PageViewController delegate functions called twice

Question

I am working with UIPageViewController , to make a product tour for my application.

I followed this link http://www.appcoda.com/uipageviewcontroller-tutorial-intro/<

Answer 1

Replace these two methods and compile,

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

    NSUInteger index = [(APPChildViewController *)viewController index];
    if (index == 0)
    {
        self. view.backgroundColor = [UIColor redColor];
        return nil;
    }

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

    if(index == 2)
    {
        self.view.backgroundColor = [UIColor greenColor];
    }
    if(index == 3)
    {
        self.view.backgroundColor = [UIColor brownColor];
    }
    /*if(index == 4)
    {
        self.view.backgroundColor = [UIColor whiteColor];
    }*/

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

    return [self viewControllerAtIndex:index];

}

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

    NSUInteger index = [(APPChildViewController *)viewController 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];
    }
    if(index == 3)
    {
        self.view.backgroundColor = [UIColor brownColor];
    }
    if(index == 4)
    {
        self.view.backgroundColor = [UIColor whiteColor];
        return nil;
    }

    /*if (index == 5) {
        return nil;
    }*/
    index++;

    return [self viewControllerAtIndex:index];

}

and add this in the end of - (void)viewDidLoad {

self.view.backgroundColor = [UIColor redColor];