图片轮播

1 添加图片 

2 设置scrollView的滚动范围 scrollView.contentSize = CGSizeMake(contentW, 0)

3 设置分页 scrollView.pagingEnabled = YES

4 监听scrollView的滚动  scrollView.delegate = self

5 添加计时器

[NSTimer scheduledTimerWithTimeInterval: 2 target:self selector:@selector(nextImage) userInfo: nil repeats:YES];

- (void)nextImage {

    if (self.pageControl.currentPage == 4) {

    self.pageControl.currentPage = 0

 } else  {

   self.pageControl.currentPage++;

}

滚动时计算页码

- (void)scrollViewDidScroll:(UIScrollView *)scrollView {

    CGFloat scrollViewW = scrollView.frame.size.width;

    CGFloat x = scrollView.contentOffset.x;

    int page = (x + scrollViewW / 2) / scrollViewW;

    self.pageControl.currentPage = page;

}

开始拖拽的时候关闭定时器

- (void)scrollVIewWillBeginDragging:(UIScrollView *)scrollView {

      [self.timer removeTimer];

}

停止拖拽时重新添加计时器

- (void)scrollViewDidEndDragging:(UIScrollView *)scrollView {

      [self addTimer];

}

- (void)addTimer {

    self.timer = [NSTimer scheduledTimerWithTimeInterval:1 target: self selector:@selector(nextImage) userInfo:nil  repeats: YES];

[[NSRunLOOP currentRunLoop] addTimer:self.timer forMode:@"NSRunLoopCommonModes"];

}