CATransition在过渡期间逐渐褪黑

Question

I'm performing a simple right-to-left transition on two View Controllers. The animation works perfect, and exactly my desired result. However, due to the presenting / presented view controllers fading in / out, I get a black flash in the background.

My transition:

let transition = CATransition()
transition.duration = 2.25 // Slow duration to see the black.
transition.type = kCATransitionPush
transition.subtype = kCATransitionFromRight
view.window!.layer.add(transition, forKey: kCATransition)
present(vc, animated: false, completion: nil)

I read that setting the window color in AppDelegate didFinishLaunchingWithOptions can fix this, however, that doesn't appear to be doing anything. (The black is still visible during the transition.)

self.window!.backgroundColor = UIColor.white

Any advise on getting the two VC's to transition without the black flicker during the duration? Thanks.

Answer 1

I used to have exactly the same problem when doing custom transitions like you did above inside prepare(for:sender:) . I managed to solve it after reading A Beginner's Guide to Animated Custom Segues in iOS 8 .

Inside the Storyboard select your segue, pick custom kind and apply the custom SegueFromBottom class:

Here is the updated code for Swift 3.

import UIKit

class SegueFromBottom: UIStoryboardSegue
{
    override func perform()
    {
        // Assign the source and destination views to local variables.
        let firstVCView = self.source.view as UIView!
        let secondVCView = self.destination.view as UIView!

        // Get the screen width and height.
        let screenWidth = UIScreen.main.bounds.size.width
        let screenHeight = UIScreen.main.bounds.size.height

        // Specify the initial position of the destination view.
        secondVCView?.frame = CGRect(x: 0.0, y: screenHeight, width: screenWidth, height: screenHeight)

        // Access the app's key window and insert the destination view above the current (source) one.
        let window = UIApplication.shared.keyWindow
        window?.insertSubview(secondVCView!, aboveSubview: firstVCView!)

        // Animate the transition.
        UIView.animate(withDuration: 0.4, animations: { () -> Void in
            firstVCView?.frame = (firstVCView?.frame.offsetBy(dx: 0.0, dy: -screenHeight))!
            secondVCView?.frame = (secondVCView?.frame.offsetBy(dx: 0.0, dy: -screenHeight))!
        }, completion: { (Finished) -> Void in
            self.source.present(self.destination as UIViewController, animated: false, completion: nil)
        })
    }
}