title: iPhone UIToolbar UIButtonItem highlighting
body: <p>I have subclassed <code>UIToolbar</code> and within it have created a set of <code>UIButtonItems</code>, all added in order and nicely spaced with flexible spaces.  I now want to toggle one of the <code>UIButtonItems</code> each time it is tapped (just like the shuffle button in iPod, white blue white blue.  I have maintained a reference to the <code>UIButtonItem</code>.</p>
  
  <pre><code>// interface
  UIButtonItem *_shuffleButton;      // released in dealloc
  
  // implementation
  UIImage *_shuffleButtonImage = [UIImage imageNamed:@"shuffle_icon_200x100.png"];
  _shuffleButton = [[UIBarButtonItem alloc] initWithImage:_shuffleButtonImage  style:UIBarButtonItemStylePlain target:self action:@selector(shuffleButtonTapped)];
  </code></pre>
  
  <p>So now in <code>shuffleButtonTapped</code> I want to do something like:</p>
  
  <pre><code>_shuffleButton.highlighted = YES;
  // or 
  _shuffleButton.selected = YES;
  </code></pre>
  
  <p>but neither of these work.</p>
  
  <p>I have searched high and low and after failing to find anything I am starting to think I am missing something, can anyone tell me what it might be??  Thanks.</p>