Zoomable fullscreen image in portrait and landscape mode - swift

Question

I am a beginner at programming. I have an app where you can tap into any of the images that are on display to show that image in full-screen mode and can pinch to zoom. The issue I am having is that if you rotate the phone then the image is only half visible.
I'm using a scroll view to achieve the zoom functionality as that seems to be the consensus of the best way to do it.
It works perfectly in portrait mode, or if I enter the fullscreen image while the app is already in landscape orientation, but If I go into the landscape while in the fullscreen image that's where it goes wrong. Here is the code:
class PictureDetailViewController: UIViewController, UIScrollViewDelegate {
#IBOutlet weak var scrollView: UIScrollView!
var routeData = IndividualRoute(numberOfRoute: UserDefaults.standard.integer(forKey: "currentRoute"))
var detailPicture = UserDefaults.standard.bool(forKey: "segueFromDetailvc")
var detailImage = UIImageView()
override func viewDidLoad() {
super.viewDidLoad()
routeData.routesValues()
scrollView.delegate = self
selectImage()
scrollView.frame = UIScreen.main.bounds
scrollView.addSubview(detailImage)
scrollViewContents()
setupConstraints()
let scrollViewFrame = scrollView.frame
let scaleWidth = scrollViewFrame.size.width / scrollView.contentSize.width
let scaleHieght = scrollViewFrame.size.height / scrollView.contentSize.height
let minScale = min(scaleHieght, scaleWidth)
scrollView.minimumZoomScale = minScale
scrollView.maximumZoomScale = 1
scrollView.zoomScale = minScale
let tap = UITapGestureRecognizer(target: self, action: #selector(dismissFullscreen))
tap.numberOfTapsRequired = 2
view.addGestureRecognizer(tap)
}
//****************************************
//Image Setup
func setupConstraints() {
scrollView.translatesAutoresizingMaskIntoConstraints = false
NSLayoutConstraint.activate([
scrollView.leadingAnchor.constraint(equalTo: view.leadingAnchor),
scrollView.trailingAnchor.constraint(equalTo: view.trailingAnchor),
scrollView.topAnchor.constraint(equalTo: view.topAnchor),
scrollView.bottomAnchor.constraint(equalTo: view.bottomAnchor),
scrollView.centerXAnchor.constraint(equalTo: view.centerXAnchor),
scrollView.centerYAnchor.constraint(equalTo: view.centerYAnchor)])
scrollView.contentSize = (detailImage.image?.size)!
}
func selectImage() {
if !detailPicture {
let foo = "\(routeData.achievements[UserDefaults.standard.integer(forKey: "currentAchievement")])"
detailImage.image = UIImage(named: "\(foo.folding(options: .diacriticInsensitive, locale: nil)) 0")
} else {
let foo = "\(routeData.achievements[0])"
detailImage.image = UIImage(named: "\(foo.folding(options: .diacriticInsensitive, locale: nil)) 0")
print("\(foo.folding(options: .diacriticInsensitive, locale: nil)) 0")
}
guard let width = detailImage.image?.size.width else {
return
}
guard let height = detailImage.image?.size.height else {
return
}
let frame: CGRect = CGRect(x: 0, y: 0, width: width, height: height)
detailImage.frame = frame
detailImage.isUserInteractionEnabled = true
}
//**************************************
//Scrollview setup
#objc func dismissFullscreen(){
scrollView.setZoomScale(1, animated: true)
}
func scrollViewContents() {
let boundSize = UIScreen.main.bounds.size
var contentFrame = detailImage.frame
if contentFrame.size.width < boundSize.width {
contentFrame.origin.x = (boundSize.width - contentFrame.size.width) / 2
} else {
contentFrame.origin.x = 0
}
if contentFrame.size.height < boundSize.height {
contentFrame.origin.y = (boundSize.height - contentFrame.size.height) / 2
} else {
contentFrame.origin.y = 0
}
detailImage.frame = contentFrame
}
func scrollViewDidZoom(_ scrollView: UIScrollView) {
scrollViewContents()
}
func viewForZooming(in scrollView: UIScrollView) -> UIView? {
return detailImage
}
Sorry for posting so much code but its pretty much all relevant (I think).
Here are screenshots of the problem:

Answer 1

Okay, I've managed to fix it! Had a little jump around with delight.
I set up a new function called setupScale() that is called in viewdidload when the view is presented. I also added the viewwillLayoutSubview() override and called the setupScale() function inside it.
If looks like this:
private func setupScale() {
scrollView.frame = UIScreen.main.bounds
scrollView.contentSize = (detailImage.image?.size)!
scrollViewContents()
let scrollViewFrame = scrollView.frame
let scaleWidth = scrollViewFrame.size.width / scrollView.contentSize.width
let scaleHieght = scrollViewFrame.size.height / scrollView.contentSize.height
let minScale = min(scaleHieght, scaleWidth)
scrollView.minimumZoomScale = minScale
scrollView.maximumZoomScale = 1
scrollView.zoomScale = minScale
}
override func viewWillLayoutSubviews() {
setupScale()
}
Results look perfect on my iPad and iPhone 7 in landscape and portrait.