title: use UIVisualEffectView to create a blur view, correct on simulator but not on iphone & ipad
body: <p>The goal: create a blur view in app.</p>
  
  <p>The code I use:</p>
  
  <pre><code>func createBlurBackgroundView() 
  {
      if !UIAccessibilityIsReduceTransparencyEnabled() 
      {
          if blurredSubView == nil || blurredSubView.superview == nil 
          {
              print("Create blurred background view")
              self.backgroundColor = UIColor.clearColor()
              let blurEffect = UIBlurEffect(style: UIBlurEffectStyle.Light)
              blurredSubView = UIVisualEffectView(effect: blurEffect)
              blurredSubView.frame = self.bounds
              self.insertSubview(blurredSubView, atIndex: 0)
          }
      }
      else 
      {
          print("Transparency disabled!! no blur view")
      }
  }
  </code></pre>
  
  <p>The result:
  everything works fine on the simulator:</p>
  
  <p><a href="https://i.stack.imgur.com/rdWWsl.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/rdWWsl.png" alt="enter image description here"></a></p>
  
  <p>But when I ran it on the iphone and ipads, it looks like:
  <a href="https://i.stack.imgur.com/0SuyAl.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/0SuyAl.jpg" alt="enter image description here"></a></p>
  
  <p>PLEASE NOTE I DIDN'T CHANGE THE "REDUCE TRANSPARENCY" SETTINGS!</p>
  
  <p>Then when I want to take a snapshot of this black background without blur, guess what?! in the photo stream, I saw exactly the correct blur view picture...</p>
  
  <p>Also, when I double clicked home button, and look at the multi-task interface, I saw the blur view effect!</p>
  
  <p><a href="https://i.stack.imgur.com/L3cuEl.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/L3cuEl.jpg" alt="enter image description here"></a></p>
  
  <p>More Info:
  I use iphone6s, ipad air2, both iOS 9.3.1
  Xcode version 7.3</p>
  
  <p>I'm so tired on trying to solve this problem, I tried other methods like take snapshot image and then apply blur effect on the image, but has other bugs and other CONs</p>