UIPageControl + UIScrollView 创建一个首尾相连页面指示器控件

  上一篇文章里面已经讲到怎么创建一个页面指示器控件了，今天这篇文章是创建一个首尾相连的页面指示器控件，

代码：

#define BASEHEIGHT    284.0f
#define NPAGES        5 // works better with 5 or more. will work with 3 minimum
#define BIGNUM        500

@interface TestBedViewController : UIViewController <UIScrollViewDelegate>
{
    IBOutlet UIPageControl *pageControl;
    UIScrollView *sv;
    int cpage;
}
@end

@implementation TestBedViewController
- (void) updatePagePlacement
{
    CGPoint offset = sv.contentOffset;

    // Current Page
    UIView *v = [sv viewWithTag:900 + cpage];
    CGRect newframe = CGRectMake(offset.x, 0.0f, 320.0f, BASEHEIGHT);
    if (!CGRectEqualToRect(newframe, v.frame)) v.frame = newframe;
    // printf("Center: %d\n", cpage);
    
    // Pages to the left
    int half = (NPAGES / 2);
    float dx = -320.0f * half;
    int i = 0;
    for ( i;i < half; i++)
    {
        int tag = (cpage + i + NPAGES - half) % NPAGES;
        // printf("Left: %d\n", tag);
        UIView *v = [sv viewWithTag:900 + tag];
        CGRect newframe = CGRectMake(offset.x + dx, 0.0f, 320.0f, BASEHEIGHT);
        if (!CGRectEqualToRect(newframe, v.frame)) v.frame = newframe;
        dx += 320.0f;
    }
    
    // Pages to the right
    int nleft = NPAGES - half;
    dx = 320.0f;
    int ii = 1;
    for (ii ;ii < nleft; ii++)
    {
        int tag = (cpage + ii + NPAGES) % NPAGES;
        // printf("Right: %d\n", tag);
        UIView *v = [sv viewWithTag:900 + tag];
        CGRect newframe = CGRectMake(offset.x + dx, 0.0f, 320.0f, BASEHEIGHT);
        if (!CGRectEqualToRect(newframe, v.frame)) v.frame = newframe;
        dx += 320.0f;
    }
}

- (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView
{
    CGPoint offset = sv.contentOffset;
    int thispage = (int)(offset.x / 320.0f) % NPAGES;
    [self updatePagePlacement];
    cpage = thispage;
}

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

- (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(BIGNUM * 2 * NPAGES * 320.0f, sv.frame.size.height);
    sv.contentOffset = CGPointMake(320.0f * BIGNUM * NPAGES, 0.0f);
    sv.pagingEnabled = YES;
    sv.showsHorizontalScrollIndicator = NO;
    sv.delegate = self;
    
    int i = 0;
    // Load in all the pages
    for ( i;i < NPAGES; i++)
    {
        NSString *filename = [NSString stringWithFormat:@"image%d.png", ((i % 3) +1)];
        UIImageView *iv = [[UIImageView alloc] initWithImage:[UIImage imageNamed:filename]];
        iv.frame = CGRectMake(0.0f, 0.0f, 320.0f, BASEHEIGHT);
        iv.tag = 900 + i;
        [sv addSubview:iv];
        
        UILabel *label = [[UILabel alloc] initWithFrame:CGRectZero];
        label.text = [NSString stringWithFormat:@"Slide %d\n", i + 1];
        label.backgroundColor = [UIColor blackColor];
        label.textColor = [UIColor whiteColor];
        [label sizeToFit];
        label.center = iv.center;
        [iv addSubview:label];
        [label release];
        
        [iv release];
    }
    
    cpage = 0;
    [self updatePagePlacement];
    
    [self.view addSubview:sv];

    pageControl.numberOfPages = NPAGES;
    pageControl.currentPage = 0;
    pageControl.enabled = NO;
}
@end