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：

#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</uiscrollviewdelegate></uikit>

#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 - 1 + _imageCount) % _imageCount)]];      _imgVRight.image = [UIImage imageNamed:[NSString stringWithFormat:@"%lu.png", (unsigned long)((_currentImageIndex + 1) % _imageCount)]];             _pageC.currentPage = currentImageIndex;      _lblImageDesc.text = _mDicImageData[currentImageNamed];  }     - (void)setDefaultInfo {      _currentImageIndex = 0;      [self setInfoByCurrentImageIndex:_currentImageIndex];  }     - (void)reloadImage {      CGPoint contentOffset = [_scrV contentOffset];      if (contentOffset.x > kWidthOfScreen) { //向左滑动          _currentImageIndex = (_currentImageIndex + 1) % _imageCount;      } else if (contentOffset.x < kWidthOfScreen) { //向右滑动          _currentImageIndex = (_currentImageIndex - 1 + _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