Animate a view overlapping UINavigationBar ( Solution 2 - Move the view to key window then move back after a certain delay)

NavigationBarOverlappingDemo2.swift

//
//  NavigationBarOverlappingDemo2.swift
//
//  Created by Duc DoBa on 9/8/15.
//  Copyright (c) 2015 Duc Doba. All rights reserved.
//
//  This example is created to answer to the following StackOverflow question:
//  http://stackoverflow.com/questions/32446076/how-to-overlap-uinavigationbar-with-animation

import UIKit

class ViewController: UIViewController {
    // Simply put an UIImageView right under UINavigationBar to see the result
    @IBOutlet weak var imageView: UIImageView!
    var frameInSuperView: CGRect = CGRectZero
    var frameInWindow: CGRect = CGRectZero
    
    override func viewDidAppear(animated: Bool) {
        var longPress = UILongPressGestureRecognizer(target: self, action: Selector("longPress:"))
        imageView.addGestureRecognizer(longPress)
        imageView.userInteractionEnabled = true
    }
    
    func longPress(gesture:UILongPressGestureRecognizer) {
        if gesture.state == UIGestureRecognizerState.Began {
            println("user pressed on image")

            self.bringImageViewToWindow()
            
            let bounds = imageView.bounds
            UIView.animateWithDuration(
                0.5,
                delay: 0.0,
                usingSpringWithDamping: 0.4,
                initialSpringVelocity: 10,
                options: UIViewAnimationOptions.CurveEaseInOut,
                animations: {
                    self.imageView.bounds = CGRect(x: bounds.origin.x, y: bounds.origin.y, width: bounds.size.width + 50, height: bounds.size.height + 50)
                },
                completion: nil)
        }
        else if gesture.state == UIGestureRecognizerState.Changed {
            gesture.state == UIGestureRecognizerState.Began
        }
        else {
            println("user release on image")
            
            let bounds = imageView.bounds
            UIView.animateWithDuration(0.2, animations: {
                self.imageView.frame = self.frameInWindow
            }, completion: { finished in
                if finished {
                    self.bringImageViewBack()
                }
            })
        }
    }
    
    // This method is to ensure that the imageView will appear exactly at the point you want in the key window
    func bringImageViewToWindow() {
        let window = UIApplication.sharedApplication().keyWindow!
        let origin = imageView.superview!.convertPoint(imageView.frame.origin, toView: window)
        
        frameInSuperView = imageView.frame
        frameInWindow = CGRect(origin: origin, size: frameInSuperView.size)
        imageView.frame = frameInWindow
        
        window.addSubview(imageView)
    }
    
    func bringImageViewBack() {
        view.addSubview(imageView)
        
        // Without this block, the imageView will `disappear` magically for some reasons :-)
        let delay = 0.01 * Double(NSEC_PER_SEC)
        let time  = dispatch_time(DISPATCH_TIME_NOW, Int64(delay))
        dispatch_after(time, dispatch_get_main_queue(), {
          self.imageView.frame = self.frameInSuperView
        })
    }
}