title: Opacity only holds for a second
body: <p>I want to set opacity to 40% on the backgroundView in a UIViewcontroller  </p>
  
  <p>I have set the opacity in Storyboard:   </p>
  
  <p><a href="https://i.stack.imgur.com/HZMnc.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/HZMnc.png" alt="I have set the opacity in Storyboard:"></a></p>
  
  <p>It holds the correct opacity for about 1 second, and then the background turns completely black. </p>
  
  <p>I have not set the background color anywhere in <code>viewDidLoad</code> or anywhere else. </p>