Question 69050 in IOS Swift Question posted in
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How to draw a dot on an image with zoom in/out capability? – Ios swift

I have an imageview in scrollview (I followed this video https://www.youtube.com/watch?v=0Tz0vI721c8). I want to draw a green dot on that image at x=100, y=100 (from upper left corner of the image). When user zoom in/out and pan, the dot stays at that location (image coord 100,100). How do I do that? I am totally new to ios dev.

import UIKit

class ViewController: UIViewController {
    @IBOutlet weak var scrollView: UIScrollView!
    @IBOutlet weak var imageView: UIImageView!

    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view.
        setupScrollView()
    }

    func setupScrollView() {
        scrollView.delegate = self
    }

}

extension ViewController:UIScrollViewDelegate {
    func viewForZooming(in scrollView: UIScrollView) -> UIView? {
        return imageView
    }
}
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2

Answers


  1. 0

    Create a imageView(dot) to Frame layout, attach dot align top and leading to Frame layout.

    enter image description here
    enter image description here

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  2. 0

    Try ur relative object(dot) layout to absolute object(imageView).

        let dot = UIView.init()
    dot.backgroundColor = .red
    //Use layout
    dot.translatesAutoresizingMaskIntoConstraints = false
    scrollView.addSubview(dot)
    let left = dot.leadingAnchor.constraint(equalTo: imageView.leadingAnchor, constant: 100)
    let top = dot.topAnchor.constraint(equalTo: imageView.topAnchor, constant: 100)
    let width = dot.widthAnchor.constraint(equalToConstant: 10)
    let height = dot.heightAnchor.constraint(equalToConstant: 10)
    var layout:[NSLayoutConstraint] = [left,top,width,height]
    NSLayoutConstraint.activate(layout)
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