UIPageControl的简单示例

本文只列出核心代码，其他的请参考附件。

 

AppDelegate.h

 

#import <UIKit/UIKit.h>

@interface AppDelegate : NSObject <UIApplicationDelegate, UIScrollViewDelegate> {
	UIWindow *window;
	UIScrollView *scrollView;
	UIPageControl *pageControl;
    NSMutableArray *viewControllers;	
    BOOL pageControlUsed;
}

@property (nonatomic, retain) IBOutlet UIWindow *window;
@property (nonatomic, retain) IBOutlet UIScrollView *scrollView;
@property (nonatomic, retain) IBOutlet UIPageControl *pageControl;
@property (nonatomic, retain) NSMutableArray *viewControllers;

- (IBAction)changePage:(id)sender;

@end

 

AppDelegate.m

 

#import "AppDelegate.h"
#import "MyViewController.h"

static NSUInteger kNumberOfPages = 7;

@interface AppDelegate (PrivateMethods)

- (void)loadScrollViewWithPage:(int)page;
- (void)scrollViewDidScroll:(UIScrollView *)sender;

@end

@implementation AppDelegate

@synthesize window, scrollView, pageControl, viewControllers;

- (void)dealloc {
    [viewControllers release];
    [scrollView release];
    [pageControl release];
    [window release];
    [super dealloc];
}

- (void)applicationDidFinishLaunching:(UIApplication *)application {
    NSMutableArray *controllers = [[NSMutableArray alloc] init];
    for (unsigned i = 0; i < kNumberOfPages; i++) {
        [controllers addObject:[NSNull null]];
    }
    self.viewControllers = controllers;
    [controllers release];

    scrollView.pagingEnabled = YES;
    scrollView.contentSize = CGSizeMake(scrollView.frame.size.width * kNumberOfPages, scrollView.frame.size.height);
    scrollView.showsHorizontalScrollIndicator = NO;
    scrollView.showsVerticalScrollIndicator = NO;
    scrollView.scrollsToTop = NO;
    scrollView.delegate = self;

    pageControl.numberOfPages = kNumberOfPages;
    pageControl.currentPage = 0;

    [self loadScrollViewWithPage:0];
    [self loadScrollViewWithPage:1];
}

- (void)loadScrollViewWithPage:(int)page {
    if (page < 0) return;
    if (page >= kNumberOfPages) return;

    MyViewController *controller = [viewControllers objectAtIndex:page];
    if ((NSNull *)controller == [NSNull null]) {
        controller = [[MyViewController alloc] initWithPageNumber:page];
        [viewControllers replaceObjectAtIndex:page withObject:controller];
        [controller release];
    }

    if (nil == controller.view.superview) {
        CGRect frame = scrollView.frame;
        frame.origin.x = frame.size.width * page;
        frame.origin.y = 0;
        controller.view.frame = frame;
        [scrollView addSubview:controller.view];
    }
}

- (void)scrollViewDidScroll:(UIScrollView *)sender {
    if (pageControlUsed) {
        return;
    }
	
    CGFloat pageWidth = scrollView.frame.size.width;
    int page = floor((scrollView.contentOffset.x - pageWidth / 2) / pageWidth) + 1;
    pageControl.currentPage = page;

    [self loadScrollViewWithPage:page - 1];
    [self loadScrollViewWithPage:page];
    [self loadScrollViewWithPage:page + 1];
}

- (void)scrollViewWillBeginDragging:(UIScrollView *)scrollView {
    pageControlUsed = NO;
}

- (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView {
    pageControlUsed = NO;
}

- (IBAction)changePage:(id)sender {
    int page = pageControl.currentPage;
	
    [self loadScrollViewWithPage:page - 1];
    [self loadScrollViewWithPage:page];
    [self loadScrollViewWithPage:page + 1];
    
    CGRect frame = scrollView.frame;
    frame.origin.x = frame.size.width * page;
    frame.origin.y = 0;
    [scrollView scrollRectToVisible:frame animated:YES];
    
    pageControlUsed = YES;
}

@end