DimBackgroundVC+PresentAnimator.swift

//
//  DimBackgroundVC+Animator.swift
//  guru_iOS
//
//  Created by kemchenj on 2018/10/4.
//  Copyright © 2018 gelonghui. All rights reserved.
//

import UIKit

extension DimBackgroundVC {

    class PresentAnimator: NSObject, UIViewControllerAnimatedTransitioning {
        func transitionDuration(using transitionContext: UIViewControllerContextTransitioning?) -> TimeInterval {
            return 0.33
        }

        func animateTransition(using transitionContext: UIViewControllerContextTransitioning) {
            guard
                let from = transitionContext.viewController(forKey: .from),
                let to = transitionContext.viewController(forKey: .to)
            else {
                assertionFailure()
                return
            }

            if let to = to as? DimBackgroundVC {
                to.view.frame = UIScreen.main.bounds
                to.view.backgroundColor = .clear
                to.view.layoutIfNeeded()

                transitionContext.containerView.addSubview(to.view)

                UIView.animate(
                    withDuration: 0.33,
                    delay: 0,
                    options: [],
                    animations: {
                        to.show()
                        to.view.layoutIfNeeded()
                        to.view.backgroundColor = UIColor.black.withAlphaComponent(0.3)
                    },
                    completion: { _ in
                        transitionContext.completeTransition(true)
                    }
                )
            } else if let from = from as? DimBackgroundVC {
                UIView.animate(
                    withDuration: 0.33,
                    delay: 0,
                    options: [],
                    animations: {
                        from.hide()
                        from.view.layoutIfNeeded()
                        from.view.backgroundColor = .clear
                    }, completion: { _ in
                        from.view.removeFromSuperview()
                        transitionContext.completeTransition(true)
                    }
                )
            } else {
                assertionFailure()
            }
        }
    }
}

DimBackgroundVC.swift

//
//  PopoverVC.swift
//  guru_iOS
//
//  Created by kemchenj on 2018/9/27.
//  Copyright © 2018 gelonghui. All rights reserved.
//

import UIKit

class DimBackgroundVC: UIViewController {

    private let animator = PresentAnimator()

    override init(nibName nibNameOrNil: String?, bundle nibBundleOrNil: Bundle?) {
        super.init(nibName: nibNameOrNil, bundle: nibBundleOrNil)
        setupTransition()
    }

    required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
        setupTransition()
    }

    func show() {}
    func hide() {}

    private func setupTransition() {
        modalPresentationStyle = .custom
        transitioningDelegate = self
    }
}

//
// MARK: - [ViewController] Life Cycle
//

extension DimBackgroundVC {

    override func viewDidLoad() {
        super.viewDidLoad()

        let tapGesture = UITapGestureRecognizer(target: self, action: #selector(_dismiss))
        tapGesture.delegate = self
        view.addGestureRecognizer(tapGesture)
    }
}

extension DimBackgroundVC {

    @objc
    private func _dismiss() {
        dismiss(animated: true, completion: nil)
    }
}

//
// MARK: - UIGestureRecognizerDelegate
//

extension DimBackgroundVC: UIGestureRecognizerDelegate {

    func gestureRecognizerShouldBegin(_ gestureRecognizer: UIGestureRecognizer) -> Bool {
        let location = gestureRecognizer.location(in: view)

        return view.subviews.find(element: { $0.frame.contains(location) }) == nil
    }
}

extension DimBackgroundVC: UIViewControllerTransitioningDelegate {

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

    func animationController(forDismissed dismissed: UIViewController) -> UIViewControllerAnimatedTransitioning? {
        return animator
    }
}