Swift: Instantiate a view controller for custom transition in the current navigation stack - ios

Question

Introduction
I'm creating an app that has, in its rootViewController, a UITableView and a UIPanGestureRecognizer attached to a small UIView acting as a "handle" which enables a custom view controller transition for a UIViewController called "SlideOutViewController" to be panned from the right.
Issue
I have noticed two issues with my approach. But the actual custom transition works as expected.
When the SlideOutViewController is created it is not attached to the navigation stack I believe, therefore it has no associated navigationBar. And if I use the navigationController to push it on the stack, I loose the interactive transition.
Side note: I have not found a way to connect the handle to the SlideOutViewController that is interactively dragged out. So the translation of the handle is not consistent with the SlideOutViewControllers position.
Question
How can I add the SlideOutViewController to the navigation stack? So that the SlideOutViewController transitions with a navigationBar when I trigger the UIPanGestureRecognizer?
My code
In the rootViewController.
class RootViewController: UIViewController {
...
let slideControllerHandle = UIView()
var interactionController : UIPercentDrivenInteractiveTransition?
override func viewDidLoad() {
super.viewDidLoad()
... // Setting up the table view etc...
setupPanGForSlideOutController()
}
private func setupPanGForSlideOutController() {
slideControllerHandle.translatesAutoresizingMaskIntoConstraints = false
slideControllerHandle.layer.borderColor = UIColor.black.cgColor
slideControllerHandle.layer.borderWidth = 1
slideControllerHandle.layer.cornerRadius = 30
view.addSubview(slideControllerHandle)
slideControllerHandle.frame = CGRect(x: view.frame.width - 12.5, y: view.frame.height / 2, width: 25, height: 60)
let panGestureForCalendar = UIPanGestureRecognizer(target: self, action: #selector(handlePanGestureForSlideOutViewController(_:)))
slideControllerHandle.addGestureRecognizer(panGestureForCalendar)
}
#objc private func handlePanGestureForSlideOutViewController(_ gesture: UIPanGestureRecognizer) {
let xPosition = gesture.location(in: view).x
let percent = 1 - (xPosition / view.frame.size.width)
switch gesture.state {
case .began:
guard let slideOutController = storyboard?.instantiateViewController(withIdentifier: "CNSlideOutViewControllerID") as? SlideOutViewController else { fatalError("Sigh...") }
interactionController = UIPercentDrivenInteractiveTransition()
slideOutController.customTransitionDelegate.interactionController = interactionController
self.present(slideOutController, animated: true)
case .changed:
slideControllerHandle.center = CGPoint(x: xPosition, y: slideControllerHandle.center.y)
interactionController?.update(percent)
case .ended, .cancelled:
let velocity = gesture.velocity(in: view)
interactionController?.completionSpeed = 0.999
if percent > 0.5 || velocity.x < 10 {
UIView.animate(withDuration: 0.5, delay: 0, usingSpringWithDamping: 0.8, initialSpringVelocity: 0.5, options: .curveEaseInOut, animations: {
self.slideControllerHandle.center = CGPoint(x: self.view.frame.width, y: self.slideControllerHandle.center.y)
})
interactionController?.finish()
} else {
UIView.animate(withDuration: 0.5, delay: 0, usingSpringWithDamping: 0.8, initialSpringVelocity: 0.5, options: .curveEaseInOut, animations: {
self.slideControllerHandle.center = CGPoint(x: -25, y: self.slideControllerHandle.center.y)
})
interactionController?.cancel()
}
interactionController = nil
default:
break
}
}
The SlideOutViewController
class SlideOutViewController: UIViewController {
var interactionController : UIPercentDrivenInteractiveTransition?
let customTransitionDelegate = TransitionDelegate()
required init?(coder aDecoder: NSCoder) {
super.init(coder: aDecoder)
modalPresentationStyle = .custom
transitioningDelegate = customTransitionDelegate
}
override func viewDidLoad() {
super.viewDidLoad()
view.backgroundColor = .red
navigationItem.title = "Slide Controller"
let addButton = UIBarButtonItem(barButtonSystemItem: .add, target: self, action: #selector(addNewData(_:)))
navigationItem.setRightBarButton(addButton, animated: true)
}
}
The custom transition code. Based on Rob's descriptive answer on this SO question
TransitionDelegate
class TransitioningDelegate: NSObject, UIViewControllerTransitioningDelegate {
weak var interactionController : UIPercentDrivenInteractiveTransition?
func animationController(forPresented presented: UIViewController, presenting: UIViewController, source: UIViewController) -> UIViewControllerAnimatedTransitioning? {
return CNRightDragAnimationController(transitionType: .presenting)
}
func animationController(forDismissed dismissed: UIViewController) -> UIViewControllerAnimatedTransitioning? {
return CNRightDragAnimationController(transitionType: .dismissing)
}
func presentationController(forPresented presented: UIViewController, presenting: UIViewController?, source: UIViewController) -> UIPresentationController? {
return PresentationController(presentedViewController: presented, presenting: presenting)
}
func interactionControllerForPresentation(using animator: UIViewControllerAnimatedTransitioning) -> UIViewControllerInteractiveTransitioning? {
return interactionController
}
func interactionControllerForDismissal(using animator: UIViewControllerAnimatedTransitioning) -> UIViewControllerInteractiveTransitioning? {
return interactionController
}
}
DragAnimatedTransitioning
class CNRightDragAnimationController: NSObject, UIViewControllerAnimatedTransitioning {
enum TransitionType {
case presenting
case dismissing
}
let transitionType: TransitionType
init(transitionType: TransitionType) {
self.transitionType = transitionType
super.init()
}
func animateTransition(using transitionContext: UIViewControllerContextTransitioning) {
let inView = transitionContext.containerView
let toView = transitionContext.view(forKey: .to)!
let fromView = transitionContext.view(forKey: .from)!
var frame = inView.bounds
switch transitionType {
case .presenting:
frame.origin.x = frame.size.width
toView.frame = frame
inView.addSubview(toView)
UIView.animate(withDuration: transitionDuration(using: transitionContext), animations: {
toView.frame = inView.bounds
}, completion: { finished in
transitionContext.completeTransition(!transitionContext.transitionWasCancelled)
})
case .dismissing:
toView.frame = frame
inView.insertSubview(toView, belowSubview: fromView)
UIView.animate(withDuration: transitionDuration(using: transitionContext), animations: {
frame.origin.x = frame.size.width
fromView.frame = frame
}, completion: { finished in
transitionContext.completeTransition(!transitionContext.transitionWasCancelled)
})
}
}
func transitionDuration(using transitionContext: UIViewControllerContextTransitioning?) -> TimeInterval {
return 0.5
}
}
PresentationController
class PresentationController: UIPresentationController {
override var shouldRemovePresentersView: Bool { return true }
}
Thanks for reading my question.

Answer 1

The animation code you’ve taken this from is for custom “present” (e.g. modal) transitions. But if you want a custom navigation as you push/pop when using a navigation controller, you specify a delegate for your UINavigationController and then return the appropriate transitioning delegate in navigationController(_:animationControllerFor:from:to:). And also implement navigationController(_:interactionControllerFor:) and return your interaction controller there.
E.g. I'd do something like:
class FirstViewController: UIViewController {
let navigationDelegate = CustomNavigationDelegate()
override func viewDidLoad() {
super.viewDidLoad()
navigationController?.delegate = navigationDelegate
navigationDelegate.addPushInteractionController(to: view)
}
override func viewDidAppear(_ animated: Bool) {
super.viewDidAppear(animated)
navigationDelegate.pushDestination = { [weak self] in
self?.storyboard?.instantiateViewController(withIdentifier: "Second")
}
}
}
Where:
class CustomNavigationDelegate: NSObject, UINavigationControllerDelegate {
var interactionController: UIPercentDrivenInteractiveTransition?
var current: UIViewController?
var pushDestination: (() -> UIViewController?)?
func navigationController(_ navigationController: UINavigationController,
animationControllerFor operation: UINavigationController.Operation,
from fromVC: UIViewController,
to toVC: UIViewController) -> UIViewControllerAnimatedTransitioning? {
return CustomNavigationAnimator(transitionType: operation)
}
func navigationController(_ navigationController: UINavigationController,
interactionControllerFor animationController: UIViewControllerAnimatedTransitioning) -> UIViewControllerInteractiveTransitioning? {
return interactionController
}
func navigationController(_ navigationController: UINavigationController, didShow viewController: UIViewController, animated: Bool) {
current = viewController
}
}
// MARK: - Push
extension CustomNavigationDelegate {
func addPushInteractionController(to view: UIView) {
let swipe = UIScreenEdgePanGestureRecognizer(target: self, action: #selector(handlePushGesture(_:)))
swipe.edges = [.right]
view.addGestureRecognizer(swipe)
}
#objc private func handlePushGesture(_ gesture: UIScreenEdgePanGestureRecognizer) {
guard let pushDestination = pushDestination else { return }
let position = gesture.translation(in: gesture.view)
let percentComplete = min(-position.x / gesture.view!.bounds.width, 1.0)
switch gesture.state {
case .began:
interactionController = UIPercentDrivenInteractiveTransition()
guard let controller = pushDestination() else { fatalError("No push destination") }
current?.navigationController?.pushViewController(controller, animated: true)
case .changed:
interactionController?.update(percentComplete)
case .ended, .cancelled:
let speed = gesture.velocity(in: gesture.view)
if speed.x < 0 || (speed.x == 0 && percentComplete > 0.5) {
interactionController?.finish()
} else {
interactionController?.cancel()
}
interactionController = nil
default:
break
}
}
}
// MARK: - Pop
extension CustomNavigationDelegate {
func addPopInteractionController(to view: UIView) {
let swipe = UIScreenEdgePanGestureRecognizer(target: self, action: #selector(handlePopGesture(_:)))
swipe.edges = [.left]
view.addGestureRecognizer(swipe)
}
#objc private func handlePopGesture(_ gesture: UIScreenEdgePanGestureRecognizer) {
let position = gesture.translation(in: gesture.view)
let percentComplete = min(position.x / gesture.view!.bounds.width, 1)
switch gesture.state {
case .began:
interactionController = UIPercentDrivenInteractiveTransition()
current?.navigationController?.popViewController(animated: true)
case .changed:
interactionController?.update(percentComplete)
case .ended, .cancelled:
let speed = gesture.velocity(in: gesture.view)
if speed.x > 0 || (speed.x == 0 && percentComplete > 0.5) {
interactionController?.finish()
} else {
interactionController?.cancel()
}
interactionController = nil
default:
break
}
}
}
And
class CustomNavigationAnimator: NSObject, UIViewControllerAnimatedTransitioning {
let transitionType: UINavigationController.Operation
init(transitionType: UINavigationController.Operation) {
self.transitionType = transitionType
super.init()
}
func animateTransition(using transitionContext: UIViewControllerContextTransitioning) {
let inView = transitionContext.containerView
let toView = transitionContext.view(forKey: .to)!
let fromView = transitionContext.view(forKey: .from)!
var frame = inView.bounds
switch transitionType {
case .push:
frame.origin.x = frame.size.width
toView.frame = frame
inView.addSubview(toView)
UIView.animate(withDuration: transitionDuration(using: transitionContext), animations: {
toView.frame = inView.bounds
}, completion: { finished in
transitionContext.completeTransition(!transitionContext.transitionWasCancelled)
})
case .pop:
toView.frame = frame
inView.insertSubview(toView, belowSubview: fromView)
UIView.animate(withDuration: transitionDuration(using: transitionContext), animations: {
frame.origin.x = frame.size.width
fromView.frame = frame
}, completion: { finished in
transitionContext.completeTransition(!transitionContext.transitionWasCancelled)
})
case .none:
break
}
}
func transitionDuration(using transitionContext: UIViewControllerContextTransitioning?) -> TimeInterval {
return 0.5
}
}
Then, if the second view controller wanted to have the custom interactive pop plus the ability to swipe to the third view controller:
class SecondViewController: UIViewController {
var navigationDelegate: CustomNavigationDelegate { return navigationController!.delegate as! CustomNavigationDelegate }
override func viewDidLoad() {
super.viewDidLoad()
navigationDelegate.addPushInteractionController(to: view)
navigationDelegate.addPopInteractionController(to: view)
}
override func viewDidAppear(_ animated: Bool) {
super.viewDidAppear(animated)
navigationDelegate.pushDestination = { [weak self] in
self?.storyboard?.instantiateViewController(withIdentifier: "Third")
}
}
}
But if the last view controller can't push to anything, but only pop:
class ThirdViewController: UIViewController {
var navigationDelegate: CustomNavigationDelegate { return navigationController!.delegate as! CustomNavigationDelegate }
override func viewDidLoad() {
super.viewDidLoad()
navigationDelegate.addPopInteractionController(to: view)
}
override func viewDidAppear(_ animated: Bool) {
super.viewDidAppear(animated)
navigationDelegate.pushDestination = nil
}
}