在UIViewControllers之间传递UILongPressGestureRecognizer

Question

I've looked around on SO and other places online and haven't been able to find a solution yet. I have a UILongPressGestureRecognizer on one view controller which performs an animation on a UIView then presents another view controller (if the user does not move their finger during the animation). I would like to dismiss the second view controller when the user lifts their finger, but I am having trouble.

My current approach is adding another UILongPressGestureRecognizer to the second view controller and dismissing the view controller when its state is .ended; however I don't know how to tie the two gesture recognizers together so that I can start the touch in one view controller and end in another.

I have attached the relevant code below

In the first View Controller

   @objc private func pinAnimation(sender: UILongPressGestureRecognizer) {
    if let headerView = projectView.projectCollectionView.supplementaryView(forElementKind: UICollectionElementKindSectionHeader, at: IndexPath(row: 0, section: 0)) as? ProjectHeaderView {

        switch sender.state {
        case .began:
            let frame = headerView.pinButton.frame
            UIView.setAnimationCurve(.linear)

            UIView.animate(withDuration: 1, animations: {
                headerView.pinProgressView.frame = frame
            }, completion: { (_) in
                if (headerView.pinProgressView.frame == headerView.pinButton.frame) {
                    let notification = UINotificationFeedbackGenerator()
                    notification.notificationOccurred(.success)
                    let homeVC = HomeViewController()
                    self.present(homeVC, animated: true, completion: {

                        homeVC.longPress(sender)

                        let height = headerView.pinButton.frame.height
                        let minX = headerView.pinButton.frame.minX
                        let minY = headerView.pinButton.frame.minY
                        headerView.pinProgressView.frame = CGRect(x: minX, y: minY, width: 0, height: height)
                    })
                }
            })

        case .ended:
            //cancel current animation
            let height = headerView.pinProgressView.frame.height
            let minX = headerView.pinProgressView.frame.minX
            let minY = headerView.pinProgressView.frame.minY
            UIView.setAnimationCurve(.linear)
            UIView.animate(withDuration: 0.5) {
                headerView.pinProgressView.frame = CGRect(x: minX, y: minY, width: 0, height: height)
            }
        default:
            break
        }
    }
}

In the second View Controller

override func viewDidLoad() {
    super.viewDidLoad()
    let longPressRecognizer = UILongPressGestureRecognizer(target: self, action: #selector(longPress(_:)))
    view.addGestureRecognizer(longPressRecognizer)
}

@objc func longPress(_ sender: UILongPressGestureRecognizer) {
    switch sender.state {
    case .ended:
        self.dismiss(animated: true, completion: nil)
    default:
        break
    }
}

Any help / guidance will be much appreciated!

Answer 1

I would recommend you using delegate pattern:

Create delegate for your first ViewController

protocol FirstViewControllerDelegate {
    func longPressEnded() 
}

then add delegate variable to your first ViewController

class FirstViewController {
    var delegate: FirstViewControllerDelegate?
    ...
}

next call method on delegate when long press ended

@objc private func pinAnimation(sender: UILongPressGestureRecognizer) {
    ...
    switch sender.state {
    case .began:
        ...
    case .ended:
        ...
        delegate?.longPressEnded()
    default:
        break
    }
}

after that when you're presenting second ViewController, set first ViewController's delegate as homeVC

let homeVC = HomeViewController()
self.delegate = homeVC

then implement this delegate to second ViewController and define what should happen when long press ended

class HomeViewController: UIViewController, FirstViewControllerDelegate {
    ...
    func longPressEnded() {
        dismiss(animated: true, completion: nil)
    }
}