UIPageControl and UIScrollView not scrolling - ios

Question

I'm having a relatively simple UIViewController with a UIScrollView that's taking relatively half the screen and a UIImageView placed inside the UIScrollView that's the exact same size as the UIScrollView.
On top of the UIImageView there's a UIPageControl. The point is have a horizontal scrolling and present an image like a slider based on the amount of images in an array. The problem is that the scroll view is not scrolling and I don't know why.
#IBOutlet weak var scrollView: UIScrollView!
#IBOutlet weak var imageView: UIImageView!
#IBOutlet weak var pageControl: UIPageControl!
let imagelist = ["3.jpg", "1.jpg", "2.png", "4.png", "5.png"]
override func viewDidLoad() {
super.viewDidLoad()
scrollView.delegate = self
configurePageControl()
for i in stride(from: 0, to: imagelist.count, by: 1) {
var frame = CGRect.zero
frame.origin.x = self.scrollView.frame.size.width * CGFloat(i)
frame.origin.y = 0
frame.size = self.scrollView.frame.size
scrollView.isPagingEnabled = true
scrollView.isScrollEnabled = true
let myImage:UIImage = UIImage(named: imagelist[i])!
let bgColorFromImage = myImage.averageColor
imageView.image = myImage
imageView.contentMode = UIViewContentMode.scaleAspectFit
imageView.frame = frame
scrollView.backgroundColor = bgColorFromImage
scrollView.addSubview(imageView)
}
self.scrollView.contentSize = CGSize(width: self.scrollView.frame.size.width * CGFloat(imagelist.count), height: self.scrollView.frame.size.height)
pageControl.addTarget(self, action: #selector(changePage), for: UIControlEvents.valueChanged)
}
func configurePageControl() {
self.pageControl.numberOfPages = imagelist.count
self.pageControl.currentPage = 0
self.pageControl.tintColor = UIColor.red
self.pageControl.pageIndicatorTintColor = UIColor.black
self.pageControl.currentPageIndicatorTintColor = UIColor.green
self.imageView.addSubview(pageControl)
}
#objc func changePage() {
let x = CGFloat(pageControl.currentPage) * scrollView.frame.size.width
scrollView.setContentOffset(CGPoint(x: x,y :0), animated: true)
}
func scrollViewDidEndDecelerating(_ scrollView: UIScrollView) {
let pageNumber = round(scrollView.contentOffset.x / scrollView.frame.size.width)
pageControl.currentPage = Int(pageNumber)
}
This is what the UIStoryboard looks like:

Answer 1

Inside the for loop you use the same object of imageView , you only set the frame and the image
imageView.frame = frame
imageView.image = myImage
but you have to create a new instance of the UIImageView
//
Suppose you have a scrollView in IB with top , leading and trailing constraints to the superView , and a height of say 200 , you can add imageViews dynamically like this
class ViewController: UIViewController {
#IBOutlet weak var scrollView: UIScrollView!
override func viewDidLoad() {
super.viewDidLoad()
for i in 0..<10 {
let f = CGRect(x: CGFloat(i) * scrollView.frame.width, y: 0, width: scrollView.frame.width, height: scrollView.frame.height)
let imgV = UIImageView(frame: f)
imgV.image = UIImage(named: "re-fuel.png")
scrollView.addSubview(imgV)
}
scrollView.contentSize = CGSize(width: CGFloat(10) * scrollView.frame.width, height: scrollView.frame.height)
}
}
Result

Answer 2

The problem is that the scroll view itself is positioned with autolayout. Once you do that, you cannot set the contentSize to make the scroll view scrollable. You must use internal constraints to configure the content size.