Custom Presentation basics with UIPresentationController and friends

custom-presentation.swift

/// The ring leader
final class ModalTransitioningDelegate: NSObject, UIViewControllerTransitioningDelegate {
    func presentationController(
        forPresented presented: UIViewController,
        presenting: UIViewController?,
        source: UIViewController
        ) -> UIPresentationController? {
        return PresentationController(presentedViewController: presented, presenting: presenting)
    }

    func animationController(forPresented presented: UIViewController, presenting: UIViewController, source: UIViewController) -> UIViewControllerAnimatedTransitioning? {
        return PresentationAnimator(presenting: true)
    }

    func animationController(forDismissed dismissed: UIViewController) -> UIViewControllerAnimatedTransitioning? {
        return PresentationAnimator(presenting: false)
    }
}

/// Provides actual animation
class PresentationAnimator: NSObject, UIViewControllerAnimatedTransitioning {
    let presenting: Bool

    init(presenting: Bool) {
        self.presenting = presenting
    }

    func transitionDuration(using transitionContext: UIViewControllerContextTransitioning?) -> TimeInterval {
        return 0.3
    }

    func animateTransition(using transitionContext: UIViewControllerContextTransitioning) {
        let key = presenting ? UITransitionContextViewControllerKey.to
            : UITransitionContextViewControllerKey.from

        let controller = transitionContext.viewController(forKey: key)!
        if presenting {
            transitionContext.containerView.addSubview(controller.view)
        }

        let presentedFrame = transitionContext.finalFrame(for: controller)
        var dismissedFrame = presentedFrame

        dismissedFrame.origin.y -= (presentedFrame.height * (presenting ? 1.2 : 2.0))

        let initialFrame = presenting ? dismissedFrame : presentedFrame
        let finalFrame = presenting ? presentedFrame : dismissedFrame

        let animationDuration = transitionDuration(using: transitionContext)
        controller.view.frame = initialFrame
        UIView.animate(
            withDuration: animationDuration,
            delay: 0,
            usingSpringWithDamping: 0.9,
            initialSpringVelocity: 0,
            options: UIView.AnimationOptions.curveEaseIn,
            animations: {
                controller.view.frame = finalFrame
        }) { finished in
            transitionContext.completeTransition(finished)
        }
    }
}

/// Provides orientation and framing. Also side-by-side animation
final class PresentationController: UIPresentationController {
    override var frameOfPresentedViewInContainerView: CGRect {
        var presentedViewFrame = CGRect.zero
        let containerBounds: CGRect = containerView?.bounds ?? .zero
        presentedViewFrame.size = size(
            forChildContentContainer: presentedViewController,
            withParentContainerSize: CGSize(width: containerBounds.size.width - 40, height: containerBounds.size.height)
        )
        presentedViewFrame.origin.x = 20.0
        presentedViewFrame.origin.y = 40.0
        return presentedViewFrame
    }

    override func size(
        forChildContentContainer container: UIContentContainer,
        withParentContainerSize parentSize: CGSize
        ) -> CGSize {
        return CGSize(width: parentSize.width, height: 60.0)
    }

    let dimmingView: UIView = UIView()

    override init(presentedViewController: UIViewController, presenting presentingViewController: UIViewController?) {
        super.init(presentedViewController: presentedViewController, presenting: presentingViewController)
        setupDimmingView()
    }

    func setupDimmingView() {
        dimmingView.backgroundColor = UIColor(white: 0, alpha: 0.5)
        let tap = UITapGestureRecognizer(target: self, action: #selector(dimmingViewTapped(gesture:)))
        dimmingView.addGestureRecognizer(tap)
    }

    @objc
    func dimmingViewTapped(gesture: UIGestureRecognizer) {
        if gesture.state == .ended {
            presentingViewController.dismiss(animated: true, completion: nil)
        }
    }

    override func presentationTransitionWillBegin() {
        dimmingView.frame = self.containerView!.bounds
        dimmingView.alpha = 0.0
        containerView?.insertSubview(dimmingView, at: 0)
        containerView?.layer.cornerRadius = 6.0
        if let coordinator = presentedViewController.transitionCoordinator {
            coordinator.animate(alongsideTransition: { _ in
                self.dimmingView.alpha = 1.0
            }, completion: nil)
        } else {
            dimmingView.alpha = 1.0
        }
    }

    override func dismissalTransitionWillBegin() {
        if let coordinator = presentedViewController.transitionCoordinator {
            coordinator.animate(alongsideTransition: { _ in
                self.dimmingView.alpha = 0.0
            }, completion: nil)
        } else {
            dimmingView.alpha = 0.0
        }
    }

    override func containerViewWillLayoutSubviews() {
        dimmingView.frame = containerView!.bounds
        presentedView?.frame = frameOfPresentedViewInContainerView
        presentedView?.layer.cornerRadius = 6.0
    }
}