关于UIScrollView广告栏的无限循环

虽然基本还是用到第三方，但是写一些简单的广告栏循环的话，还是要会写。知道基本的原理。

本文写一个简单的Demo

因为加载的图片基本都是数据库的图片，所以首先要有SDWebImage，然后添加头文件#import "UIImageView+WebCache.h"
简单的写两个宏
#define UIScreen_width ([UIScreen mainScreen].bounds.size.width)
#define UIScreen_height ([UIScreen mainScreen].bounds.size.height)
添加代理<UIScrollViewDelegate>
然后定义变量

@property (strong, nonatomic) NSMutableArray *imageArray;//存放图片的数组
@property (strong, nonatomic) UIScrollView *ADScroll;//广告栏的底层ScrollView
@property (strong, nonatomic) NSTimer *timer;//计时器

开始在.m中完成简单的Demo

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    _imageArray = [NSMutableArray array];
    [self createAD];
}

-(void)createAD{
    _ADScroll = [[UIScrollView alloc] initWithFrame:CGRectMake(0, 50, UIScreen_width, UIScreen_height/3)];
    _ADScroll.delegate = self;
    [self.view addSubview:_ADScroll];
    [self addImagesToScrollView];//添加图片
    [self createTimer];//创建计时器
}

-(void)addImagesToScrollView{
    //这里随便在网上搜了四张图片存放在图片数组中
    NSArray *arr = @[@"http://www.pptbz.com/pptpic/UploadFiles_6909/201204/2012041411433867.jpg",@"http://pic25.nipic.com/20121112/5955207_224247025000_2.jpg",@"http://img10.3lian.com/c1/newpic/10/08/04.jpg",@"http://img3.imgtn.bdimg.com/it/u=2699593702,2049257415&fm=206&gp=0.jpg"];
    [_imageArray addObjectsFromArray:arr];
    int i = 0;
    for (; i < _imageArray.count; i++) {
        UIImageView *img = [[UIImageView alloc] init];
        img.frame = CGRectMake(UIScreen_width * (i + 1), 50, UIScreen_width, UIScreen_height/3);
        [img sd_setImageWithURL:[NSURL URLWithString:arr[i]]];
        img.tag = i;
        [_ADScroll addSubview:img];
        
        img.userInteractionEnabled = YES;
        UITapGestureRecognizer *tap = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(tapClick:)];
        [img addGestureRecognizer:tap];
    }
    // 将最后一张图片弄到第一张的位置
    UIImageView *img = [[UIImageView alloc] initWithFrame:CGRectMake(0, 50, UIScreen_width, UIScreen_height/3)];
    [img sd_setImageWithURL:[NSURL URLWithString:_imageArray[i-1]]];
    [_ADScroll addSubview:img];
    // 将第一张图片放到最后位置，造成视觉上的循环
    UIImageView *img0 = [[UIImageView alloc] initWithFrame:CGRectMake(UIScreen_width * (i + 1), 50, UIScreen_width, UIScreen_height/3)];
    [img0 sd_setImageWithURL:[NSURL URLWithString:_imageArray[0]]];
    [_ADScroll addSubview:img0];
    [_ADScroll setContentOffset:CGPointMake(UIScreen_width, 0)];//将起始位置设置在这里
    
    _ADScroll.pagingEnabled = YES;
    _ADScroll.scrollEnabled = YES;
    
    _ADScroll.showsHorizontalScrollIndicator = NO;
    _ADScroll.showsVerticalScrollIndicator = NO;
    _ADScroll.contentSize = CGSizeMake((i+2)*UIScreen_width, UIScreen_height/3);
}

#pragma mark - 给每一张imageView添加点击事件
-(void)tapClick:(UITapGestureRecognizer *)tap{
    UIImageView *image = (UIImageView *)tap.view;
    int a = (int)image.tag;
    NSLog(@"a = %i ",a);
//    NSLog(@"111111");
    
}

#pragma mark - NSTimer
-(void)createTimer{
    if (!_timer) {
        _timer = [NSTimer timerWithTimeInterval:2.0 target:self selector:@selector(timerRunning) userInfo:nil repeats:YES];
        [[NSRunLoop currentRunLoop] addTimer:_timer forMode:NSRunLoopCommonModes];
    }
}

-(void)timerRunning{
    
    float Offx = _ADScroll.contentOffset.x;
    Offx += UIScreen_width;
    [_ADScroll setContentOffset:CGPointMake(Offx, 0) animated:YES];
}

-(void)scrollViewDidScroll:(UIScrollView *)scrollView{
    if (_ADScroll == scrollView) {
        //往左滑
        if (scrollView.contentOffset.x >= scrollView.contentSize.width - UIScreen_width ) {
            scrollView.contentOffset = CGPointMake(UIScreen_width, 0);
        }
        //往右滑
        if (scrollView.contentOffset.x <= 0) {
            scrollView.contentOffset = CGPointMake(UIScreen_width * _imageArray.count, 0); // 这里的4，是整个Image数组的个数。
        }
//        if (page == 0) {
//            [scrollView setContentOffset:CGPointMake(UIScreen_width * _imageArray.count, 0)];
//
//        }else if (page == _imageArray.count + 1){
//            // 如果是第最后一页就跳转到数组第一个元素的地点
//            [scrollView setContentOffset:CGPointMake(UIScreen_width, 0)];
//        }
    }
}

-(void)dealloc{
    [_imageArray removeAllObjects];
    [_ADScroll removeFromSuperview];
    [_timer invalidate];
    _timer = nil;
}

上边就是一整个完整的Demo，不过是最简单的循环。
如果想要看一些其他的可以看这里——UIScrollView(循环滚动图片)
以及——iOS_UIScrollView实现无限滚动,思路与代码