NavigationTransitionController

About

NavigationTransitionController is a UINavigationController that lets you implement interactive view controller transitions. It manages the UIViewControllerInteractiveTransitioning, UIViewControllerAnimatedTransitioning, and UIViewControllerTransitioningDelegate protocols for 4 unique transition types.
The current state of UIKit requires a UIViewController to conform to several protocols to implement a simple view controller transition. Not only that, but it also persists the standard UINavigationBar transition when pushing or popping a view controller onto a navigation stack. NavigationTransitionController solves the complexity of this implementation by wrapping all of the setup in a UINavigationController so that each UIViewController can interface with interactive, animated transitions with its own persisting UINavigationBar.

Usage

To simulate a view controller being "pushed" onto a standard navigation controller:

override func viewDidLoad() {
    super.viewDidLoad()
    // Initialize your view controller
    let myVC = UIViewController()
    // Pass it as a root view controller with the specified NavigationTransitionType
    let navigationTransitionController = NavigationTransitionController(rootViewController: myVC, type: .standard)
    navigationTransitionController.presentNavigation(self)
}

Presenting With Transition Types

The NavigationTransitionController comes out-of-the-box with 4 unique custom interactive animated transitions, accessible via the NavigationTransitionType enums:

NavigationTransitionType.Standard

This simulates a view controller being "pushed" onto a standard navigation controller:

NavigationTransitionType.Presentation

This simulates a view controller being "presented" from the bottom up. It restricts the root view controller's first scroll view subview without interfering its expected scrolling behavior (aka enable the transition to occur only when the UIScrollView's contentOffset reaches the top):

NavigationTransitionType.Fade

This simulates a view controller "fading-in" to the screen:

NavigationTransitionType.Zoom

This simulates the iOS photos library transition. Unlike other dependencies, the setup and teardown is incredibly simple:

To configure the initial view transition:

// Define your image view for the initial view transition
let imageView = UIImageView(frame: CGRect(x: 0.0, y: 0.0, width: 100.0, height: 100.0))

override func viewDidLoad() {
    super.viewDidLoad()
    // Setup
    view.addSubview(imageView)
    imageView.center = view.center

    // Initialize your view controller
    let photoVC = UIViewController()
    // MARK: - NavigationTransitionController
    // Pass it as a root view controller with the specified NavigationTransitionType — here, we specify the initial view as the imageView
    let navigationTransitionController = NavigationTransitionController(rootViewController: photoVC, type: .zoom, initialView: imageView)
    navigationTransitionController.presentNavigation(self)
}

If the view ever changes, (i.e, you're displaying multiple photos in a horizontally scrolling UICollectionView) update the NavigationTransitionController's finalView to persist the transitioning images to and from view controllers:

// Get the cell with the new image after we've scrolled and update the final view for the navigation transition controller's transition
if let cell = collectionView.cellForItem(at: indexPath) as? ImageCell {
    self.navigationTransitionController?.updateFinalView(cell.imageView)
}

Dismissing With Animation

You can access the NavigationTransitionController from within an arbitrary UIViewController that's presented with it as you would with the standard UINavigationController:

@objc func dismissViewController(_ sender: Any) {
    // Dismiss the navigation transition view controller by accessing it (it's a UINavigationController subclass so you can also use ```.navigationController``` and cast it) — also call a completion if needed
    self.navigationTransitionController?.dismissNavigation(animated: true, completion: { (dismissed: Bool) in
        // Closure executed here
    })
}

Observing Gesture-Driven Transitions

There are use-cases when one might need to observe a NavigationTransitionController's gesture-driven transitions. For instance, when we want to disable the scroll view from scrolling with a NavigationTransitionType.presentation transition:

    // Enable or disable the scroll view based on the UIGestureRecognizer.State
    self.navigationTransitionController?.interactiveTransitioningObserver = { (state: UIGestureRecognizer.State) in
        let isScrollEnabled = (state == .began || state == .changed) ? false : true
        self.scrollView.isScrollEnabled = isScrollEnabled
    }

Disabling the Gesture

To disable the gesture entirely:

    // Disable the gesture
    self.navigationTransitionController?.panGestureRecognizer.isEnabled = false

Requirements

• iOS 13+

Installation

To run the example project, clone the repo, and run pod install from the Example directory first.

NavigationTransitionController is available through CocoaPods. To install it, simply add the following line to your Podfile:

pod 'NavigationTransitionController'

Author

Nanolens, Inc.

License

NavigationTransitionController is available under the MIT license. See the LICENSE file for more info.