Large image in Scrollview pinch zoom not working

Question

I am building an application where I want to display a floor plan where the image is 1260x1000, larger than the size of my view controller. I want the user to be able to pan the image and zoom in and out, similar to how a map behaves in Mapview.

Below is the code in my view controller. When I run the simulator, the image is panning but the zooming in and out isn't working. Any suggestions on how to fix my code would be helpful.

class ViewController: UIViewController, UIScrollViewDelegate {
 var scrollView: UIScrollView!
    var imageView: UIImageView!

    override func viewDidLoad() {
        super.viewDidLoad()
        imageView = UIImageView(image: UIImage(named: "myMap.pdf"))
        scrollView = UIScrollView(frame: view.bounds)
        scrollView.contentSize = imageView.bounds.size
        scrollView.addSubview(imageView)
        scrollView.delegate = self
        scrollView.minimumZoomScale = 0.3
        scrollView.maximumZoomScale = 5
        view.addSubview(scrollView)
    }
       func viewForZoomingInScrollView(scrollView: UIScrollView) -> UIView? {
        return imageView
    }


}

Answer 1

Your function signature is wrong:

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

Note: If you want to be able to scale your pdf image while keeping the vector-based rendering (so it doesn't get blurry when zoomed), you should probably use PDFKit and a PDFView.

Add your myMap.pdf file to your bundle... not to your Asset Catalog.

import UIKit
import PDFKit

class ZoomingPDFViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()

        guard let fileURL = Bundle.main.url(forResource: "myMap", withExtension: "pdf") else {
            fatalError("Could not load myMap.pdf!")
        }

        // Add PDFView to view controller.
        let pdfView = PDFView(frame: self.view.bounds)
        pdfView.autoresizingMask = [.flexibleWidth, .flexibleHeight]
        self.view.addSubview(pdfView)

        // Load myMap.pdf file from app bundle.
        pdfView.document = PDFDocument(url: fileURL)

        pdfView.autoScales = true
        pdfView.maxScaleFactor = 5.0
        pdfView.minScaleFactor = pdfView.scaleFactorForSizeToFit

    }

}