Retrieve tapped UIButton in a running animation which can be slightly off the screen

Question

This is what the code (below) can look like:

import UIKit

class TornadoButton: UIButton {

    override func hitTest(_ point: CGPoint, with event: UIEvent?) -> UIView? {
        let pres = self.layer.presentation()!
        let suppt = self.convert(point, to: self.superview!)
        let prespt = self.superview!.layer.convert(suppt, to: pres)

        return super.hitTest(prespt, with: event)
    }
}

class TestViewController: UIViewController {

    override func viewDidAppear(_ animated: Bool) {
        super.viewDidAppear(animated)

        let greySubview = UIView()
        greySubview.backgroundColor = .red
        greySubview.translatesAutoresizingMaskIntoConstraints = false
        self.view.addSubview(greySubview)

        greySubview.centerXAnchor.constraint(equalTo: self.view.centerXAnchor).isActive = true
        greySubview.centerYAnchor.constraint(equalTo: self.view.centerYAnchor).isActive = true
        greySubview.widthAnchor.constraint(equalTo: self.view.widthAnchor).isActive = true
        greySubview.heightAnchor.constraint(equalTo: greySubview.widthAnchor).isActive = true

        let button = TornadoButton()
        greySubview.addSubview(button)
        button.translatesAutoresizingMaskIntoConstraints = false
        button.widthAnchor.constraint(equalTo: greySubview.widthAnchor, multiplier: 0.09).isActive = true
        button.heightAnchor.constraint(equalTo: greySubview.heightAnchor, multiplier: 0.2).isActive = true

        //below constrains are needed, else the origin of the UIBezierPath is wrong
        button.centerXAnchor.constraint(equalTo: greySubview.centerXAnchor).isActive = true
        button.centerYAnchor.constraint(equalTo: greySubview.centerYAnchor, constant: self.view.frame.height * 0.35).isActive = true
        self.view.layoutIfNeeded()

        button.addTarget(self, action: #selector(tappedOnCard(_:)), for: .touchUpInside)

        let circlePath = UIBezierPath(arcCenter: greySubview.frame.origin, radius: CGFloat(greySubview.frame.width * 0.5), startAngle: 0, endAngle: CGFloat.pi * 2, clockwise: true)

        let orbit = CAKeyframeAnimation(keyPath: "position")
        orbit.duration = 12
        orbit.path = circlePath.cgPath
        orbit.isAdditive = true
        orbit.repeatCount = Float.greatestFiniteMagnitude
        orbit.calculationMode = kCAAnimationPaced
        orbit.rotationMode = kCAAnimationRotateAuto

        button.layer.add(orbit, forKey: "orbit")
        button.backgroundColor = .blue

        let gr = UITapGestureRecognizer(target: self, action: #selector(onTap(gesture:)))
        greySubview.addGestureRecognizer(gr)
    }

    @objc func onTap(gesture:UITapGestureRecognizer) {
        let p = gesture.location(in: gesture.view)
        let v = gesture.view?.hitTest(p, with: nil)
    }

    @IBAction func tappedOnCard(_ sender: UIButton) {
        print(sender)
    }
}

This almost works, BUT:

I can retrieve the button if the button is 100% visible on the screen. If it is, for example, 50% visible (and 50% off the screen (look picture below)), I do not retrieve the buttons tap (aka not retrieve the print).

How can I retrieve the button while it is in a running animation and it can be slightly off the screen?

Answer 1

Original Answer:

It is very likely that the UITapGestureRecognizer in greySubview is consuming the touch and not letting it pass through to the button. Try this:

gr.cancelsTouchesInView = NO;

before adding the UITapGestureRecognizer to greySubview.

---

Edited Answer:

Please ignore my earlier answer and revert the change if you did it. My original answer did not make sense because in your case, the button is the subview of the grayView and cancelsTouchesInView works upwards in the view hierarchy, not downwards.

After a lot of digging, I was able to figure out why this was happening. It was because of incorrect hit testing in the TornadoButton during animation. Since you are animating the button, you will need to override the hitTest and the pointInside methods of the TornadoButton so that they account for the animated position instead of the actual position of the button when hit testing.

The default implementation of the pointInside method does not take into account the animated presentation layer of the button, and just tries to check for the touch point within the rect (which will fail because the touch was somewhere else).

The following implementations of the methods seem to do the trick:

class TornadoButton: UIButton{
    override func hitTest(_ point: CGPoint, with event: UIEvent?) -> UIView? {
        let pres = self.layer.presentation()!
        let suppt = self.convert(point, to: self.superview!)
        let prespt = self.superview!.layer.convert(suppt, to: pres)
        if (pres.hitTest(suppt)) != nil{
            return self
        }
        return super.hitTest(prespt, with: event)
    }

    override func point(inside point: CGPoint, with event: UIEvent?) -> Bool {
        let pres = self.layer.presentation()!
        let suppt = self.convert(point, to: self.superview!)
        return (pres.hitTest(suppt)) != nil
    }
}