metatext/Transitions/ZoomDismissalInteractionController.swift

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Swift
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// Copyright © 2020 Metabolist. All rights reserved.
import UIKit
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final class ZoomDismissalInteractionController: NSObject {
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var transitionContext: UIViewControllerContextTransitioning?
var animator: UIViewControllerAnimatedTransitioning?
var fromReferenceViewFrame: CGRect?
var toReferenceViewFrame: CGRect?
// swiftlint:disable:next function_body_length
func didPanWith(gestureRecognizer: UIPanGestureRecognizer) {
guard let transitionContext = self.transitionContext,
let animator = self.animator as? ZoomAnimator,
let transitionView = animator.transitionView,
let fromVC = transitionContext.viewController(forKey: .from),
let toVC = transitionContext.viewController(forKey: .to),
let fromReferenceView = animator.fromDelegate?.referenceView(for: animator),
let fromReferenceViewFrame = self.fromReferenceViewFrame
else { return }
let toReferenceView = animator.toDelegate?.referenceView(for: animator)
fromReferenceView.isHidden = true
let anchorPoint = CGPoint(x: fromReferenceViewFrame.midX, y: fromReferenceViewFrame.midY)
let dismissThreshold = fromReferenceViewFrame.height / 8
let translatedPoint = gestureRecognizer.translation(in: fromReferenceView)
let backgroundAlpha = backgroundAlphaFor(view: fromVC.view, withPanningVerticalDelta: translatedPoint.y)
let scale = scaleFor(view: fromVC.view, withPanningVerticalDelta: translatedPoint.y)
fromVC.view.alpha = backgroundAlpha
transitionView.transform = CGAffineTransform(scaleX: scale, y: scale)
let newCenter = CGPoint(
x: anchorPoint.x + translatedPoint.x,
y: anchorPoint.y + translatedPoint.y - transitionView.frame.height * (1 - scale) / 2.0)
transitionView.center = newCenter
toReferenceView?.isHidden = true
transitionContext.updateInteractiveTransition(1 - scale)
toVC.tabBarController?.tabBar.alpha = 1 - backgroundAlpha
if gestureRecognizer.state == .ended {
if abs(anchorPoint.y - newCenter.y) < dismissThreshold {
// cancel
UIView.animate(
withDuration: 0.5,
delay: 0,
usingSpringWithDamping: 0.9,
initialSpringVelocity: 0,
options: []) {
transitionView.frame = fromReferenceViewFrame
fromVC.view.alpha = 1.0
toVC.tabBarController?.tabBar.alpha = 0
} completion: { _ in
toReferenceView?.isHidden = false
fromReferenceView.isHidden = false
transitionView.removeFromSuperview()
animator.transitionView = nil
transitionContext.cancelInteractiveTransition()
transitionContext.completeTransition(!transitionContext.transitionWasCancelled)
animator.toDelegate?.transitionDidEndWith(zoomAnimator: animator)
animator.fromDelegate?.transitionDidEndWith(zoomAnimator: animator)
self.transitionContext = nil
}
return
}
// start animation
UIView.animate(
withDuration: .shortAnimationDuration) {
fromVC.view.alpha = 0
if let toReferenceViewFrame = self.toReferenceViewFrame {
transitionView.frame = toReferenceViewFrame
} else {
transitionView.alpha = 0
}
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transitionView.layer.contentsRect = toReferenceView?.layer.contentsRect ?? .defaultContentsRect
transitionView.layer.cornerRadius = toReferenceView?.layer.cornerRadius ?? 0
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toVC.tabBarController?.tabBar.alpha = 1
} completion: { _ in
transitionView.removeFromSuperview()
toReferenceView?.isHidden = false
fromReferenceView.isHidden = false
self.transitionContext?.finishInteractiveTransition()
transitionContext.completeTransition(!transitionContext.transitionWasCancelled)
animator.toDelegate?.transitionDidEndWith(zoomAnimator: animator)
animator.fromDelegate?.transitionDidEndWith(zoomAnimator: animator)
self.transitionContext = nil
}
}
}
func backgroundAlphaFor(view: UIView, withPanningVerticalDelta verticalDelta: CGFloat) -> CGFloat {
let startingAlpha: CGFloat = 1.0
let finalAlpha: CGFloat = 0.0
let totalAvailableAlpha = startingAlpha - finalAlpha
let maximumDelta = view.bounds.height / 4.0
let deltaAsPercentageOfMaximun = min(abs(verticalDelta) / maximumDelta, 1.0)
return startingAlpha - (deltaAsPercentageOfMaximun * totalAvailableAlpha)
}
func scaleFor(view: UIView, withPanningVerticalDelta verticalDelta: CGFloat) -> CGFloat {
let startingScale: CGFloat = 1.0
let finalScale: CGFloat = 0.5
let totalAvailableScale = startingScale - finalScale
let maximumDelta = view.bounds.height / 2.0
let deltaAsPercentageOfMaximun = min(abs(verticalDelta) / maximumDelta, 1.0)
return startingScale - (deltaAsPercentageOfMaximun * totalAvailableScale)
}
}
extension ZoomDismissalInteractionController: UIViewControllerInteractiveTransitioning {
func startInteractiveTransition(_ transitionContext: UIViewControllerContextTransitioning) {
guard let animator = animator as? ZoomAnimator else { return }
animator.fromDelegate?.transitionWillStartWith(zoomAnimator: animator)
animator.toDelegate?.transitionWillStartWith(zoomAnimator: animator)
self.transitionContext = transitionContext
let containerView = transitionContext.containerView
guard
let fromVC = transitionContext.viewController(forKey: .from),
let toVC = transitionContext.viewController(forKey: .to),
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var fromReferenceViewFrame = animator.fromDelegate?.referenceViewFrameInTransitioningView(for: animator),
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let fromReferenceView = animator.fromDelegate?.referenceView(for: animator)
else { return }
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fromReferenceViewFrame = fromReferenceViewFrame.containsNaN ? .zero : fromReferenceViewFrame
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self.fromReferenceViewFrame = fromReferenceViewFrame
toReferenceViewFrame = animator.toDelegate?.referenceViewFrameInTransitioningView(for: animator)
containerView.insertSubview(toVC.view, belowSubview: fromVC.view)
if animator.transitionView == nil,
let transitionView = (fromReferenceView as? ZoomAnimatableView)?.transitionView() {
transitionView.frame = fromReferenceViewFrame
animator.transitionView = transitionView
containerView.addSubview(transitionView)
}
}
}