title: setToolbarItems issue
body: <p>I added toolbar to on screen of navigation based application using the following code </p>
  
  <pre><code>    //Create an array to hold the list of bar button items
      NSMutableArray *items = [[NSMutableArray alloc] initWithCapacity:3];
  
  
      //Add buttons
  
      //load the image
      UIImage *buttonImage ;
  
  
      buttonImage = [UIImage imageNamed:@"test.png"];
  
  
  
      //create the button and assign the image for window width and level
      UIButton *button = [UIButton buttonWithType:UIButtonTypeCustom];
      [button addTarget:self action:@selector(WWL:) forControlEvents:UIControlEventTouchUpInside];
      [button setImage:buttonImage forState:UIControlStateNormal];
      //set the frame of the button to the size of the image (see note below)
      button.frame = CGRectMake(0, 0, buttonImage.size.width, buttonImage.size.height);
      //create a UIBarButtonItem with the button as a custom view
      WindowWidthZoom = [[UIBarButtonItem alloc]  initWithCustomView:button  ];
      [items addObject:WindowWidthZoom ];
  
      [self setToolbarItems:items];
      [[self navigationController] setToolbarHidden:NO animated:NO];
  </code></pre>
  
  <p>but when leave the screen , I noticed that the toolbar didn't disappear in the other screens , any suggestion how to hide it before leaving this screen to avoid its presence in other screens , and how to change its color to black </p>