UIPageViewController doesn't work at all; totally blank

Question

So,

I'm trying to use the UIPageViewController with a custom application workflow, but I'm implementing it exactly as recommended in the docs.

 self.pageViewController = [[[UIPageViewController alloc]  initWithTransitionStyle:UIPageViewControllerTransitionStylePageCurl
                                                            navigationOrientation:UIPageViewControllerNavigationOrientationHorizontal options:nil] autorelease]; 

//calls setViewControllers:direction:animated:completion with valid UIViewControllers
[self setupPagesWithIndex:0]; 

self.pageViewController.delegate = self;
self.pageViewController.dataSource = self;

self.view.frame = CGRectMake(0, 0, 1024, 768);

self.pageViewController.view.backgroundColor = [UIColor grayColor];

Here is where I set the view controllers...

- (void) setupPagesWithIndex:(NSInteger) index
{
    UIViewController* vc1 = [self uicontrollerForIndex:index];
    UIViewController* vc2 = [self uicontrollerForIndex:index+1];
    [self.pageViewController setViewControllers:[NSArray arrayWithObjects:vc1,vc2, nil] 
                                      direction:UIPageViewControllerNavigationDirectionForward 
                                       animated:NO 
                                     completion:nil];
}

The only thing that appears on screen is the grey background color. I have verified that the UIViewControllers are valid, have good frames and I even gave them background colors just so I could see something

This is how I'm adding the UIPageViewController to the screen:

 [[self rootViewController] addChildViewController:self.pageViewController];
 [[self rootViewController].view addSubview:self.pageViewController.view];

[self rootViewController] returns the application's rootViewController.

The view is definitely visible, because I can see the backgroundcolor I apply... however, the UIPageViewController is just totally blank!

I implemented all of the datasource and delegate methods and adopted the protocols; they never even get called!

My question is; what are all of the requirements for the UIPageViewController to display pages when you do everything programmatically?

edit #1, per request: This class is a controller for UIPageViewController within my own application-building framework. I'm giving the controller two ways of building a page right now -- from an image name or from a kind of asset key. In either case, it ultimately returns a view which I wrap with a UIViewController.

I create the view controller with

UIViewController* vc = [[[PageTest alloc] initWithNibName:@"PageTest" bundle:nil] autorelease];

'PageTest' is just a UIViewController with a corresponding nib, which is blank except for the auto-generated settings. I then add my custom view as a subview to this view controller. This is what comes back from uicontrollerForIndex:

edit #2, further discovery

I've found a way to show the book flipper; if I only initialize it with one view controller it will show the book flipper. It doesn't matter if the two view controllers are different classes entirely; if I setViewControllers with two of them then nothing shows.

if I return UIPageViewControllerSpineLocationMid in the delegate method

- (UIPageViewControllerSpineLocation)pageViewController:(UIPageViewController *)pageViewController spineLocationForInterfaceOrientation:(UIInterfaceOrientation)orientation

Then upon rotation, the app will crash without an identifiable backtrace.

Answer 1

With the,

 - (UIPageViewControllerSpineLocation)pageViewController:(UIPageViewController *)pageViewController spineLocationForInterfaceOrientation:(UIInterfaceOrientation)orientation

method, you must call setViewControllers before returning the spineLocation.