Can't zoom an image in UIScrollView

Question

I've been stuck on this for hours. All I want is an ImageView in a ScrollView. I want the contentMode to be set to aspect fill so the image fills the ImageView every time. I also want the user to be able to zoom and pan around the image. Here is my code:

import UIKit

class ViewController: UIViewController, UIScrollViewDelegate {

var scrollView: UIScrollView!
var imageView: UIImageView!

override func viewDidLoad() {

    super.viewDidLoad()

    let image = UIImage(named: "fish")!

    imageView = UIImageView(image: image)
    imageView.frame = CGRect(origin: CGPoint(x: 0, y: 0), size:image.size)
    imageView.contentMode = .scaleAspectFill

    scrollView = UIScrollView(frame: view.bounds)
    scrollView.backgroundColor = UIColor.black
    scrollView.contentSize = imageView.bounds.size

    scrollView.delegate = self

    scrollView.minimumZoomScale = 0.1
    scrollView.maximumZoomScale = 4.0
    scrollView.zoomScale = 1.0

    scrollView.addSubview(imageView)
    view.addSubview(scrollView)

}

func viewForZoomingInScrollView(scrollView: UIScrollView) -> UIView? {
    return imageView
}

}

First of all I can't zoom in or out, don't understand why. I set the delegate, implemented viewForZoomingInScrollView and set the maximumZoomScale from what I read that is required for zooming to work.

Secondly the image does not Aspect Fit the screen. The content mode setting does not seem to affect anything because when I set it to .scaleToFill the image is not squeezed into the screen and I can pan around it.

Image smaller than the screen: http://i.imgur.com/eEuy0En.png

Original: http://i.imgur.com/GtkKWKu.jpg

Image larger than the screen: http://i.imgur.com/1cH4rrk.png

Original: http://i.imgur.com/ThNhapb.jpg

The smaller image should aspect fill the screen but it doesn't and and the zooming does not work in both cases. I can only pan around the larger image.

Answer 1

Your issue is the typo in the UIScrollViewDelegate method

should be

func viewForZooming(in scrollView: UIScrollView) -> UIView?

Hope this helps you

Answer 2

Please try this:

    func viewForZooming(in scrollView: UIScrollView) -> UIView? {
        return imageView!
    }

    func scrollViewDidEndZooming(_ scrollView: UIScrollView, with view: UIView?, atScale scale: CGFloat) {
        self.scrollView.flashScrollIndicators()
    }

Answer 3

Create two outlets : ---

        @IBOutlet weak var scrollView: UIScrollView!
        @IBOutlet weak var imgPhoto: UIImageView!
        override func viewDidLoad() {
        super.viewDidLoad()
           scrollView.minimumZoomScale = 1.0
           scrollView.maximumZoomScale = 6.0
       }

      func viewForZooming(in scrollView: UIScrollView) -> UIView? {

    return imgPhoto
}

else on your code

         let image = UIImage(named: "fish")!

         imageView = UIImageView(image: image)
         imageView.frame = CGRect(origin: CGPoint(x: 0, y: 0), size:image.size)
         //        imageView.contentMode = .scaleAspectFill
         //        
         scrollView = UIScrollView(frame: view.bounds)
        //        scrollView.backgroundColor = UIColor.black
        //        scrollView.contentSize = imageView.bounds.size

          scrollView.delegate = self

        scrollView.minimumZoomScale = 0.1
        scrollView.maximumZoomScale = 4.0
      //scrollView.zoomScale = 1.0

       scrollView.addSubview(imageView)
       view.addSubview(scrollView)