Label text not updating after scroll event - ios

Question

I'm trying to update text of a label after a scroll event. I have a print command that prints the correct value but the label is not updating.
Here's my code
func scrollViewDidEndDecelerating(_ scrollView: UIScrollView) {
let x = scrollView.contentOffset.x
let w = scrollView.bounds.size.width
let p = Int(x/w)
print("page \(p)") // this prints correct value
self.signalLabel.text = signalText[Int(x/w)] // this does not update
}
what's the deal?
Here's the complete view controller code. This view is called from a button click on the initial view controller. This view contains a UIScrollView and UIPageControl. The UIScrollView contains two images that can be scrolled back and forth. I want to update the label text based on image that is shown.
import UIKit
class SignalOneViewController: UIViewController, UIScrollViewDelegate {
// MARK: Properties
#IBOutlet weak var signalScrollView: UIScrollView!
#IBOutlet weak var signalPageControl: UIPageControl!
#IBOutlet weak var signalLabel: UILabel!
// MARK: - Button Actions
#IBAction func signalOneButton(_ sender: Any) {
print("signal one button clicked")
performSegue(withIdentifier: "SignalOneSegue", sender: self)
}
#IBAction func onCancelButton(_ sender: Any) {
dismiss(animated: true, completion: nil)
}
let signalImages = ["signal1a.png", "signal1b.png"]
let signalText = ["Ready for play", "Untimed down"]
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view.
}
override func viewDidLayoutSubviews() {
self.loadScrollView()
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
func loadScrollView() {
let pageCount : CGFloat = CGFloat(signalImages.count)
signalLabel.text = signalText[0]
signalScrollView.backgroundColor = UIColor.clear
signalScrollView.delegate = self
signalScrollView.isPagingEnabled = true
signalScrollView.contentSize = CGSize(width: signalScrollView.frame.size.width * pageCount, height: signalScrollView.frame.size.height)
signalScrollView.showsHorizontalScrollIndicator = false
signalScrollView.showsVerticalScrollIndicator = false
signalPageControl.numberOfPages = Int(pageCount)
signalPageControl.pageIndicatorTintColor = UIColor.lightGray
signalPageControl.currentPageIndicatorTintColor = UIColor.blue
signalPageControl.addTarget(self, action: #selector(self.pageChanged), for: .valueChanged)
for i in 0..<Int(pageCount) {
print(self.signalScrollView.frame.size.width)
let image = UIImageView(frame: CGRect(x: self.signalScrollView.frame.size.width * CGFloat(i), y: 0, width: self.signalScrollView.frame.size.width, height: self.signalScrollView.frame.size.height))
image.image = UIImage(named: signalImages[i])!
image.contentMode = UIViewContentMode.scaleAspectFit
self.signalScrollView.addSubview(image)
}
}
//MARK: UIScrollView Delegate
func scrollViewDidScroll(_ scrollView: UIScrollView) {
let viewWidth: CGFloat = scrollView.frame.size.width
// content offset - tells by how much the scroll view has scrolled.
let pageNumber = floor((scrollView.contentOffset.x - viewWidth / 50) / viewWidth) + 1
signalPageControl.currentPage = Int(pageNumber)
}
func scrollViewDidEndDecelerating(_ scrollView: UIScrollView) {
let x = scrollView.contentOffset.x
let w = scrollView.bounds.size.width
let p = Int(x/w)
print("page \(p)")
self.signalLabel.text = signalText[p]
print(">>> \(signalText[Int(x/w)])")
}
//MARK: page tag action
#objc func pageChanged() {
let pageNumber = signalPageControl.currentPage
var frame = signalScrollView.frame
frame.origin.x = frame.size.width * CGFloat(pageNumber)
frame.origin.y = 0
signalScrollView.scrollRectToVisible(frame, animated: true)
}
}

Answer 1

Make sure signalLabe IBOutlet is attached to your label in storyboard or xib