PageViewController委托函数调用两次

Question

我正在使用UIPageViewController,为我的应用程序进行产品导览.

我按照这个链接http://www.appcoda.com/uipageviewcontroller-tutorial-intro/

我正在做的是根据我获得的索引值在滑动时更改我的"根VC"的背景颜色的简单任务,但是由于委托函数被调用两次,我的索引值不正确,因此,我不是能够做对,下面是我的代码

#import "APPViewController.h"
#import "APPChildViewController.h"

@interface APPViewController ()

@end

@implementation APPViewController

- (void)viewDidLoad {

    [super viewDidLoad];

    self.pageController = [[UIPageViewController alloc] initWithTransitionStyle:UIPageViewControllerTransitionStyleScroll navigationOrientation:UIPageViewControllerNavigationOrientationHorizontal options:nil];

    self.pageController.dataSource = self;
    [[self.pageController view] setFrame:CGRectMake(0, 0, 320, 500)];

    APPChildViewController *initialViewController = [self viewControllerAtIndex:0];

    NSArray *viewControllers = [NSArray arrayWithObject:initialViewController];

    [self.pageController setViewControllers:viewControllers direction:UIPageViewControllerNavigationDirectionForward animated:NO completion:nil];

    [self addChildViewController:self.pageController];
    [[self view] addSubview:[self.pageController view]];
    [self.pageController didMoveToParentViewController:self];

}

- (void)didReceiveMemoryWarning {

    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.

}

- (APPChildViewController *)viewControllerAtIndex:(NSUInteger)index {

    APPChildViewController *childViewController = [[APPChildViewController alloc] initWithNibName:@"APPChildViewController" bundle:nil];
    childViewController.index = index;
    childViewController.view.backgroundColor = [UIColor clearColor];

    if(index == 0)
    {
          self.view.backgroundColor = [UIColor redColor];
     }

    if(index == 1)
    {
          self.view.backgroundColor = [UIColor blueColor];
     }

    if(index == 2)
    {
          self.view.backgroundColor = [UIColor greenColor];
     }


    return childViewController;

}

- (UIViewController *)pageViewController:(UIPageViewController *)pageViewController viewControllerBeforeViewController:(UIViewController *)viewController {

    NSUInteger index = [(APPChildViewController *)viewController index];

    if (index == 0) {
        return nil;
    }

    // Decrease the index by 1 to return
    index--;

   return [self viewControllerAtIndex:index];

}

- (UIViewController *)pageViewController:(UIPageViewController *)pageViewController viewControllerAfterViewController:(UIViewController *)viewController {

    NSUInteger index = [(APPChildViewController *)viewController index];

    index++;

    if (index == 3) {
        return nil;
    }

   return [self viewControllerAtIndex:index];

}

- (NSInteger)presentationCountForPageViewController:(UIPageViewController *)pageViewController {
    // The number of items reflected in the page indicator.
    return 3;
}

- (NSInteger)presentationIndexForPageViewController:(UIPageViewController *)pageViewController {
    // The selected item reflected in the page indicator.
    return 0;
}

请帮助我,我没有得到我错的地方

问候Ranjit

Answer 1

寻找了很多.

我收到了:

- (UIViewController *)pageViewController:(UIPageViewController *)pageViewController viewControllerBeforeViewController:(UIViewController *)viewController;
- (UIViewController *)pageViewController:(UIPageViewController *)pageViewController viewControllerAfterViewController:(UIViewController *)viewController;

2个函数用于获取当前pageViewController后面或前面的pageViewController.

我认为获取当前的pageViewController很困难

我的建议:

在UIPageViewControllerDelegate中,它有一个函数:

 - (void)pageViewController:(UIPageViewController *)pageViewController willTransitionToViewControllers:(NSArray *)pendingViewControllers;

这个函数给你一个pendingViewControllers数组和这个当前的pageViewController数组.所以你可以这样实现:

- (void)pageViewController:(UIPageViewController *)pageViewController willTransitionToViewControllers:(NSArray *)pendingViewControllers
{


if([pendingViewControllers count]>0)
  {
     NSUInteger index =[(APPChildViewController*)[pendingViewControllers objectAtIndex:0] index];

    if(index == 0)
    {
        self.view.backgroundColor = [UIColor redColor];
    }

    if(index == 1)
    {
        self.view.backgroundColor = [UIColor blueColor];
    }

    if(index == 2)
    {
        self.view.backgroundColor = [UIColor greenColor];
    }


  }
}

在viewDidLoad中,添加:

    self.pageController.delegate = self;

    self.view.backgroundColor = [UIColor redColor]; //set first background.

在'APPViewController.h'中你肯定会添加:

@interface APPViewController : UIViewController<UIPageViewControllerDataSource,UIPageViewControllerDelegate>

记住:删除此代码(在'viewControllerAtIndex'函数中)

if(index == 1)
{
    self.view.backgroundColor = [UIColor redColor];
}

if(index == 2)
{
    self.view.backgroundColor = [UIColor blueColor];
}

if(index == 3)
{
    self.view.backgroundColor = [UIColor greenColor];
}

如果您有任何疑问,请告诉我.