title: UIBarButtonItem Not Visible in QLPreviewController Toolbar
body: <p>I have a subclass of QLPreviewController that I'm pushing into a UINavigationController.  I am able to show/hide the bottom toolbar using:</p>
  
  <pre><code>- (void)viewWillAppear:(BOOL)animated
  {
      [super viewWillAppear:animated];
      self.navigationController.toolbarHidden = NO;
  }
  
  - (void)viewWillDisappear:(BOOL)animated
  {
      [super viewWillDisappear:animated];
      self.navigationController.toolbarHidden = YES;
  }
  </code></pre>
  
  <p>But items I'm adding to the toolbar aren't showing up:</p>
  
  <pre><code>- (void)viewDidLoad
  {
      [super viewDidLoad];
      UIBarButtonItem *testButtonItem = [[UIBarButtonItem alloc] initWithTitle:@"Test"
                                                                         style:UIBarButtonItemStylePlain
                                                                        target:self
                                                                        action:@selector(testButtonClicked:)];
  
      NSArray *myToolbarItems = [NSArray arrayWithObjects:testButtonItem, nil];
      self.toolbarItems       = myToolbarItems;
      [testButtonItem release];
  }
  </code></pre>
  
  <p>Any advice would be very appreciated.  Thanks.</p>