1 #import "ViewController.h" 2 #define kDeviceWidth [UIScreen mainScreen].bounds.size.width 3 #define kDeviceHeight [UIScreen mainScreen].bounds.size.height 4 #define Kpage 3 5 @interface ViewController ()<UIScrollViewDelegate> 6 7 @property(nonatomic,strong)UIPageControl *pageCtrl; 8 @property (nonatomic,weak) UIScrollView *scrollView; 9 @property (nonatomic,weak) UIImageView *currentImageView; // 当前imageView 10 @property (nonatomic,weak) UIImageView *nextImageView; // 下一个imageView 11 @property (nonatomic,weak) UIImageView *preImageView; //上一个imageView 12 @property (nonatomic,assign) BOOL isDragging; // 是否正在滚动 13 @property (nonatomic,strong)NSTimer *timer; 14 @end 15 16 @implementation ViewController 17 18 - (void)viewDidLoad { 19 [super viewDidLoad];
// 注意，在有导航栏的情况下，需要在viewDidLoad 中加上 self.automaticallyAdjustsScrollViewInsets = NO;不然会出现图片下移64的情况 ，scrollView.frame的高度要比图片的高度大64，不然，图片显示不全
20 UIScrollView *scrollView =[[UIScrollView alloc] init]; 21 scrollView.frame = CGRectMake(0, 0, kDeviceWidth, kDeviceHeight); 22 [self.view addSubview:scrollView]; 23 self.scrollView = scrollView; 24 [self.scrollView setContentSize:CGSizeMake(kDeviceWidth * 3, kDeviceWidth)]; 25 // 设置隐藏横向条 26 self.scrollView.showsHorizontalScrollIndicator = NO; 27 // 设置自动分页 28 self.scrollView.pagingEnabled = YES; 29 // 设置代理 30 self.scrollView.delegate = self; 31 // 设置当前点 32 self.scrollView.contentOffset = CGPointMake(kDeviceWidth, 0); 33 // 设置是否有边界 34 self.scrollView.bounces = NO;
35 // 初始化当前视图
// 注意：这里如果图片向左轮播，无需初始化上一个视图；如果图片向右轮播，无需初始化下一个视图
36 UIImageView *currentImageView =[[UIImageView alloc] init]; 37 currentImageView.image = [UIImage imageNamed:@"bg_01"]; 38 [self.scrollView addSubview:currentImageView]; 39 self.currentImageView = currentImageView; 40 self.currentImageView.frame = CGRectMake(kDeviceWidth, 0, kDeviceWidth, kDeviceHeight); 41 self.currentImageView.contentMode = UIViewContentModeScaleAspectFill; 42 // 初始化下一个视图 43 UIImageView *nextImageView = [[UIImageView alloc] init]; 44 nextImageView.image = [UIImage imageNamed:@"bg_02"]; 45 [self.scrollView addSubview:nextImageView]; 46 self.nextImageView = nextImageView; 47 self.nextImageView.frame = CGRectMake(kDeviceWidth * 2, 0, kDeviceWidth, kDeviceHeight); 48 self.nextImageView.contentMode = UIViewContentModeScaleAspectFill; 49 // 初始化上一个视图， 50 UIImageView *preImageView =[[UIImageView alloc] init]; 51 preImageView.image = [UIImage imageNamed:@"bg_03"]; 52 preImageView.frame = CGRectMake(0, 0, kDeviceWidth, kDeviceHeight); 53 [self.scrollView addSubview:preImageView]; 54 self.preImageView = preImageView; 55 self.preImageView.contentMode =UIViewContentModeScaleAspectFill; 56 57 // 设置时钟动画 定时器 58 59 self.timer = [NSTimer scheduledTimerWithTimeInterval:2 target:self selector:@selector(update:) userInfo:nil repeats:YES]; 60 // 将定时器添加到主线程 61 [[NSRunLoop mainRunLoop] addTimer:self.timer forMode:NSRunLoopCommonModes]; 62 63 } 64 // 分页 65 -(UIPageControl *)pageCtrl{ 66 if (_pageCtrl == nil) { 67 68 //分页控件 69 _pageCtrl = [[UIPageControl alloc]init]; 70 _pageCtrl.numberOfPages = Kpage; 71 72 CGSize size = [_pageCtrl sizeForNumberOfPages:Kpage]; 73 _pageCtrl.bounds = CGRectMake(0, 0, size.width, size.height); 74 _pageCtrl.center = CGPointMake(self.view.center.x, CGRectGetMaxY(self.scrollView.frame) - 20); 75 _pageCtrl.pageIndicatorTintColor = [UIColor redColor]; 76 _pageCtrl.currentPageIndicatorTintColor = [UIColor greenColor]; 77 78 [self.view addSubview:_pageCtrl]; 79 80 81 } 82 return _pageCtrl; 83 } 84 85 86 -(void)updateTimer{ 87 //修改页号 88 int page = (self.pageCtrl.currentPage + 1 ) % Kpage; 89 self.pageCtrl.currentPage = page; 90 91 } 92 93 94 - (void)update:(NSTimer *)timer{ 95 //定时移动 96 97 if (_isDragging == YES) { 98 99 return ; 100 } 101 CGPoint offSet = self.scrollView.contentOffset; 102 offSet.x +=offSet.x; 103 104 [self updateTimer]; 105 106 [self.scrollView setContentOffset:offSet animated:YES]; 107 if (offSet.x >= kDeviceWidth *2) { 108 offSet.x = kDeviceWidth; 109 } 110 111 } 112 #pragma mark - UIScrollViewDelegate 113 - (void)scrollViewWillBeginDragging:(UIScrollView *)scrollView 114 { 115 _isDragging = YES; 116 } 117 // 停止滚动 118 - (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView 119 { 120 _isDragging = NO; 121 122 } 123 124 // 开始滚动 125 - (void) scrollViewDidScroll:(UIScrollView *)scrollView{ 126 static int i =1; // 当前展示的是第几张图片 127 float offset = self.scrollView.contentOffset.x;
// 注意：这里如果图片向左轮播，无需加载上一个视图；如果图片向右轮播，无需加载下一个视图
128 if (self.nextImageView.image == nil || self.preImageView.image == nil) { 129 // 加载下一个视图 130 NSString *imageName1 = [NSString stringWithFormat:@"bg_0%d",i == Kpage ? 1:i +1]; 131 _nextImageView.image = [UIImage imageNamed:imageName1]; 132 // 加载上一个视图 133 NSString *imageName2 = [NSString stringWithFormat:@"bg_0%d",i==1 ? Kpage :i-1]; 134 _preImageView.image = [UIImage imageNamed:imageName2]; 135 136 }
// 注意：这里如果图片向左轮播，无需if(offset ==0)判断；如果图片向右轮播，无需if (offset == scrollView.bounds.size.width * 2)判断
137 if(offset ==0){ 138 _currentImageView.image = _preImageView.image; 139 scrollView.contentOffset = CGPointMake(scrollView.bounds.size.width, 0); 140 _preImageView.image = nil; 141 if (i == 1) { 142 i =Kpage; 143 } else{ 144 i-=1; 145 } 146 147 } 148 if (offset == scrollView.bounds.size.width * 2) { 149 _currentImageView.image = _nextImageView.image; 150 scrollView.contentOffset = CGPointMake(scrollView.bounds.size.width, 0); 151 _nextImageView.image = nil; 152 if (i == Kpage) { 153 i = 1 ; 154 }else{ 155 i +=1 ; 156 } 157 158 } 159 160 } 161 162 163 @end
假如图片为img1,img2,img3
//具体说明一下：以三张图片向左轮播为例，首先当前页面（就是看的见得）为current位置为320（以5S为例吧，宽度为320）图片为img1，下一张图片next位置为640,图片为img2，
（ i= 1）
1.当前图片2秒后（假如定时器2秒执行一次）移动到640（定时器每执行一次移动一个屏幕宽度）；进入if (offset == scrollView.bounds.size.width * 2) 判断
2.判断结果为当前页面的图片换成前面next的图片，结果为img2，next的图片为空,current当前页面位置变成320（i= 2）
3.因为next的图片为空，所以进入if (self.nextImageView.image == nil || self.preImageView.image == nil)
4.判断结果，根据后面的三目运算next的图片换成img3（因为三目运算）
5.当前图片2秒后又（定时器2秒执行一次）又移动到640（定时器每执行一次移动一个屏幕宽度）；进入if (offset == scrollView.bounds.size.width * 2) 判断把图片换成img3,让next为空，从此无限循环