title: UIPageViewController doesn't work at all; totally blank
body: <p>So,</p>
  
  <p>I'm trying to use the <code>UIPageViewController</code> with a custom application workflow, but I'm implementing it exactly as recommended in the docs.</p>
  
  <pre><code> 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];
  </code></pre>
  
  <p>Here is where I set the view controllers...</p>
  
  <pre><code>- (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];
  }
  </code></pre>
  
  <p>The only thing that appears on screen is the grey background color. I have verified that the <code>UIViewControllers</code> are valid, have good frames and I even gave them background colors just so I could see <em>something</em></p>
  
  <p>This is how I'm adding the UIPageViewController to the screen:   </p>
  
  <pre><code> [[self rootViewController] addChildViewController:self.pageViewController];
   [[self rootViewController].view addSubview:self.pageViewController.view];
  </code></pre>
  
  <p><code>[self rootViewController]</code> returns the application's rootViewController.</p>
  
  <p>The view is definitely visible, because I can see the backgroundcolor I apply... however, the UIPageViewController is just totally blank!</p>
  
  <p>I implemented all of the datasource and delegate methods and adopted the protocols; they never even get called!</p>
  
  <p>My question is; what are all of the requirements for the UIPageViewController to display pages when you do everything programmatically?</p>
  
  <p>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.</p>
  
  <p>I create the view controller with</p>
  
  <pre><code>UIViewController* vc = [[[PageTest alloc] initWithNibName:@"PageTest" bundle:nil] autorelease];
  </code></pre>
  
  <p>'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:</p>
  
  <p>edit #2, further discovery</p>
  
  <p>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.</p>
  
  <p>if I return <code>UIPageViewControllerSpineLocationMid</code> in the delegate method</p>
  
  <pre><code>- (UIPageViewControllerSpineLocation)pageViewController:(UIPageViewController *)pageViewController spineLocationForInterfaceOrientation:(UIInterfaceOrientation)orientation
  </code></pre>
  
  <p>Then upon rotation, the app will crash without an identifiable backtrace.</p>