UINavigationController remove drop shadow when transitioning to another VC

Question

When using a UINavigationController and pushViewController:animated: to push another view controller onto the stack, there is always a drop shadow shown during the transition:

I have an app where I have a video background on the navigation controller, so I want to remove that drop shadow since it looks strange during the transition.

Is there any way to completely remove it? (I am NOT talking about UINavigationBar shadow)

Answer 1

Solution:

// set one of viewcontrollers (usual first) as navigationController delegate

class ViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()

        navigationController?.delegate = self
    }

}

// make the view controller conform to `UINavigationControllerDelegate`

extension ViewController: UINavigationControllerDelegate {
    func navigationController(_ navigationController: UINavigationController, animationControllerFor operation: UINavigationControllerOperation, from fromVC: UIViewController, to toVC: UIViewController) -> UIViewControllerAnimatedTransitioning? {
        return PushPopAnimator(operation: operation)
    }
}

// The animation controller

class PushPopAnimator: NSObject, UIViewControllerAnimatedTransitioning {
    let operation: UINavigationControllerOperation

    init(operation: UINavigationControllerOperation) {
        self.operation = operation
        super.init()
    }

    func transitionDuration(using transitionContext: UIViewControllerContextTransitioning?) -> TimeInterval {
        return 0.25
    }

    func animateTransition(using transitionContext: UIViewControllerContextTransitioning) {
        let from = transitionContext.viewController(forKey: .from)!
        let to   = transitionContext.viewController(forKey: .to)!

        let rightTransform = CGAffineTransform(translationX: transitionContext.containerView.bounds.size.width, y: 0)
        let leftTransform = CGAffineTransform(translationX: -transitionContext.containerView.bounds.size.width, y: 0)

        if operation == .push {
            to.view.transform = rightTransform
            transitionContext.containerView.addSubview(to.view)
            UIView.animate(withDuration: transitionDuration(using: transitionContext), animations: { 
                from.view.transform = leftTransform
                to.view.transform = .identity
            }, completion: { finished in
                from.view.transform = .identity
                transitionContext.completeTransition(!transitionContext.transitionWasCancelled)
            })
        } else if operation == .pop {
            to.view.transform = leftTransform
            transitionContext.containerView.insertSubview(to.view, belowSubview: from.view)
            UIView.animate(withDuration: transitionDuration(using: transitionContext), animations: {
                to.view.transform = .identity
                from.view.transform = rightTransform
            }, completion: { finished in
                from.view.transform = .identity
                transitionContext.completeTransition(!transitionContext.transitionWasCancelled)
            })
        }
    }
}