UIPageViewController 索引无法正常工作

Question

基本上，我正在制作一个页面应用程序，它使用UIPageViewController。当用户滚动页面时，他们可以看到不同的内容。现在的问题是，当我滚动页面时，第一页和第二页工作正常，索引正确。但是当我滚动到第三页时，索引保持在"1"，之后不会更改。另一页保持第二页的外观，其索引为"1"。

我正在按照教程进行操作：http://www.appcoda.com/uipageviewcontroller-storyboard-tutorial/

我的代码：

视图控制器.h

#import <UIKit/UIKit.h>
#import "PageContentViewController.h"
#import "PageViewController.h"
@interface ViewController : UIViewController<UIPageViewControllerDataSource, UIPageViewControllerDelegate>
@property (strong, nonatomic) PageViewController *pageViewController;
@property (strong, nonatomic) NSArray *pageTitles;

@end

视图控制器.m：

#import "ViewController.h"
@interface ViewController ()
@end
@implementation ViewController
- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    self.pageTitles = @[@"First Page", @"Second Page", @"Third Page"];
    self.pageViewController = [self.storyboard instantiateViewControllerWithIdentifier:@"PageViewController"];
    self.pageViewController.dataSource = self;
    if ([self.pageTitles count])
    {
        PageContentViewController *startingViewController = [self viewControllerAtIndex: 0];
        NSArray *viewControllers = @[startingViewController];
        [self.pageViewController setViewControllers:viewControllers direction:UIPageViewControllerNavigationDirectionForward animated:NO completion:nil];
        self.pageViewController.view.frame = CGRectMake(0, 0, self.view.frame.size.width, self.view.frame.size.height);
        [self addChildViewController:self.pageViewController];
        [self.view addSubview:self.pageViewController.view];
        [self.pageViewController didMoveToParentViewController:self];
    }
}
- (PageContentViewController *) viewControllerAtIndex: (NSUInteger)index{
    if (index < [self.pageTitles count])
    {
        PageContentViewController *pageContentViewController = [self.storyboard instantiateViewControllerWithIdentifier:@"PageContentViewController"];
        pageContentViewController.titleText = self.pageTitles[index];
        NSLog(@"%li", index);
        UIColor *backgroundColor;
        switch (index) {
            case 0:
                backgroundColor = [UIColor greenColor];
                break;
            case 1:
                backgroundColor = [UIColor blueColor];
                break;
            case 2:
                backgroundColor = [UIColor purpleColor];
                break;
            default:
                break;
        }
        pageContentViewController.backgroundColor = backgroundColor;
        return pageContentViewController;
    }
    return nil;
}
- (UIViewController *)pageViewController:(UIPageViewController *)pageViewController viewControllerAfterViewController:(UIViewController *)viewController
{
    NSUInteger index = ((PageContentViewController *)viewController).pageIndex;

    if (index == NSNotFound)
    {
        return nil;
    }
    index++;
    if (index == [self.pageTitles count])
    {
        return nil;
    }
    return [self viewControllerAtIndex:index];
}
- (UIViewController *)pageViewController:(UIPageViewController *)pageViewController viewControllerBeforeViewController:(UIViewController *)viewController
{
    NSUInteger index = ((PageContentViewController *)viewController).pageIndex;
    if (index == 0 || index == NSNotFound)
    {
        return nil;
    }
    index--;
    return [self viewControllerAtIndex:index];
}
- (NSInteger) presentationCountForPageViewController:(UIPageViewController *)pageViewController
{
    return [self.pageTitles count];
}
- (NSInteger) presentationIndexForPageViewController:(UIPageViewController *)pageViewController
{
    return 0;
}
- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}
@end

页面内容视图控制器.h

#import <UIKit/UIKit.h>
@interface PageContentViewController : UIViewController
@property (weak, nonatomic) IBOutlet UIView *backgroundView;
@property (weak, nonatomic) IBOutlet UILabel *titleLable;
@property (nonatomic) NSUInteger pageIndex;
@property (strong, nonatomic) NSString *titleText;
@property (strong, nonatomic) UIColor *backgroundColor;
@end

页面内容视图控制器.m

#import "PageContentViewController.h"
@interface PageContentViewController ()
@end
@implementation PageContentViewController
- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view.
    self.titleLable.text = self.titleText;
    [self.backgroundView setBackgroundColor:self.backgroundColor];
}
- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}
/*
#pragma mark - Navigation
// In a storyboard-based application, you will often want to do a little preparation before navigation
- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender {
    // Get the new view controller using [segue destinationViewController].
    // Pass the selected object to the new view controller.
}
*/
@end

Answer 1

在 viewControllerAtIndex: 中，你需要设置pageContentViewController的pageIndex属性的值：

pageContentViewController.pageIndex = index;