title: Make BlurView effect in TabBarController
body: <p>I have a ViewController inside a TabBarController, I want to add a BlurView in that ViewController, which also affects TabBarController, how to do that. </p>
  
  <p>If I use this code:</p>
  
  <pre><code>func presentBlurView() {
          blurEffect = UIBlurEffect(style: blurEffectStyle)
          blurView1 = UIView()
          blurView1!.frame = self.view.frame
          blurView1!.backgroundColor = UIColor(red: 0.0, green: 0.0, blue: 0.0, alpha: 0.5)
          self.view.addSubview(blurView1!)
  
          blurView1!.translatesAutoresizingMaskIntoConstraints = false
          NSLayoutConstraint.activateConstraints([
              blurView1!.leftAnchor.constraintEqualToAnchor(self.view.leftAnchor, constant: 0),
              blurView1!.topAnchor.constraintEqualToAnchor(self.view.topAnchor, constant: 0),
              blurView1!.rightAnchor.constraintEqualToAnchor(self.view.rightAnchor,constant:0),
              blurView1!.bottomAnchor.constraintEqualToAnchor(self.view.bottomAnchor,constant:0)
              ])
          let tapGestureRecognizer = UITapGestureRecognizer(target: self, action: "dismissProjectDetailViewRightSight:")
          tapGestureRecognizer.cancelsTouchesInView = false
          blurView1!.addGestureRecognizer(tapGestureRecognizer)
      }
  </code></pre>
  
  <p>It just shows inside the whole view of ViewController, not effect to TabBarController. But if I change like this:</p>
  
  <pre><code>UIApplication.sharedApplication().keyWindow?.addSubview(blurView1!)
  </code></pre>
  
  <p>It works with TabBarController, but in this case, very hard to handle somethings. Are there anyways to solve this problem. Any helps would be appreciated.</p>