when images Scroll then nav Bar updated - ios

Question

I have a array of Images and i'm moving images using scroll view and ALL WORKS FINE.
As i'm new in Swift so Now i need a solution for, When the images moving how can i check which image number(or image index number) is showing from total of images and then update Navigation bar accordingly.
Here is attached sample that i'm looking for:
code of Moving Images
class ImageScrollViewController: UIViewController {
#IBOutlet weak var mainScrollView: UIScrollView!
var imageArray = [UIImage]()
override func viewDidLoad() {
//mainScrollView.frame = view.frame
imageArray.append(UIImage(named: "nature-2")!)
imageArray.append(UIImage(named: "nature")!)
imageArray.append(UIImage(named: "nature4")!)
imageArray.append(UIImage(named: "nature5")!)
imageArray.append(UIImage(named: "nature6")!)
for i in 0..<imageArray.count{
let imageView = UIImageView()
imageView.image = imageArray[i]
imageView.contentMode = .scaleAspectFit
let xPosition = (self.view.frame.width * CGFloat(i)) + CGFloat(8)
imageView.frame = CGRect(x: xPosition , y: 0, width: self.mainScrollView.frame.width - CGFloat(16), height: self.mainScrollView.frame.height)
mainScrollView.contentSize.width = mainScrollView.frame.width * CGFloat(i+1)
mainScrollView.addSubview(imageView)
}
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
}
Hope so you guys, understand my Question.
Any help will be appreciated.
Thanks in Advance.

Answer 1

You can use contentOffset to continuously keep track of the position in UIScrollViewDelegate method scrollViewDidScroll.
So, if the screen is 1000px wide:
func scrollViewDidScroll(_ scrollView: UIScrollView) {
// how far from beginning of scrollView (ex: user scrolls 3300px to the right)
let scrollDistance = mainScrollView.contentOffset.x
// size of 1 image (each is 1000px wide + 8px spacing between images)
let sizeOfOneImage = self.view.frame.width + 8
// number of images scrolled (3300px scrolled right = ~3.3 images scrolled so far...)
let numberOfScreensScrolled = scrollDistance / sizeOfOneImage
// floor(#) turns 3.3 into 3 (removes everything after decimal)
var imageInteger = floor(numberOfScreensScrolled)
// need +1, or else 1st image will be "0", 2nd image will be "1", etc.
imageInteger = imageInteger + 1
// # / total
self.title = "\(imageInteger)/\(imageArray count)"
}
Below, + self.view.frame.width/2 exists to make the transition to the next number occur when ~50% of the next image is onscreen (can be changed to whatever seems best).
class ImageScrollViewController: UIViewController, UIScrollViewDelegate {
...
func scrollViewDidScroll(_ scrollView: UIScrollView) {
let imageInteger = floor((mainScrollView.contentOffset.x + self.view.frame.width/2) / (self.view.frame.width + 8)) + 1
self.title = "\(imageInteger)/\(imageArray count)"
}