AJ学IOS（11）UI之图片自动轮播

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先看效果

代码

#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

实现思路

1.scrollView getter方法懒加载
指定了大小，添加到视图

2，viewDidLoad中添加图像，并计算位置

3，运行观察效果，修改scrollView的属性….

4，实例化UIPageControl

5，因为分页控件与滚动视图分离，因此监听滚动停止代理方法，修改分页控件的页数

6，将UIPageControl定义成属性，并且添加监听方法。

7，实现监听方法，页数变化后，修改scrollView的位置

8，添加时钟，调用分页控件的监听方法，实现图片自动轮播