Swift 3: How do I pinch to scale and rotate UIImageView?

Question

I am really struggling to find tutorials online as well as already answered questions (I have tried them and they don\'t seem to work). I have a UIImageView that I have in t

Answer 1

You have a some problems in your code. First you need to add the UIGestureRecognizerDelegate to your view controller and make it your gesture recognizer delegate. and add the shouldRecognizeSimultaneously method and return true. Second when applying the scale you need to save the transform when the pinch begins and apply the scale in top of it:

class DraggableImageView: UIImageView {
    override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
        backgroundColor = .blue
    }
    override func touchesEnded(_ touches: Set<UITouch>, with event: UIEvent?) {
        backgroundColor = .green
    }
    override func touchesMoved(_ touches: Set<UITouch>, with event: UIEvent?) {
        if let position = touches.first?.location(in: superview){
            center = position
        }
    }
}

---

class ViewController: UIViewController, UIGestureRecognizerDelegate {

    var identity = CGAffineTransform.identity

    override func viewDidLoad() {
        super.viewDidLoad()
        view.backgroundColor = .white
        setupViews()

        let pinchGesture = UIPinchGestureRecognizer(target: self, action: #selector(scale))
        let rotationGesture = UIRotationGestureRecognizer(target: self, action: #selector(rotate))

        pinchGesture.delegate = self
        rotationGesture.delegate = self

        view.addGestureRecognizer(pinchGesture)
        view.addGestureRecognizer(rotationGesture)
    }
    let firstImageView: DraggableImageView = {
        let iv = DraggableImageView()
        iv.backgroundColor = .red
        iv.isUserInteractionEnabled = true
        return iv
    }()

    func setupViews() {
        view.addSubview(firstImageView)
        let firstImageWidth: CGFloat = 50
        let firstImageHeight: CGFloat = 50
        firstImageView.frame = CGRect(x: view.frame.midX - firstImageWidth / 2, y: view.frame.midY - firstImageWidth / 2, width: firstImageWidth, height: firstImageHeight)
    }
    @objc func scale(_ gesture: UIPinchGestureRecognizer) {
        switch gesture.state {
        case .began:
            identity = firstImageView.transform
        case .changed,.ended:
            firstImageView.transform = identity.scaledBy(x: gesture.scale, y: gesture.scale)
        case .cancelled:
            break
        default:
            break
        }
    }
    @objc func rotate(_ gesture: UIRotationGestureRecognizer) {
        firstImageView.transform = firstImageView.transform.rotated(by: gesture.rotation)
    }
    func gestureRecognizer(_ gestureRecognizer: UIGestureRecognizer, shouldRecognizeSimultaneouslyWith otherGestureRecognizer: UIGestureRecognizer) -> Bool {
        return true
    }
}