三个imageView搞定左右轮播图

初始化scrollView让中间的imageView显示 照片数组的第1张
左边imageView显示照片数组的最后一张
右边imageView显示照片数组的第二张

//滚动视图懒加载
- (UIScrollView *)scrollView {
    
    if (!_scrollView) {
        // 开始创建滚动视图及属性
        _scrollView = [[UIScrollView alloc] initWithFrame:self.frame];
        _scrollView.contentSize = CGSizeMake(kWidth * self.imageArray.count, kHeight);
        _scrollView.delegate = self;
        _scrollView.pagingEnabled = YES;
        _scrollView.bounces = NO;
        _scrollView.bouncesZoom = NO;
        _scrollView.showsHorizontalScrollIndicator = NO;
        
#warning 初始的scrollView的偏移量
        _scrollView.contentOffset = CGPointMake(kWidth, 0);
        
    }
    return _scrollView;
}

//左边视图懒加载
- (UIImageView *)leftImageView {
    if (!_leftImageView) {
        
        //创建两个图片
        _leftImageView = [[UIImageView alloc] initWithFrame:CGRectMake(0, 0, kWidth, kHeight)];
        _leftImageView.image = self.imageArray[self.imageArray.count - 1];
    }
    return _leftImageView;
}

//右边视图懒加载
- (UIImageView *)rightImageView {
    
    if (!_rightImageView) {
        
        _rightImageView = [[UIImageView alloc] initWithFrame:CGRectMake(kWidth * 2, 0, kWidth, kHeight)];
        _rightImageView.image = self.imageArray[1];
    }
    return _rightImageView;
}

- (UIImageView *)moddileImage {
    if (!_moddileImage) {
        
        _moddileImage = [[UIImageView alloc] initWithFrame:CGRectMake(kWidth , 0, kWidth, kHeight)];
        _moddileImage.image = self.imageArray[0];
    }
    
    return _moddileImage;
}

//初始化方法
- (instancetype)initWithFrame:(CGRect)frame imageArray:(NSArray *)imageArray
{
    self = [super initWithFrame:frame];
    if (self) {
        
        self.rightIndex = 1;
        
        //给数组赋值
        self.imageArray = imageArray;
        
        self.leftIndex = self.imageArray.count - 1;
        
        //设置视图
        [self creatScrollView];
        
    }
    return self;
}

- (void)creatScrollView {
    [self startTimer];
    [self.scrollView addSubview:self.leftImageView];
    [self.scrollView addSubview:self.rightImageView];
    [self.scrollView addSubview:self.moddileImage];
    [self addSubview:self.scrollView];
    [self addSubview:self.pageControl];
}

核心代码片段

#pragma mark ---scrollView协议---
- (void)scrollViewDidScroll:(UIScrollView *)scrollView {
    //#define kWidth self.frame.size.width
    //scrollView的偏移量为kWidth * 2 代表的是往右偏移
    if (scrollView.contentOffset.x == kWidth * 2) {
        
        scrollView.contentOffset = CGPointMake(kWidth, 0);
        
        self.pageControl.currentPage = self.rightIndex;
        
        self.rightIndex++;

        if (self.rightIndex == self.imageArray.count) {
            
            self.rightIndex = 0;
            
        }
        self.moddileImage.image = self.rightImageView.image;
        
        self.rightImageView.image = self.imageArray[self.rightIndex];
        
        NSLog(@"--右边照片－－－－%ld", self.rightIndex);
        
        //左边照片比右边照片在数组中的下标少2
        self.leftIndex = self.rightIndex - 2;
        
        //往右偏移时左右imageView 的image 都要随时变更
        //当左边照片下标为－1时，代表的是：到数组最后一张照片
        if (self.leftIndex ==  -1) {
            self.leftIndex = self.imageArray.count - 1;
            
        }else if (self.leftIndex == -2) {//当左边照片下标为－2时，代表的是：到数组倒数第二张照片
            self.leftIndex = self.imageArray.count - 2;
        }
        
        self.leftImageView.image = self.imageArray[self.leftIndex];
        
        NSLog(@"----左边照片----%ld", self.leftIndex);
    }
    //scrollView的偏移量为0 代表的是往左偏移
    if (scrollView.contentOffset.x == 0) {
        
        scrollView.contentOffset = CGPointMake(kWidth, 0);
        
        self.pageControl.currentPage = self.leftIndex;
        
        self.leftIndex--;
        
        if (self.leftIndex < 0) {
            self.leftIndex = self.imageArray.count - 1;
        }
        
        NSLog(@"----左边照片----%ld", self.leftIndex);
        self.moddileImage.image = self.leftImageView.image;
        
        self.leftImageView.image = self.imageArray[self.leftIndex];
        
        //右边照片比左边照片在数组中的下标多2
        self.rightIndex = self.leftIndex + 2;
        
        //往左偏移时左右imageView 的image 都要随时变更
        //当右边照片下标为数组个数时，代表的是：到数组第一张照片
        if (self.rightIndex == self.imageArray.count) {
            self.rightIndex = 0;
        }else if (self.rightIndex == self.imageArray.count + 1) {//当右边照片下标为数组个数 ＋ 1时，代表的是：到数组第二张照片
            self.rightIndex = 1;
        }
        self.rightImageView.image = self.imageArray[self.rightIndex];
       
        NSLog(@"--右边照片－－－－%ld", self.rightIndex);
        
    }
}