iOS源码之OC相册，可以循环查看图片

#import "ViewController.h"
#import "YZUIScrollView.h"
#define kuan ([UIScreen mainScreen].bounds.size.width+20)
#define gao [UIScreen mainScreen].bounds.size.height
@interface ViewController ()<UIScrollViewDelegate>
@property (weak, nonatomic) IBOutlet UIScrollView *huaBu;
@property(nonatomic,strong)NSArray *images;
@property(nonatomic)NSInteger currentIndex;
@end

@implementation ViewController
//懒加载,调用get方法时对属性进行初始化
-(NSArray *)images
{
    if(_images==nil)
    {
        NSMutableArray *imagearray=[NSMutableArray array];
        for (int i=1; i<7; i++) {
            NSString *imageName=[NSString stringWithFormat:@"new_feature_%d",i];
            UIImage *image=[UIImage imageNamed:imageName];
            [imagearray addObject:image];
        }
        _images=imagearray;
    }
    return _images;
}
- (void)viewDidLoad {
    [super viewDidLoad];
    //设置UIScrollView的contentSize
    _huaBu.contentSize=CGSizeMake(kuan*3, gao);
    //设置分页
    _huaBu.pagingEnabled=YES;
    //隐藏水平滚动栏和垂直滚动栏
    _huaBu.showsHorizontalScrollIndicator=NO;
    _huaBu.showsVerticalScrollIndicator=NO;
    //设置背景颜色,突出不同的图片
    _huaBu.backgroundColor=[UIColor blackColor];
    //设置代理要遵守协议<UIScrollViewDelegate>
    _huaBu.delegate=self;
    //调用方法添加子视图
    [self tianJiaZiShiTu];
    //调用方法添加图片
    [self tianJiaTuPian];
}
//添加子视图的方法
-(void)tianJiaZiShiTu
{
    //相册的话，是一个大的UIScrollView中放了很多的小UIScrollView，但是为了节省内存空间，所以只是添加了三个UIScrollView（图片不停的变换位置）
    for (int i=0; i<3; i++) {
        //创建YZUIScrollView
        YZUIScrollView * yzuisv=[[YZUIScrollView alloc] initWithFrame:CGRectMake(kuan*i, 0, kuan-20, gao)];
        //添加YZUIScrollView
        [_huaBu addSubview:yzuisv];
        //设置tag值，便于区分
        yzuisv.tag=1000+i;
    }
}
//添加方法的图片
-(void)tianJiaTuPian
{
    YZUIScrollView *leftSC=(YZUIScrollView *)[_huaBu viewWithTag:1000];
    YZUIScrollView *middleSC=(YZUIScrollView *)[_huaBu viewWithTag:1001];
    YZUIScrollView *rightSC=(YZUIScrollView *)[_huaBu viewWithTag:1002];
    leftSC.image=self.images[[self indexFofEnable:_currentIndex-1]];
    middleSC.image=self.images[[self indexFofEnable:_currentIndex]];
    rightSC.image=self.images[[self indexFofEnable:_currentIndex+1]];
    //设置偏移量，这步很重要
    _huaBu.contentOffset=CGPointMake(kuan, 0);
}
//确保索引可用
-(NSInteger)indexFofEnable:(NSInteger)index
{
    if(index<0)
    {
        return self.images.count-1;
    }
    else if (index>self.images.count-1)
    {
        return 0;
    }
    else
        return index;
}
//滚动结束后，把所有的缩放视图比例还原为1.0
-(void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView
{
    for (id obj in _huaBu.subviews) {
        if([obj isKindOfClass:[UIScrollView class]])
        {
            UIScrollView *scaleSC=(UIScrollView *)obj;
            scaleSC.zoomScale=1.0;
        }
    }
    //判断左右滑动
    //偏移量的x为0，就是说明向右滑动了，就是看的之前左边的那张图片
    if(scrollView.contentOffset.x==0)
    {
        //对应的图像应该是变成左边的图像
        _currentIndex--;
    }
    //偏移量的x为两个屏幕的宽，就是说明向左滑动了，就是看的之前右边的那张图片
    else if(scrollView.contentOffset.x== kuan*2)
    {
        //对应的图像应该是变成右边的图像
        _currentIndex++;
    }
    _currentIndex=[self indexFofEnable:_currentIndex];
    [self tianJiaTuPian];
}
- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

@end

　　第二个类

#import "YZUIScrollView.h"


@interface YZUIScrollView ()<UIScrollViewDelegate>

@property(nonatomic,strong)UIImage *image;//内容视图的图片

@property(nonatomic,strong)UIImageView *imageview;
@end

@implementation YZUIScrollView

-(instancetype)initWithFrame:(CGRect)frame
{
    if(self =[super initWithFrame:frame])
    {
        //添加内容视图
        UIImageView *imageview1=[[UIImageView alloc] initWithFrame:self.bounds];
        [self addSubview:imageview1];
        _imageview=imageview1;
        //设置最大最小倍数和代理
        self.minimumZoomScale=0.5;
        self.maximumZoomScale=1.5;
        self.delegate=self;
        //双击事件
        UITapGestureRecognizer *tap=[[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(shuangJi:)];
        tap.numberOfTapsRequired=2;
        [self addGestureRecognizer:tap];
    }
    return self;
}
-(void)shuangJi:(UITapGestureRecognizer *)tap
{
    //当缩放比例不为1.0，还原缩放比例
    if (self.zoomScale !=1.0) {
        [self setZoomScale:1.0 animated:YES];
        return ;
    }
    CGPoint location =[tap locationInView:self];
    CGRect rect =CGRectMake(location.x-100, location.y-100,200,200);
    [self zoomToRect:rect animated:YES];
}
//重写setImg方法
-(void)setImage:(UIImage *)image
{
    //set本身的方法要完成的事必须完成
    _image=image;
    //设置内容视图的图片
    _imageview.image=image;
}
//UIScrollViewDelegate代理方法
-(UIView *)viewForZoomingInScrollView:(UIScrollView *)scrollView
{
    return _imageview;
}
@end