title: Push ViewController on Top of TabBarController
body: <p>I'm stuck on a problem I really don't know how to solve:</p>
  
  <p>I have a TabBarController defined in my AppDelegate.</p>
  
  <pre><code> UITabBarController *tabBarController = [[UITabBarController alloc] init];
  </code></pre>
  
  <p>In this TabBarController i have several other NavigationControllers which have UiVieController inside:</p>
  
  <pre><code>ProgramController *programContr = [[ProgrammController alloc] init];
  UINavigationController navControllerPro = [[UINavigationController alloc] initWithRootViewController:programContr];
  
  ManualController *manualContr = [[ManualController alloc] init];
  UINavigationController navControllerMan = [[UINavigationController alloc] initWithRootViewController:manualContr];
  </code></pre>
  
  <p>and i add the NavigationController to the TabBarController:</p>
  
  <pre><code>tabBarController.viewControllers = [NSArray arrayWithObjects:navControllerPro,navControllerMan, nil]; 
  </code></pre>
  
  <p>I set the tabBarController to the rootViewController:</p>
  
  <pre><code>self.window.rootViewController = tabBarController;
  [[self window] makeKeyAndVisible];
  </code></pre>
  
  <p>That works fine.
  Now i want to add a "Login Screen" on top of that.
  I did this with:</p>
  
  <pre><code>[tabBarController presentModalViewController:navControllerLogin animated:YES];
  </code></pre>
  
  <p>Now the TabBarController loads its content in the background even if the LoginViewController is in front. How to load the TabBarController only if a Button is pressed on the LoginViewController?</p>
  
  <p>Please help me.</p>