UIPageControl + UIScrollView 创建一个页面指示器控件

    UIPageControl 类提供了一行点来指示当前显示的是多页面视图的哪一页。点击当前颜色鲜艳的页面指示器的左边或右边，会触发 UIControlEventValueChanged 事件，

并启动设置为控件动作的任何方法。你可以通过调用currentPage 查询控件的新值，并通过调整 numberOfPage 属性设置可用的页面数。

代码 ：使用UIPageControl 指示器

#define BARBUTTON(TITLE, SELECTOR)     [[[UIBarButtonItem alloc] initWithTitle:TITLE style:UIBarButtonItemStylePlain target:self action:SELECTOR] autorelease]
#define RSTRING(X) NSStringFromCGRect(X)

#define BASEHEIGHT    284.0f
#define NPAGES        3

- (void) pageTurn: (UIPageControl *) aPageControl
{
    int whichPage = aPageControl.currentPage;
    [UIView beginAnimations:nil context:NULL];
    [UIView setAnimationDuration:0.3f];
    [UIView setAnimationCurve:UIViewAnimationCurveEaseInOut];
    sv.contentOffset = CGPointMake(320.0f * whichPage, 0.0f);
    [UIView commitAnimations];
}

- (void) scrollViewDidScroll: (UIScrollView *) aScrollView
{
    CGPoint offset = aScrollView.contentOffset;
    pageControl.currentPage = offset.x / 320.0f;
}

- (void) viewDidLoad
{
    self.navigationController.navigationBar.tintColor = COOKBOOK_PURPLE_COLOR;
    self.title = @"Image Scroller";
    
    // Create the scroll view and set its content size and delegate
    sv = [[[UIScrollView alloc] initWithFrame:CGRectMake(0.0f, 0.0f, 320.0f, BASEHEIGHT)] autorelease];
    sv.contentSize = CGSizeMake(NPAGES * 320.0f, sv.frame.size.height);
    sv.pagingEnabled = YES;
    sv.delegate = self;
    
    int i = 0;
    // Load in all the pages
    for ( i;i < NPAGES; i++)
    {
        NSString *filename = [NSString stringWithFormat:@"image%d.png", i+1];
        UIImageView *iv = [[UIImageView alloc] initWithImage:[UIImage imageNamed:filename]];
        iv.frame = CGRectMake(i * 320.0f, 0.0f, 320.0f, BASEHEIGHT);
        [sv addSubview:iv];
        [iv release];
    }
    
    [self.view addSubview:sv];
    
    pageControl.numberOfPages = 3;
    pageControl.currentPage = 0;
    [pageControl addTarget:self action:@selector(pageTurn:) forControlEvents:UIControlEventValueChanged];
}