=[NSMutableArray arrayWithCapacity:cnt];
        for (int i=0; i<cnt; i++) {
//            把数据包装
            NSString*imgName=[NSString stringWithFormat:@"%d",i];
            UIImage*img=[UIImage imageNamed:imgName];
            [arr addObject:img];
        }
        _imgs=arr;
    }
    return _imgs;
}
- (void)viewDidLoad {
    [super viewDidLoad];
//设置layout的属性
    self.layout.itemSize=self.collectionView.frame.size;
    self.layout.minimumLineSpacing=0;
    self.layout.scrollDirection=UICollectionViewScrollDirectionHorizontal;
    self.collectionView.pagingEnabled=YES;
    self.collectionView.bounces=NO;
//设置动画
    NSTimer*time=[NSTimer timerWithTimeInterval:2 target:self selector:@selector(nextImg) userInfo:nil repeats:YES];
    NSRunLoop*run=[NSRunLoop currentRunLoop];
    [run addTimer:time forMode:NSRunLoopCommonModes];
//    先让scolleView滚动到索引为一的位置
    NSIndexPath*indexPath=[NSIndexPath indexPathForItem:1 inSection:0];
    [self.collectionView scrollToItemAtIndexPath:indexPath atScrollPosition:UICollectionViewScrollPositionNone animated:NO];
}
//设置下一张图片方法
-(void)nextImg{
//让图片滚动到原来索引为1的位置
    [self.collectionView setContentOffset:CGPointMake(self.collectionView.frame.size.width*2, 0) animated:YES];
}
//确定多少item
-(NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section{
    return self.imgs.count;
}
//确定每行展示的cell
-(UICollectionViewCell*)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath{
    HmImgCell*cell=[collectionView dequeueReusableCellWithReuseIdentifier:@"img" forIndexPath:indexPath];
//   获取当前需要展示图片的索引
    
    NSInteger index=(indexPath.item-1+cnt+self.currentIndex)%cnt;
//赋值
    cell.img=self.imgs[index];
    cell.indexPath=indexPath;
    return cell;

}
//当拖拽停止时调用的方法
-(void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView{
//让图片回到原来的位置
    
//    计算当前偏移量的索引
        NSInteger offsetIndex=(self.collectionView.contentOffset.x)/self.collectionView.frame.size.width-1;
//    当前位置的偏移量
    self.currentIndex=(offsetIndex+cnt+self.currentIndex)%cnt;
    NSIndexPath*index=[NSIndexPath indexPathForItem:1 inSection:0];
    [self.collectionView scrollToItemAtIndexPath:index atScrollPosition:UICollectionViewScrollPositionNone animated:NO];
//关闭动画
    [UIView setAnimationsEnabled:NO];
//    刷新当前图片
    [self.collectionView reloadItemsAtIndexPaths:@[index]];
//开启动画
    [UIView setAnimationsEnabled:YES];
}
//当开启动画停止滚动时用上面的方法
-(void)scrollViewDidEndScrollingAnimation:(UIScrollView *)scrollView{

    [self scrollViewDidEndDecelerating:scrollView];
}
@end