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May 28, 2024 19:05
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A UIViewController which is set up to be dismissed via a vertical pan (swipe down). Works even with a UIScrollView in the view.
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| protocol VerticalScrollInteractionViewDelegate: class { | |
| var canScroll: Bool { get set } | |
| var headerHeight: CGFloat { get set } | |
| } | |
| class CustomViewController: UIViewController, VerticalScrollInteractionViewDelegate { | |
| // VerticalScrollInteractionViewDelegate | |
| var canScroll: Bool = false | |
| var headerHeight: CGFloat = 0.0 | |
| var dismissalInteractiveTransition: ScrollDismissalInteractiveTransition? = nil | |
| var isInteractivelyDismissing: Bool { | |
| return dismissalInteractiveTransition != nil | |
| } | |
| init() { | |
| super.init(nibName: nil, bundle: nil) | |
| } | |
| override func loadView() { | |
| view = CustomView() | |
| } | |
| override func viewDidLoad() { | |
| super.viewDidLoad() | |
| // Add the gesture recognizer which will detect the interactive dismissal | |
| let panGesture = UIPanGestureRecognizer(target: self, action: #selector(handleTransitionPan)) | |
| panGesture.delegate = self | |
| view.addGestureRecognizer(panGesture) | |
| } | |
| override func viewDidAppear(_ animated: Bool) { | |
| super.viewDidAppear(animated) | |
| // Take control of transition delegate to interactively dismiss | |
| transitioningDelegate = self | |
| } | |
| override func viewDidLayoutSubviews() { | |
| // Set headerHeight to the `maxY` of your header (if you have one) | |
| super.viewDidLayoutSubviews() | |
| } | |
| required init?(coder aDecoder: NSCoder) { | |
| fatalError("init(coder:) has not been implemented") | |
| } | |
| } | |
| extension CustomViewController: UIViewControllerTransitioningDelegate { | |
| @objc func handleTransitionPan(recognizer: UIPanGestureRecognizer) { | |
| switch(recognizer.state) { | |
| case .began: | |
| attemptDismissalTransition(recognizer: recognizer) | |
| case .changed: | |
| if let interactive = dismissalInteractiveTransition { | |
| interactive.changed(recognizer: recognizer) | |
| } else { | |
| attemptDismissalTransition(recognizer: recognizer) | |
| } | |
| case .ended: | |
| dismissalInteractiveTransition?.ended(recognizer: recognizer) | |
| dismissalInteractiveTransition = nil | |
| default: | |
| break | |
| } | |
| } | |
| fileprivate func attemptDismissalTransition(recognizer: UIPanGestureRecognizer) { | |
| dismissalInteractiveTransition = ScrollDismissalInteractiveTransition(recognizer: recognizer, canScroll: canScroll, headerHeight: headerHeight) | |
| if(dismissalInteractiveTransition != nil) { | |
| // dismiss this view controller (preferably via delegation) | |
| dismiss(animated: true, completion: nil) | |
| } | |
| } | |
| func animationController(forPresented presented: UIViewController, presenting: UIViewController, source: UIViewController) -> UIViewControllerAnimatedTransitioning? { | |
| return nil | |
| } | |
| func animationController(forDismissed dismissed: UIViewController) -> UIViewControllerAnimatedTransitioning? { | |
| // Create a custom UIViewControllerAnimatedTransitioning to return here. | |
| // A simple one that just translates the view would be sufficient to experiment. | |
| return AnimatedTransitionSubclass() | |
| } | |
| func interactionControllerForDismissal(using animator: UIViewControllerAnimatedTransitioning) -> UIViewControllerInteractiveTransitioning? { | |
| return dismissalInteractiveTransition | |
| } | |
| } | |
| extension CustomViewController: UIGestureRecognizerDelegate { | |
| func gestureRecognizer(_ gestureRecognizer: UIGestureRecognizer, shouldRecognizeSimultaneouslyWith otherGestureRecognizer: UIGestureRecognizer) -> Bool { | |
| // This allows the UICollectionView ScrollView to interact with the interactive dismissal UIPanGestureRecognizer | |
| let otherGestureIsDescendent = otherGestureRecognizer.view?.isDescendant(of: self.view) | |
| return otherGestureIsDescendent == true | |
| } | |
| } | |
| class ScrollDismissalInteractiveTransition: UIPercentDrivenInteractiveTransition { | |
| var initialTouchLocation: CGPoint | |
| var containerBounds: CGRect | |
| init?(recognizer: UIPanGestureRecognizer, canScroll: Bool, headerHeight: CGFloat) { | |
| guard let view = recognizer.view, let superview = view.superview else { return nil } | |
| let location = recognizer.location(in: superview) | |
| // canScroll will be true if the UIScrollViewDelegate detected the desired content offset | |
| // headerHeight can be used if there is a vertical gap at the top of your view which should always initiate the interactive dismissal when panned | |
| guard canScroll || location.y <= headerHeight else { return nil } | |
| initialTouchLocation = location | |
| containerBounds = view.bounds | |
| } | |
| func changed(recognizer: UIPanGestureRecognizer) { | |
| guard let view = recognizer.view, let superview = view.superview else { return } | |
| let touchLocation = recognizer.location(in: superview) | |
| // Progress direction is dragging down (positive y direction) | |
| let deltaY = touchLocation.y - initialTouchLocation.y | |
| guard deltaY > 0 else { update(0); return } | |
| let percentageComplete = deltaY / containerBounds.height | |
| update(percentageComplete) | |
| } | |
| func ended(recognizer: UIPanGestureRecognizer) { | |
| guard let view = recognizer.view, let superview = view.superview else { return } | |
| let velocity = recognizer.velocity(in: superview) | |
| guard velocity.y > 100.0 else { cancel(); return } | |
| finish() | |
| } | |
| } | |
| extension CustomView: UIScrollViewDelegate { | |
| // My CustomView would have a weak delegate to the CustomViewController to update `canScroll` | |
| // weak var scrollInteractionViewDelegate: VerticalScrollInteractionViewDelegate? | |
| func scrollViewWillBeginDragging(_ scrollView: UIScrollView) { | |
| scrollInteractionViewDelegate?.canScroll = false | |
| } | |
| func scrollViewDidScroll(_ scrollView: UIScrollView) { | |
| // The value `-150` here determines that dismissal begins at content offset -150 | |
| scrollInteractionViewDelegate?.canScroll = scrollView.contentOffset.y < -150 | |
| } | |
| } |
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