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

 1 #import <UIKit/UIKit.h>  2   3 @interface ViewController : UIViewController <UIScrollViewDelegate>  4 @property (strong, nonatomic) UIScrollView *scrV;  5 @property (strong, nonatomic) UIPageControl *pageC;  6 @property (strong, nonatomic) UIImageView *imgVLeft;  7 @property (strong, nonatomic) UIImageView *imgVCenter;  8 @property (strong, nonatomic) UIImageView *imgVRight;  9 @property (strong, nonatomic) UILabel *lblImageDesc; 10 @property (strong, nonatomic) NSMutableDictionary *mDicImageData; 11 @property (assign, nonatomic) NSUInteger currentImageIndex; 12 @property (assign, nonatomic) NSUInteger imageCount; 13  14 @end

ViewController.m

  1 #import "ViewController.h"   2    3 #define kWidthOfScreen [[UIScreen mainScreen] bounds].size.width   4 #define kHeightOfScreen [[UIScreen mainScreen] bounds].size.height   5 #define kImageViewCount 3   6 @interface ViewController ()   7 /**   8  *  加载图片数据   9  */  10 - (void)loadImageData;  11   12 /**  13  *  添加滚动视图  14  */  15 - (void)addScrollView;  16   17 /**  18  *  添加三个图片视图到滚动视图内  19  */  20 - (void)addImageViewsToScrollView;  21   22 /**  23  *  添加分页控件  24  */  25 - (void)addPageControl;  26   27 /**  28  *  添加标签；用于图片描述  29  */  30 - (void)addLabel;  31   32 /**  33  *  根据当前图片索引设置信息  34  *  35  *  @param currentImageIndex 当前图片索引；即中间  36  */  37 - (void)setInfoByCurrentImageIndex:(NSUInteger)currentImageIndex;  38   39 /**  40  *  设置默认信息  41  */  42 - (void)setDefaultInfo;  43   44 /**  45  *  重新加载图片  46  */  47 - (void)reloadImage;  48   49 - (void)layoutUI;  50 @end  51   52 @implementation ViewController  53   54 - (void)viewDidLoad {  55     [super viewDidLoad];  56       57     [self layoutUI];  58 }  59   60 - (void)didReceiveMemoryWarning {  61     [super didReceiveMemoryWarning];  62     // Dispose of any resources that can be recreated.  63 }  64   65 - (void)loadImageData {  66     NSString *path = [[NSBundle mainBundle] pathForResource:@"ImageInfo" ofType:@"plist"];  67     _mDicImageData = [NSMutableDictionary dictionaryWithContentsOfFile:path];  68     _imageCount = _mDicImageData.count;  69 }  70   71 - (void)addScrollView {  72     _scrV = [[UIScrollView alloc] initWithFrame:[[UIScreen mainScreen] bounds]];  73     _scrV.contentSize = CGSizeMake(kWidthOfScreen * kImageViewCount, kHeightOfScreen);  74     _scrV.contentOffset = CGPointMake(kWidthOfScreen, 0.0);  75     _scrV.pagingEnabled = YES;  76     _scrV.showsHorizontalScrollIndicator = NO;  77     _scrV.delegate = self;  78     [self.view addSubview:_scrV];  79 }  80   81 - (void)addImageViewsToScrollView {  82     //图片视图；左边  83     _imgVLeft = [[UIImageView alloc] initWithFrame:CGRectMake(0.0, 0.0, kWidthOfScreen, kHeightOfScreen)];  84     _imgVLeft.contentMode = UIViewContentModeScaleAspectFit;  85     [_scrV addSubview:_imgVLeft];  86       87     //图片视图；中间  88     _imgVCenter = [[UIImageView alloc] initWithFrame:CGRectMake(kWidthOfScreen, 0.0, kWidthOfScreen, kHeightOfScreen)];  89     _imgVCenter.contentMode = UIViewContentModeScaleAspectFit;  90     [_scrV addSubview:_imgVCenter];  91       92     //图片视图；右边  93     _imgVRight = [[UIImageView alloc] initWithFrame:CGRectMake(kWidthOfScreen * 2.0, 0.0, kWidthOfScreen, kHeightOfScreen)];  94     _imgVRight.contentMode = UIViewContentModeScaleAspectFit;  95     [_scrV addSubview:_imgVRight];  96 }  97   98 - (void)addPageControl {  99     _pageC = [UIPageControl new]; 100     CGSize size= [_pageC sizeForNumberOfPages:_imageCount]; //根据页数返回 UIPageControl 合适的大小 101     _pageC.bounds = CGRectMake(0.0, 0.0, size.width, size.height); 102     _pageC.center = CGPointMake(kWidthOfScreen / 2.0, kHeightOfScreen - 80.0); 103     _pageC.numberOfPages = _imageCount; 104     _pageC.pageIndicatorTintColor = [UIColor whiteColor]; 105     _pageC.currentPageIndicatorTintColor = [UIColor brownColor]; 106     _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 107     [self.view addSubview:_pageC]; 108 } 109  110 - (void)addLabel { 111     _lblImageDesc = [[UILabel alloc] initWithFrame:CGRectMake(0.0, 40.0, kWidthOfScreen, 40.0)]; 112     _lblImageDesc.textAlignment = NSTextAlignmentCenter; 113     _lblImageDesc.textColor = [UIColor whiteColor]; 114     _lblImageDesc.font = [UIFont boldSystemFontOfSize:[UIFont labelFontSize]]; 115     _lblImageDesc.text = @"Fucking now."; 116     [self.view addSubview:_lblImageDesc]; 117 } 118  119 - (void)setInfoByCurrentImageIndex:(NSUInteger)currentImageIndex { 120     NSString *currentImageNamed = [NSString stringWithFormat:@"%lu.png", (unsigned long)currentImageIndex]; 121     _imgVCenter.image = [UIImage imageNamed:currentImageNamed]; 122     _imgVLeft.image = [UIImage imageNamed:[NSString stringWithFormat:@"%lu.png", (unsigned long)((_currentImageIndex - 1 + _imageCount) % _imageCount)]]; 123     _imgVRight.image = [UIImage imageNamed:[NSString stringWithFormat:@"%lu.png", (unsigned long)((_currentImageIndex + 1) % _imageCount)]]; 124      125     _pageC.currentPage = currentImageIndex; 126     _lblImageDesc.text = _mDicImageData[currentImageNamed]; 127 } 128  129 - (void)setDefaultInfo { 130     _currentImageIndex = 0; 131     [self setInfoByCurrentImageIndex:_currentImageIndex]; 132 } 133  134 - (void)reloadImage { 135     CGPoint contentOffset = [_scrV contentOffset]; 136     if (contentOffset.x > kWidthOfScreen) { //向左滑动 137         _currentImageIndex = (_currentImageIndex + 1) % _imageCount; 138     } else if (contentOffset.x < kWidthOfScreen) { //向右滑动 139         _currentImageIndex = (_currentImageIndex - 1 + _imageCount) % _imageCount; 140     } 141      142     [self setInfoByCurrentImageIndex:_currentImageIndex]; 143 } 144  145 - (void)layoutUI { 146     self.view.backgroundColor = [UIColor blackColor]; 147      148     [self loadImageData]; 149     [self addScrollView]; 150     [self addImageViewsToScrollView]; 151     [self addPageControl]; 152     [self addLabel]; 153     [self setDefaultInfo]; 154 } 155  156 #pragma mark - UIScrollViewDelegate 157 - (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView { 158     [self reloadImage]; 159      160     _scrV.contentOffset = CGPointMake(kWidthOfScreen, 0.0); 161     _pageC.currentPage = _currentImageIndex; 162      163     NSString *currentImageNamed = [NSString stringWithFormat:@"%lu.png", (unsigned long)_currentImageIndex]; 164     _lblImageDesc.text = _mDicImageData[currentImageNamed]; 165 } 166  167 @end

ImageInfo.plist

 1 <?xml version="1.0" encoding="UTF-8"?>  2 <!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">  3 <plist version="1.0">  4 <dict>  5     <key>0.png</key>  6     <string>WATCH，它，终于来了。</string>  7     <key>1.png</key>  8     <string>iPhone 6，无双，有此一双。</string>  9     <key>2.png</key> 10     <string>MacBook，轻于时代，先于时代。</string> 11     <key>3.png</key> 12     <string>iPad Air 2，轻轻地，改变一切。</string> 13     <key>4.png</key> 14     <string>iOS 9，它，将要到来。</string> 15 </dict> 16 </plist>