title: Glossy effect when clicking on UINavigationBar button
body: <p>When I'm clicking on a <code>UIButton</code> that located on the top of <code>UINavigationBar</code> I have this glossy effect:</p>
  
  <p><img src="https://i.stack.imgur.com/yOwXt.png" alt="glossy"></p>
  
  <p>How can I add this effect to another button that located on a <code>UINavigatonBar</code> but not as a left or right  button item? like this:</p>
  
  <pre><code>UIButton * emptyButton = [UIButton buttonWithType:UIButtonTypeCustom];
  [emptyButton setFrame:CGRectMake(119, 5, 82, 35)];
  [emptyButton addTarget:self action:@selector(centerNavigationBarTitleClicked:) forControlEvents:UIControlEventTouchUpInside];
  [emptyButton setBackgroundColor:[UIColor clearColor]];
  
  [self.navigationController.navigationBar addSubview:emptyButton];
  </code></pre>
  
  <p>Thanks!</p>