CustomAlertPresentationController/CustomAlertPresentationController.swift at master · daveneff/CustomAlertPresentationController · GitHub

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//
//  CustomAlertPresentationController.swift
//
//  Created by Dave Neff
//

import UIKit

final class CustomAlertPresentationController: UIPresentationController {

    private lazy var dimmingView = UIView()

    override var frameOfPresentedViewInContainerView: CGRect {
        guard let containerView = containerView else { fatalError("containerView is nil") }

        let containerViewBounds = containerView.bounds

        var presentedViewFrame: CGRect = .zero

        presentedViewFrame.size = size(forChildContentContainer: presentedViewController,
                                       withParentContainerSize: containerViewBounds.size)
        presentedViewFrame.origin.x = (containerViewBounds.size.width - presentedViewFrame.size.width) / 2
        presentedViewFrame.origin.y = (containerViewBounds.size.height - presentedViewFrame.size.height) / 2

        return presentedViewFrame
    }

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

    override func containerViewWillLayoutSubviews() {
        guard let containerView = containerView else { return }
        presentedView?.frame = frameOfPresentedViewInContainerView
        dimmingView.frame = containerView.bounds
    }

    override func size(forChildContentContainer container: UIContentContainer, withParentContainerSize parentSize: CGSize) -> CGSize {
        let defaultAlertWidthMultiplier = 0.725
        let defaultAlertHeightMultiplier = 0.891

        return CGSize(width: parentSize.width * defaultAlertWidthMultiplier,
                      height: parentSize.width * defaultAlertHeightMultiplier)
    }

}

// MARK: - Presentation Animation

extension CustomAlertPresentationController {

    override func presentationTransitionWillBegin() {
        guard let containerView = containerView,
            let transitionCoordinator = presentedViewController.transitionCoordinator,
            let presentedView = presentedView else { fatalError("One of the required views are nil") }

        // Dimming view - initial frame
        containerView.insertSubview(dimmingView, at: 0)
        dimmingView.frame = containerView.bounds
        dimmingView.alpha = 0.0

        // Presented view - initial frame
        presentedView.layer.cornerRadius = Constants.cornerRadius
        presentedView.frame = frameOfPresentedViewInContainerView

        // Snapshot of presented view for CGAffine animation
        guard let presentedSnapshotView = presentedView.snapshotView(afterScreenUpdates: true) else { return }
        containerView.addSubview(presentedSnapshotView)
        presentedSnapshotView.frame = frameOfPresentedViewInContainerView
        presentedSnapshotView.transform = CGAffineTransform(scaleX: 1.15, y: 1.15)
        presentedSnapshotView.alpha = 0

        presentedView.alpha = 0

        transitionCoordinator.animate(
            alongsideTransition: { _ in
                self.dimmingView.alpha = 1.0
                presentedSnapshotView.transform = .identity
                presentedSnapshotView.alpha = 1
        },
            completion: { _ in
                presentedView.alpha = 1.0
                presentedSnapshotView.removeFromSuperview()
        })
    }
}

// MARK: - Dismissal Animation

extension CustomAlertPresentationController {

    override func dismissalTransitionWillBegin() {
        guard let transitionCoordinator = presentedViewController.transitionCoordinator else { fatalError("coordinator is nil") }

        transitionCoordinator.animate(
            alongsideTransition: { _ in
                self.dimmingView.alpha = 0.0
        },
            completion: { _ in
                self.dimmingView.removeFromSuperview()
        })
    }

}

// MARK: - Dimming View configuration

extension CustomAlertPresentationController {

    private func configureDimmingView() {
        dimmingView.backgroundColor = UIColor(white: 0.0, alpha: 0.50)
        dimmingView.addGestureRecognizer(UITapGestureRecognizer(target: self, action: #selector(onDimmingViewTapped)))
    }

    @objc func onDimmingViewTapped() {
        presentedViewController.view.endEditing(true)
    }

}