title: How to create backBarButtomItem with custom view for a UINavigationController
body: <p>I have a <code>UINavigationController</code> into which I push several views. Inside <code>viewDidLoad</code> for one of these views I want to set the <code>self.navigationItem.backBarButtonItem</code> to a custom view (based on a custom image). I don't know why, but it doesn't seem to work. Instead, I get the standard "back" button.</p>
  
  <pre><code>UIButton *backButton = [[UIButton alloc] initWithFrame:CGRectMake(0, 0, 63, 30)];
  [backButton setImage:[UIImage imageNamed:@"back_OFF.png"] forState:UIControlStateNormal];
  [backButton setImage:[UIImage imageNamed:@"back_ON.png"] forState:UIControlStateSelected];
  UIBarButtonItem *backButtonItem = [[UIBarButtonItem alloc] initWithCustomView:backButton];
  self.navigationItem.backBarButtonItem = backButtonItem;
  [backButtonItem release];
  [backButton release];
  </code></pre>
  
  <p>I tested with a standard title and it worked. What is wrong with the above code ?</p>
  
  <pre><code>self.navigationItem.backBarButtonItem = [[[UIBarButtonItem alloc] initWithTitle:@"Prout" style:UIBarButtonItemStyleDone target:nil action:nil] autorelease];
  </code></pre>
  
  <p>Thanks for any help on this.</p>