how to add two view controllers in UIPageViewcontroller - ios

Question

I m using UIPageViewController on iPad where I need to show a firstviewController in the first page and ContentViewController in the next page in landscape.
If I set the NSArray with two viewControllers the app is crashes at [self.pagviewController setViewController:] with the following exception:
The number of provided view controllers (2) doesn't match the number required (1) for the requested spine location (UIPageViewControllerSpineLocationMin)
Below is the code:
#pragma mark - UIPageViewControllerDataSource Methods
- (UIViewController *)pageViewController:(UIPageViewController *)pageViewController
viewControllerBeforeViewController:(UIViewController *)viewController
{
NSUInteger currentIndex = [self.modelArray indexOfObject:[(ContentViewController *)viewController textContents]];
if(currentIndex == 0)
{
return nil;
}
ContentViewController *contentViewController = [[ContentViewController alloc] init];
contentViewController.textContents = [self.modelArray objectAtIndex:currentIndex - 1];
return contentViewController;
}
- (UIViewController *)pageViewController:(UIPageViewController *)pageViewController
viewControllerAfterViewController:(UIViewController *)viewController
{
NSUInteger currentIndex = [self.modelArray indexOfObject:[(ContentViewController *)viewController textContents]];
if(currentIndex == self.modelArray.count-1)
{
return nil;
}
ContentViewController *contentViewController = [[ContentViewController alloc] init];
contentViewController.textContents = [self.modelArray objectAtIndex:currentIndex + 1];
return contentViewController;
}
//#pragma mark - UIPageViewControllerDelegate Methods
- (UIPageViewControllerSpineLocation)pageViewController:(UIPageViewController *)pageViewController
spineLocationForInterfaceOrientation:(UIInterfaceOrientation)orientation
{
if(UIInterfaceOrientationIsPortrait(orientation))
{
//Set the array with only 1 view controller
UIViewController *currentViewController = [self.pageViewController.viewControllers objectAtIndex:0];
NSArray *viewControllers = [NSArray arrayWithObject:currentViewController];
[self.pageViewController setViewControllers:viewControllers direction:UIPageViewControllerNavigationDirectionForward animated:YES completion:NULL];
//Important- Set the doubleSided property to NO.
self.pageViewController.doubleSided = NO;
//Return the spine location
return UIPageViewControllerSpineLocationMin;
}
else
{
NSArray *viewControllers = nil;
ContentViewController *currentViewController = [self.pageViewController.viewControllers objectAtIndex:0];
NSUInteger currentIndex = [self.modelArray indexOfObject:[(ContentViewController *)currentViewController textContents]];
if(currentIndex == 0 || currentIndex %2 == 0)
{
UIViewController *nextViewController = [self pageViewController:self.pageViewController viewControllerAfterViewController:currentViewController];
viewControllers = [NSArray arrayWithObjects:currentViewController, nextViewController, nil];
}
else
{
UIViewController *previousViewController = [self pageViewController:self.pageViewController viewControllerBeforeViewController:currentViewController];
viewControllers = [NSArray arrayWithObjects:previousViewController, currentViewController, nil];
}
//Now, set the viewControllers property of UIPageViewController
[self.pageViewController setViewControllers:viewControllers direction:UIPageViewControllerNavigationDirectionForward animated:YES completion:NULL];
return UIPageViewControllerSpineLocationMid;
}
}
- (void)viewDidLoad
{
[super viewDidLoad];
appDelegate = (AppDelegate *) [[UIApplication sharedApplication] delegate];
//Instantiate the model array
self.modelArray = [[NSMutableArray alloc] init];
self.vcs = [[NSMutableArray alloc]init];
for (int index = 1; index <= 2 ; index++)
{
[self.modelArray addObject:[NSString stringWithFormat:#"Page %d",index]];
}
//Step 1
//Instantiate the UIPageViewController.
self.pageViewController = [[UIPageViewController alloc] initWithTransitionStyle:UIPageViewControllerTransitionStylePageCurl
navigationOrientation:UIPageViewControllerNavigationOrientationHorizontal options:nil];
//Step 2:
//Assign the delegate and datasource as self.
self.pageViewController.delegate = self;
self.pageViewController.dataSource = self;
//Step 3:
//Set the initial view controllers.
appDelegate.contentViewController.textContents = [self.modelArray objectAtIndex:0];
NSArray *viewControllers = [NSArray arrayWithObjects:appDelegate.firstViewController,appDelegate.contentViewController,nil];
[self.pageViewController setViewControllers:viewControllers
direction:UIPageViewControllerNavigationDirectionForward
animated:NO
completion:nil];
//Step 4:
//ViewController containment steps
//Add the pageViewController as the childViewController
[self addChildViewController:self.pageViewController];
//Add the view of the pageViewController to the current view
[self.view addSubview:self.pageViewController.view];
//Call didMoveToParentViewController: of the childViewController, the UIPageViewController instance in our case.
[self.pageViewController didMoveToParentViewController:self];
//Step 5:
// set the pageViewController's frame as an inset rect.
CGRect pageViewRect = self.view.bounds;
pageViewRect = CGRectInset(pageViewRect, 40.0, 40.0);
self.pageViewController.view.frame = pageViewRect;
//Step 6:
//Assign the gestureRecognizers property of our pageViewController to our view's gestureRecognizers property.
self.view.gestureRecognizers = self.pageViewController.gestureRecognizers;
}

Answer 1

The problem is you passing an array containing two view controllers to the page view controller while it expects one at a time, change your array to be like this :
NSArray *viewControllers = #[appDelegate.firstViewController];
You will pass one of the views but viewControllerAfterViewController and viewControllerBeforeViewController will handle the rest.

Answer 2

Ah..Finally got solution for this same issue.., it may helps you..
When we set the spine location to UIPageViewControllerSpineLocationMid, the doubleSided property of the pageViewController is automatically set to YES. This means that the content on page front will not partially show through back. But when this property is set to NO, the content on page front will partially show through back, giving the page a translucent kind of effect. So, in the portrait orientation, we have to set the value to NO, otherwise it would result in an exception.
So in your UIPageviewcontroller delegate method, in else part add this doubleSided property as YES when you return spineLocation as UIPageViewControllerSpineLocationMid
self.pageViewController.doubleSided = YES;
return UIPageViewControllerSpineLocationMid;

Answer 3

self.pageViewController.doubleSided = NO;
return UIPageViewControllerSpineLocationMid;
This is the solution for the exception.
In xcode it self you could find this.
Go to the UIPageViewcontroller class there you could see the explanation for this like:
#property (nonatomic, readonly) UIPageViewControllerSpineLocation spineLocation; // If transition style is 'UIPageViewControllerTransitionStylePageCurl', default is 'UIPageViewControllerSpineLocationMin', otherwise 'UIPageViewControllerSpineLocationNone'.
// Whether client content appears on both sides of each page. If 'NO', content on page front will partially show through back.
// If 'UIPageViewControllerSpineLocationMid' is set, 'doubleSided' is set to 'YES'. Setting 'NO' when spine location is mid results in an exception.
#property (nonatomic, getter=isDoubleSided) BOOL doubleSided; // Default is 'NO'.

Answer 4

Instead of implementing a full data source, you can set the PageViewController with one view controller at a time each time the user pushes a next or back button, like
[pageViewController setViewControllers:#[contentViewController]
direction:UIPageViewControllerNavigationDirectionForward
animated:YES
completion:nil];
This will animate the page transition as you switch.