PageViewController delegate functions called twice

ios, ios5, ios6, uipageviewcontroller

Solution

After looking for a lot.

I receive that:

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

2 functions use to get pageViewController behind or in front of current pageViewController.

I thinks it's difficult to get current pageViewController

My suggestion:

In UIPageViewControllerDelegate, it have a function :

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

This function to give you a pendingViewControllers array and this's current pageViewController array. So you can implement like that :

- (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];
    }


  }
}

In viewDidLoad, you add :

    self.pageController.delegate = self;

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

In 'APPViewController.h' you sure add:

@interface APPViewController : UIViewController<UIPageViewControllerDataSource,UIPageViewControllerDelegate>

Remember : remove this code (in 'viewControllerAtIndex' function)

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

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

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

Let's me know if you have any questions.

Problem

I am working with UIPageViewController , to make a product tour for my application. I followed this link http://www.appcoda.com/uipageviewcontroller-tutorial-intro/ I am doing is simple task of changing backgound color of my "root VC" on swipe, based on the index value I get, but as the delegate functions are called twice, my index value is not correct and because of that, I am not able to get it right, below is my code ``` #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; } ``` Please help me out, I am not getting where I am going wrong Regards Ranjit

Original source