ScrollView中的圖片無限循環(huán)一直是現在APP中常用的構造。
.h文件中

#import <UIKit/UIKit.h>

@interface ScrollView : UIView

@property(nonatomic,strong) NSArray *imageArray;

@end

.m文件

#import "ScrollView.h"
//屏幕的寬度
#define kScreenW [UIScreen mainScreen].bounds.size.width
//設置UIScrollView的代理
@interface ScrollView () <UIScrollViewDelegate>{
    
    //UIScrollView 滑動視圖
    UIScrollView *_scrollView ;
    //頁面控制器視圖
    UIPageControl *_pageControl;
    
    /**
     *  三張圖片視圖刷袍，左 中 右 
        實現無限循環(huán)
     */
    
    UIImageView *_middleImage;
    UIImageView *_leftImage;
    UIImageView *_rightImage;
    
    //索引值 就當做是數組的下標
    NSInteger _index;
}

@end

@implementation ScrollView

//覆寫initWithFrame
- (instancetype)initWithFrame:(CGRect)frame {
    
    //設置初始下標
    _index = 0;
    self = [super initWithFrame:frame];
    if (self != nil) {
        
    }
    
    return self;
}

//這里是獲取數據的
- (void)setImageArray:(NSArray *)imageArray {
    
    _imageArray = imageArray;
    //創(chuàng)建View
    [self loadImage];
}



- (void)loadImage {
    //本視圖的高度--》將來是要被ViewController調用的
    CGFloat height = self.frame.size.height;
    
    //大小 位置
    _scrollView = [[UIScrollView alloc] initWithFrame:CGRectMake(0, 0, kScreenW, height)];
    //分頁功能
    _scrollView.pagingEnabled = YES;
    //隱藏滑塊
    _scrollView.showsHorizontalScrollIndicator = NO;
    _scrollView.showsVerticalScrollIndicator = NO;
    //代理代咸，都懂的
    _scrollView.delegate = self;
    //滑動區(qū)域，因為只有三個imageView所以只需要三個屏幕寬度
    _scrollView.contentSize = CGSizeMake(3*kScreenW, height);
    //增加一個屏幕的寬度為第一次看到的視圖剛好是中間視圖
     _scrollView.contentOffset = CGPointMake(kScreenW, 0);
  
    [self addSubview:_scrollView];
    
    //頁面控制的基本設置
    _pageControl = [[UIPageControl alloc] initWithFrame:CGRectMake(0, height - 35, kScreenW, 35)];
    _pageControl.numberOfPages = _imageArray.count;
    _pageControl.currentPage = 0;
    
    //設置三個imageView
    _leftImage = [[UIImageView alloc] initWithFrame:CGRectMake(0, 0, kScreenW, height)];
    
    _middleImage = [[UIImageView alloc] initWithFrame:CGRectMake(kScreenW, 0, kScreenW, height)];
    
    _rightImage = [[UIImageView alloc] initWithFrame:CGRectMake(kScreenW *2, 0, kScreenW, height)];
    [_scrollView addSubview:_leftImage];
    [_scrollView addSubview:_rightImage];
    [_scrollView addSubview:_middleImage];
    
    
    [self addSubview:_pageControl];
    //設置圖片
    [self loadImageView];
    
    
}
- (void)loadImageView {
    
    //上一張
    NSInteger leftIndex = (_index - 1 + _imageArray.count) % _imageArray.count;

    _leftImage.image = [UIImage imageNamed:_imageArray[leftIndex]];
    
    //當前頁圖片
    _middleImage.image = [UIImage imageNamed:_imageArray[_index]];
    
    //下一張
    NSInteger rightIndex = (_index + 1) %_imageArray.count;
    
    _rightImage.image = [UIImage imageNamed:_imageArray[rightIndex]];
    
    
    
}

//當完成滑動減速調用的方法
- (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView {
    //往左滑 --> 下一張
    if (scrollView.contentOffset.x > kScreenW) {
        //數組下標
        _index =(_index + 1) %_imageArray.count;
        //往右滑
    }else if(scrollView.contentOffset.x < kScreenW){
        
        _index = (_index - 1 + _imageArray.count) % _imageArray.count;
    }
    
    //重新設置圖片
    [self loadImageView];
    //設置偏移區(qū)間
    scrollView.contentOffset = CGPointMake(kScreenW, 0);
    
    //頁面控制器的點點的變化
    _pageControl.currentPage = (_index ) %_imageArray.count;
    
}
@end