Interactive Controller Experiments

gistfile1.txt

//
//  InteractiveController.swift
//  iOS
//
//  Created by Chris Li on 1/22/18.
//  Copyright © 2018 Chris Li. All rights reserved.
//

import UIKit

class TestTableViewController: InteractiveController, UITableViewDataSource, UIGestureRecognizerDelegate {
    let tableView = UITableView()
    override func loadView() {
        view = tableView
        tableView.dataSource = self
        tableView.register(UITableViewCell.self, forCellReuseIdentifier: "cell")
    }
    
    override func viewDidLoad() {
        super.viewDidLoad()
        panGestureRecognizer.delegate = self
    }
    
    func numberOfSections(in tableView: UITableView) -> Int {
        return 1
    }
    
    func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        return 100
    }
    
    func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        let cell = tableView.dequeueReusableCell(withIdentifier: "cell", for: indexPath)
        cell.textLabel?.text = "\(indexPath.row)"
        return cell
    }
    
    func gestureRecognizer(_ gestureRecognizer: UIGestureRecognizer, shouldRecognizeSimultaneouslyWith otherGestureRecognizer: UIGestureRecognizer) -> Bool {
        let gestureRecognizer = (gestureRecognizer as! UIPanGestureRecognizer)
        let direction = gestureRecognizer.velocity(in: view).y
        if tableView.contentOffset.y == 0 && direction > 0 {
            tableView.isUserInteractionEnabled = false
        } else {
            tableView.isUserInteractionEnabled = true
        }
        
        return false
    }
}

class InteractiveController: UIViewController, UIViewControllerTransitioningDelegate {

    let panGestureRecognizer = UIPanGestureRecognizer()
    let dismissalTransition = InteractiveDismissalTransition()
    
    override func viewDidLoad() {
        super.viewDidLoad()
        view.addGestureRecognizer(panGestureRecognizer)
        panGestureRecognizer.addTarget(self, action: #selector(handleGestureRecognizer(gestureRecognizer:)))
        navigationItem.leftBarButtonItem = UIBarButtonItem(barButtonSystemItem: .done, target: self, action: #selector(dismissController))
    }
    
    @objc func dismissController() {
        dismissalTransition.wantsInteractiveStart = false
        dismiss(animated: true, completion: nil)
    }
    
    @objc func handleGestureRecognizer(gestureRecognizer: UIPanGestureRecognizer) {
        let location = gestureRecognizer.translation(in: gestureRecognizer.view?.superview)
        switch gestureRecognizer.state {
        case .began:
            dismissalTransition.wantsInteractiveStart = true
            dismiss(animated: true, completion: nil)
        case .changed:
            let progress = location.y / view.frame.height
            dismissalTransition.update(progress)
        case .cancelled:
            dismissalTransition.cancel()
        case .ended:
            let progress = location.y / view.frame.height
            let velocity = gestureRecognizer.velocity(in: gestureRecognizer.view?.superview)
            if velocity.y > 1000 {
                dismissalTransition.finish()
            } else if progress < 0.1 {
                dismissalTransition.cancel()
            } else if velocity.y < -100 {
                dismissalTransition.cancel()
            } else {
                dismissalTransition.finish()
            }
        default:
            break
        }
    }
    
    func animationController(forDismissed dismissed: UIViewController) -> UIViewControllerAnimatedTransitioning? {
        return dismissalTransition
    }
    
    func interactionControllerForDismissal(using animator: UIViewControllerAnimatedTransitioning) -> UIViewControllerInteractiveTransitioning? {
        return dismissalTransition
    }
}

class InteractiveDismissalTransition: UIPercentDrivenInteractiveTransition, UIViewControllerAnimatedTransitioning {
    override init() {
        super.init()
        timingCurve = UICubicTimingParameters(animationCurve: .easeInOut)
        completionSpeed = 0.9
    }
    
    func transitionDuration(using transitionContext: UIViewControllerContextTransitioning?) -> TimeInterval {
        return 0.25
    }
    
    func animateTransition(using transitionContext: UIViewControllerContextTransitioning) {
        animate(context: transitionContext)
    }
    
    func interruptibleAnimator(using transitionContext: UIViewControllerContextTransitioning) -> UIViewImplicitlyAnimating {
        let animator = UIViewPropertyAnimator(duration: transitionDuration(using: transitionContext), timingParameters: timingCurve ?? UICubicTimingParameters(animationCurve: .easeInOut))
        animator.addAnimations {
            self.animate(context: transitionContext)
        }
        return animator
    }
    
    private func animate(context: UIViewControllerContextTransitioning) {
        let container = context.containerView
        guard let fromView = context.view(forKey: .from) else {
            context.completeTransition(false)
            return
        }
        
        let constraints = container.constraints.filter({ ($0.firstItem === container && $0.secondItem === fromView) || ($0.firstItem === fromView && $0.secondItem === container) })
        NSLayoutConstraint.deactivate(constraints)
        fromView.translatesAutoresizingMaskIntoConstraints = false
        
        NSLayoutConstraint.activate([
            fromView.widthAnchor.constraint(equalTo: container.widthAnchor),
            fromView.heightAnchor.constraint(equalTo: container.heightAnchor),
            fromView.centerXAnchor.constraint(equalTo: container.centerXAnchor)])

        let topConstraint = fromView.topAnchor.constraint(equalTo: container.topAnchor)
        topConstraint.priority = .defaultHigh
        topConstraint.isActive = true

        let bottomConstraint = fromView.topAnchor.constraint(equalTo: container.bottomAnchor)
        bottomConstraint.priority = .defaultLow
        bottomConstraint.isActive = true

        container.layoutIfNeeded()
        UIView.animate(withDuration: transitionDuration(using: context), delay: 0.0, options: .curveEaseInOut, animations: {
            topConstraint.priority = .defaultLow
            bottomConstraint.priority = .defaultHigh
            container.layoutIfNeeded()
        }) { (completed) in
            if context.transitionWasCancelled || !completed {
                topConstraint.priority = .defaultHigh
                bottomConstraint.priority = .defaultLow
                context.completeTransition(false)
            } else {
                context.completeTransition(true)
            }
        }
    }
}