使用UIScrollView 结合 UIImageView 实现图片循环滚动

场景：

在开发工作中，有时我们需要实现一组图片循环滚动的情况。当我们使用 UIScrollView 结合 UIImageView 来实现时，一般 UIImageView 会尽量考虑重用，下面例子是以（左中右）三个 UIImageView 的使用，其实也可以考虑使用 两个 UIImageView 实现的情况。这样避免 一组图片多少个就对应多少个 UIImageView 所导致占用过多内存的情况。

效果如下：

ViewController.h

 #import <UIKit/UIKit.h>

 @interface ViewController : UIViewController <UIScrollViewDelegate>
 @property (strong, nonatomic) UIScrollView *scrV;
 @property (strong, nonatomic) UIPageControl *pageC;
 @property (strong, nonatomic) UIImageView *imgVLeft;
 @property (strong, nonatomic) UIImageView *imgVCenter;
 @property (strong, nonatomic) UIImageView *imgVRight;
 @property (strong, nonatomic) UILabel *lblImageDesc;
 @property (strong, nonatomic) NSMutableDictionary *mDicImageData;
 @property (assign, nonatomic) NSUInteger currentImageIndex;
 @property (assign, nonatomic) NSUInteger imageCount;

 @end

ViewController.m

 #import "ViewController.h"

 #define kWidthOfScreen [[UIScreen mainScreen] bounds].size.width
 #define kHeightOfScreen [[UIScreen mainScreen] bounds].size.height
 #define kImageViewCount 3
 @interface ViewController ()
 /**
  *  加载图片数据
  */
 - (void)loadImageData;

 /**
  *  添加滚动视图
  */
 - (void)addScrollView;

 /**
  *  添加三个图片视图到滚动视图内
  */
 - (void)addImageViewsToScrollView;

 /**
  *  添加分页控件
  */
 - (void)addPageControl;

 /**
  *  添加标签；用于图片描述
  */
 - (void)addLabel;

 /**
  *  根据当前图片索引设置信息
  *
  *  @param currentImageIndex 当前图片索引；即中间
  */
 - (void)setInfoByCurrentImageIndex:(NSUInteger)currentImageIndex;

 /**
  *  设置默认信息
  */
 - (void)setDefaultInfo;

 /**
  *  重新加载图片
  */
 - (void)reloadImage;

 - (void)layoutUI;
 @end

 @implementation ViewController

 - (void)viewDidLoad {
     [super viewDidLoad];

     [self layoutUI];
 }

 - (void)didReceiveMemoryWarning {
     [super didReceiveMemoryWarning];
     // Dispose of any resources that can be recreated.
 }

 - (void)loadImageData {
     NSString *path = [[NSBundle mainBundle] pathForResource:@"ImageInfo" ofType:@"plist"];
     _mDicImageData = [NSMutableDictionary dictionaryWithContentsOfFile:path];
     _imageCount = _mDicImageData.count;
 }

 - (void)addScrollView {
     _scrV = [[UIScrollView alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
     _scrV.contentSize = CGSizeMake(kWidthOfScreen * kImageViewCount, kHeightOfScreen);
     _scrV.contentOffset = CGPointMake(kWidthOfScreen, 0.0);
     _scrV.pagingEnabled = YES;
     _scrV.showsHorizontalScrollIndicator = NO;
     _scrV.delegate = self;
     [self.view addSubview:_scrV];
 }

 - (void)addImageViewsToScrollView {
     //图片视图；左边
     _imgVLeft = [[UIImageView alloc] initWithFrame:CGRectMake(0.0, 0.0, kWidthOfScreen, kHeightOfScreen)];
     _imgVLeft.contentMode = UIViewContentModeScaleAspectFit;
     [_scrV addSubview:_imgVLeft];

     //图片视图；中间
     _imgVCenter = [[UIImageView alloc] initWithFrame:CGRectMake(kWidthOfScreen, 0.0, kWidthOfScreen, kHeightOfScreen)];
     _imgVCenter.contentMode = UIViewContentModeScaleAspectFit;
     [_scrV addSubview:_imgVCenter];

     //图片视图；右边
     _imgVRight = [[UIImageView alloc] initWithFrame:CGRectMake(kWidthOfScreen * 2.0, 0.0, kWidthOfScreen, kHeightOfScreen)];
     _imgVRight.contentMode = UIViewContentModeScaleAspectFit;
     [_scrV addSubview:_imgVRight];
 }

 - (void)addPageControl {
     _pageC = [UIPageControl new];
     CGSize size= [_pageC sizeForNumberOfPages:_imageCount]; //根据页数返回 UIPageControl 合适的大小
     _pageC.bounds = CGRectMake(0.0, 0.0, size.width, size.height);
     _pageC.center = CGPointMake(kWidthOfScreen / 2.0, kHeightOfScreen - 80.0);
     _pageC.numberOfPages = _imageCount;
     _pageC.pageIndicatorTintColor = [UIColor whiteColor];
     _pageC.currentPageIndicatorTintColor = [UIColor brownColor];
     _pageC.userInteractionEnabled = NO; //设置是否允许用户交互；默认值为 YES，当为 YES 时，针对点击控件区域左（当前页索引减一，最小为0）右（当前页索引加一，最大为总数减一），可以编写 UIControlEventValueChanged 的事件处理方法
     [self.view addSubview:_pageC];
 }

 - (void)addLabel {
     _lblImageDesc = [[UILabel alloc] initWithFrame:CGRectMake(0.0, 40.0, kWidthOfScreen, 40.0)];
     _lblImageDesc.textAlignment = NSTextAlignmentCenter;
     _lblImageDesc.textColor = [UIColor whiteColor];
     _lblImageDesc.font = [UIFont boldSystemFontOfSize:[UIFont labelFontSize]];
     _lblImageDesc.text = @"Fucking now.";
     [self.view addSubview:_lblImageDesc];
 }

 - (void)setInfoByCurrentImageIndex:(NSUInteger)currentImageIndex {
     NSString *currentImageNamed = [NSString stringWithFormat:@"%lu.png", (unsigned long)currentImageIndex];
     _imgVCenter.image = [UIImage imageNamed:currentImageNamed];
     _imgVLeft.image = [UIImage imageNamed:[NSString stringWithFormat:@"%lu.png", (unsigned long)((_currentImageIndex -  + _imageCount) % _imageCount)]];
     _imgVRight.image = [UIImage imageNamed:[NSString stringWithFormat:@"%lu.png", (unsigned long)((_currentImageIndex + ) % _imageCount)]];

     _pageC.currentPage = currentImageIndex;
     _lblImageDesc.text = _mDicImageData[currentImageNamed];
 }

 - (void)setDefaultInfo {
     _currentImageIndex = ;
     [self setInfoByCurrentImageIndex:_currentImageIndex];
 }

 - (void)reloadImage {
     CGPoint contentOffset = [_scrV contentOffset];
     if (contentOffset.x > kWidthOfScreen) { //向左滑动
         _currentImageIndex = (_currentImageIndex + ) % _imageCount;
     } else if (contentOffset.x < kWidthOfScreen) { //向右滑动
         _currentImageIndex = (_currentImageIndex -  + _imageCount) % _imageCount;
     }

     [self setInfoByCurrentImageIndex:_currentImageIndex];
 }

 - (void)layoutUI {
     self.view.backgroundColor = [UIColor blackColor];

     [self loadImageData];
     [self addScrollView];
     [self addImageViewsToScrollView];
     [self addPageControl];
     [self addLabel];
     [self setDefaultInfo];
 }

 #pragma mark - UIScrollViewDelegate
 - (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView {
     [self reloadImage];

     _scrV.contentOffset = CGPointMake(kWidthOfScreen, 0.0);
     _pageC.currentPage = _currentImageIndex;

     NSString *currentImageNamed = [NSString stringWithFormat:@"%lu.png", (unsigned long)_currentImageIndex];
     _lblImageDesc.text = _mDicImageData[currentImageNamed];
 }

 @end

​ImageInfo.plist

 <?xml version="1.0" encoding="UTF-8"?>
 <!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
 <plist version="1.0">
 <dict>
     <key>0.png</key>
     <string>WATCH，它，终于来了。</string>
     <key>1.png</key>
     <string>iPhone 6，无双，有此一双。</string>
     <key>2.png</key>
     <string>MacBook，轻于时代，先于时代。</string>
     <key>3.png</key>
     <string>iPad Air 2，轻轻地，改变一切。</string>
     <key>4.png</key>
     <string>iOS 9，它，将要到来。</string>
 </dict>
 </plist>