title: Different alpha for subviews in the same container
body: <p>I have a question similar to the <a href="https://stackoverflow.com/questions/1269637/can-you-override-a-parent-uiviews-alpha-value-on-one-of-its-subviews">Can you override a parent UIView&#39;s alpha value on one of its subviews?</a></p>
  
  <p>In some cases I want to show custom semi-transparent full-screen overlay view over current view. The trick is that I want it to have custom navigation bar at the top and some other contents (let it be label) and I'd like the navigation bar to be opaque i.e. paint over everything on the original view. At the same time I'd like all other contents to be semi-transparent. I don't want to interfere with main view's navigation bar because there might be no navigation bar at all. I'd like to create a single container view with navigation bar and all other contents on it and add it to the window. But none of combinations of background color and alpha for container, navigation bar and contents I can come up with seems to work. </p>
  
  <p>The question I found suggests that it is impossible if container view is not opaque. My case <em>might be</em> slightly different because there is a simple border-line between transparent and opaque parts. So I still hope that there is some easy way. Or do I have to manage opaque navigation bar and transparent contents views separately anyway?</p>