ios 图片自动轮播

#import "NYViewController.h"

#define kImageCount 5

@interface NYViewController () <UIScrollViewDelegate>
@property (nonatomic, strong) UIScrollView *scrollView;
@property (nonatomic, strong) UIPageControl *pageControl;

@property (nonatomic, strong) NSTimer *timer;
@end

@implementation NYViewController

//懒加载加载scrollView
-(UIScrollView *)scrollView
{
if (_scrollView == nil) {
_scrollView = [[UIScrollView alloc]initWithFrame:CGRectMake(10, 20, 300, 130)];
_scrollView.backgroundColor = [UIColor redColor];

[self.view addSubview:_scrollView];

//contentSize
//高度为0 只水平滚动
self.scrollView.contentSize = CGSizeMake(kImageCount * _scrollView.bounds.size.width, 0);

//取消弹簧效果
_scrollView.bounces = NO;

//取消滚动条
_scrollView.showsHorizontalScrollIndicator = NO;//水平
_scrollView.showsVerticalScrollIndicator = NO;//竖直

//要分页
_scrollView.pagingEnabled = YES;

//设置代理
_scrollView.delegate = self;

}
return _scrollView;
}

-(UIPageControl *)pageControl
{
if (_pageControl == nil) {
//分页控件，本质上和scrollView没有任何关系，是两个独立的控件
_pageControl = [[UIPageControl alloc]init];

//总页数
_pageControl.numberOfPages = kImageCount;
//控件尺寸
CGSize size = [_pageControl sizeForNumberOfPages:kImageCount];

_pageControl.bounds = CGRectMake(0, 0, size.width, size.height);
_pageControl.center = CGPointMake(self.view.center.x, 130);

//设置颜色
_pageControl.pageIndicatorTintColor = [UIColor redColor];
_pageControl.currentPageIndicatorTintColor = [UIColor blackColor];

[self.view addSubview:_pageControl];

//添加监听方法
/**在OC中，绝大多数“继承UIControl控件”，都可以监听UIControlEventValueChanged事件，只有button除外，button是点得，是touchup。。。*/
[_pageControl addTarget:self action:@selector(pageChanged:) forControlEvents:UIControlEventValueChanged];
}
return _pageControl;
}

//分页控件的监听方法
-(void)pageChanged:(UIPageControl *)page
{
//根据页数，调整滚动视图中得图片位置contentOffset
CGFloat x = page.currentPage * self.scrollView.bounds.size.width;
[self.scrollView setContentOffset:CGPointMake(x, 0) animated:YES];
}

- (void)viewDidLoad
{
[super viewDidLoad];

//设置图片
for (int i = 0; i<kImageCount; i++) {
NSString *imageName = [NSString stringWithFormat:@"img_%02d", i+1 ];
UIImage *image = [UIImage imageNamed:imageName];

UIImageView *imageView = [[UIImageView alloc] initWithFrame: self.scrollView.bounds];
imageView.image = image;

[self.scrollView addSubview:imageView];
}

//计算imageView的位置
[self.scrollView.subviews enumerateObjectsUsingBlock:^(UIImageView *imageView, NSUInteger idx, BOOL *stop) {
//调整x =》 origin =》frame
CGRect frame = imageView.frame;
frame.origin.x = idx * frame.size.width;
imageView.frame = frame;

}];

//分页初始页数为0
self.pageControl.currentPage = 0;

//启动时钟
[self startTimer];

}

/**启动时钟*/
-(void)startTimer
{
self.timer = [NSTimer scheduledTimerWithTimeInterval:2.0 target:self selector:@selector(updateTimer) userInfo:nil repeats:YES];

//添加运行循环
[[NSRunLoop currentRunLoop]addTimer:self.timer forMode:NSRunLoopCommonModes];

}

-(void)updateTimer
{
//页号发生变化
//（当前页数 + 1） % 总页数
int page = (self.pageControl.currentPage+1) % kImageCount;
self.pageControl.currentPage = page;
//调用监听方法。让滚动视图滚动
[self pageChanged:self.pageControl];
}

#pragma mark - scrollView的代理方法

//滚动视图停下来
-(void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView
{
// 停下来的当前页数,通过contentOffset获取当前偏移量
NSLog(@"%@",NSStringFromCGPoint(scrollView.contentOffset));

//计算页数
int page = scrollView.contentOffset.x/scrollView.bounds.size.width;

self.pageControl.currentPage = page;

}

/**
抓住图片时，停止时钟，松手后，开启时钟
*/
-(void)scrollViewWillBeginDragging:(UIScrollView *)scrollView
{
//停止时钟，停止后就不能在使用，如果要启用时钟，需要重新实例化
[self.timer invalidate];
}

-(void)scrollViewDidEndDragging:(UIScrollView *)scrollView willDecelerate:(BOOL)decelerate
{
//启动时钟
[self startTimer];

}
@end