Fade Out TitleView on Swipe

Fade Out TitleView on Swipe

/**
 For configuring the NavigationBar to show/hide when user swipes
 - returns: void
*/
func configureNavigationBarAsHideable() {
   
   if let navigationController = self.navigationController {
       
       // respond to swipe and hide/show
       navigationController.hidesBarsOnSwipe = true
       
       // get the pan gesture used to trigger hiding/showing the NavigationBar
       let panGestureRecognizer = navigationController.barHideOnSwipeGestureRecognizer
       
       // when the user pans, call action method to fade out title view
       panGestureRecognizer.addTarget(self, action:"fadeOutTitleView:")
   }
}

/**
 For fading out the title view 
 - parameter sender: The UIPanGestureRecognizer when user swipes (and hides/shows NavigationBar))
 - returns: void
*/
func fadeOutTitleView(sender: UIPanGestureRecognizer) {
   
   if let titleView = self.navigationItem.titleView {
   
       // fade out title view when swiping up
       let translation = sender.translationInView(self.view)
       
       if(translation.y < 0) {
           
           let alphaValue = 1 - abs(translation.y / titleView.frame.height)
           
           titleView.alpha = alphaValue
       }
       
       // clear transparency if the Navigation Bar is not hidden after swiping
       if let navigationController = self.navigationController {
           
           let navigationBar = navigationController.navigationBar
           
           if navigationBar.frame.origin.y > 0 {
               
               if let titleView = self.navigationItem.titleView {
                   
                   titleView.alpha = 1
               }
           }
       }
   }
}