title: Make a custom back button for UINavigationController
body: <p>I'm developping an app for iOS 4.2+.
  I subclassed my <code>UINavigationController</code> to insert two <code>UIImageView</code> and make the navigation bar look custom.
  Everything is working great but I have a little problem.
  I created custom <code>UIBarButtonItem</code> and inside my view controllers i put them with :</p>
  
  <pre><code>self.navigationItem.leftBarButtonItem = [[UIBarButtonItem alloc]initWithCustomView:backButton];
  </code></pre>
  
  <p>It works too but the problem is that to make this work I need to call it from:</p>
  
  <pre><code> - (void)viewDidAppear:(BOOL)animated ;
  </code></pre>
  
  <p>So it only appears after the animation and I can see the non customized button 1 second before the customized one replace it.</p>
  
  <p>(I tried with <code>viewWillAppear</code> but then nothing append in navigationbar)</p>
  
  <p>I would like to know if you have a solution that could correct this problem.</p>
  
  <p>PS: I never use IB, everything is made programmatically.</p>
  
  <p>Thanks from France !</p>
  
  <p>EDIT 1: here is the code that didn't show anything for <code>viewWillAppear</code>:</p>
  
  <pre><code>- (void)viewWillAppear:(BOOL)animated  {
      [self setTitle:@"Jeu"];
  
      //Bouton testflight
      TIFButton *testFeedbackButton = [[TIFButton alloc]init];
      [testFeedbackButton setTitle: @"Envoyer un Feedback" forState:UIControlStateNormal];
      [testFeedbackButton addTarget:self action:@selector(launchFeedback) forControlEvents:UIControlEventTouchUpInside];
  
      UIBarButtonItem *testFeedback = [[UIBarButtonItem alloc] initWithCustomView:testFeedbackButton];
  
      self.navigationItem.rightBarButtonItem = testFeedback;  
  
      TIFBackButton *backButton = [[TIFBackButton alloc]init];
      [backButton setTitle: @"Retour" forState:UIControlStateNormal];
      [backButton addTarget:self action:@selector(popToPrecedentViewController) forControlEvents:UIControlEventTouchUpInside];
  
      self.navigationItem.leftBarButtonItem = [[UIBarButtonItem alloc]initWithCustomView:backButton];
  }
  </code></pre>