Making a android-desktop-style PageView

Question

This is a very simple example to achieve the android multi screen wallpaper effect on iOS, written in Swift. Sorry for the poor and redundant English as I am a non-native speaker and new to coding.

Many android phones have a multi screen desktop with the feature that when you swipe between screens, the wallpaper moves horizontally according to your gesture. Usually the wallpaper will move in a smaller scale comparing to the icons or search boxes to convey a sense of depth.

To do this, I use a UIScrollView instead of a UIPageViewController.I tried the latter at first, which makes the viewController hierarchy become very complex, and I couldn't use the touchesMove method correctly, as when you pan around pages, a new child viewController will come in and interrupt the method.

Instead, I tried UIScrollView and here is what I have reached.

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1. drag a wallpaper imageView into viewController, set the image, set the frame to (0,0,width of image, height of screen)
2. set the viewController size to freedom and set the width to theNumberOfPagesYouWantToDisplay * screenWidth (only to make the next steps easier, the width of the viewController will not affect the final result.)
3. drag a scrollView that fits in the viewController
4. add the "content UIs" into the scrollView to become a childView of it. Or you can do it using codes.
5. add a pageControl if you would like.

6. in your viewController.swift add the following code

   import UIKit
   
   class ViewController: UIViewController, UIScrollViewDelegate{
   
   let pagesToDisplay = 10 // You can modify this to test the result.
   let scrollViewWidth = CGFloat(320) 
   let scrollViewHeight = CGFloat(568) // You can also modify these based on the screen size of your device, this is an example for iPhone 5/5s
   
   @IBOutlet weak var backgroundView: UIImageView!
   @IBOutlet weak var scrollView: UIScrollView!
   @IBOutlet weak var pageControl: UIPageControl!
   
   override func viewDidLoad() {
       super.viewDidLoad()
       scrollView.delegate = self
       scrollView.pagingEnabled = true
       // Makes the scrollView feel like pageViewController.
       scrollView.frame = CGRectMake(0,0,scrollViewWidth,scrollViewHeight)
       //Remember to set the frame back to the screen size.
       scrollView.contentSize = CGSizeMake(CGFloat(pagesToDisplay) * scrollViewWidth, scrollViewHeight)
       pageControl.numberOfPages = pagesToDisplay
   }
   
   override func didReceiveMemoryWarning() {
       super.didReceiveMemoryWarning()
   }
   
   func scrollViewDidEndDecelerating(scrollView: UIScrollView) {
       let pageIndex = Int(scrollView.contentOffset.x / scrollView.frame.size.width)
       pageControl.currentPage = pageIndex
   }
   
   func scrollViewDidScroll(scrollView: UIScrollView) {
       let bgvMaxOffset = scrollView.frame.width - backgroundView.frame.width
       let svMaxOffset = scrollView.frame.width * CGFloat(pagesToDisplay - 1)
       if scrollView.contentOffset.x >= 0 &&
           scrollView.contentOffset.x <= svMaxOffset {
               backgroundView.frame.origin.x = scrollView.contentOffset.x * (bgvMaxOffset / svMaxOffset)
       }
   }
   }
   

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Feel free to try this on your device, and it will be really appreciated if someone could give some advice on this. Thank you.