dannyYassine / MaskAnimatedTransitioning

Animator Controller for a custom transition between UIViewControllers

Mask-Animated-Transitioning (UIViewControllerAnimatedTransitioning)

Animator Controller for a custom transition between UIViewControllers

I got inspired by this post (http://iosdevtips.co/post/88481653818/twitter-ios-app-bird-zoom-animation) to create a custom transition between two UIViewControllers.

A mask is applied during the transition. The destionation UIViewController is set a mask, which is an image.

Snippet

    // Context container view
    let containerView = transitionContext.containerView()!
    
    // Destination ViewController
    toViewController = transitionContext.viewControllerForKey(UITransitionContextToViewControllerKey)
    
    // Mask
    let mask = CAShapeLayer()
    mask.contents = UIImage(named: "twitter")?.CGImage
    mask.bounds = CGRect(x: 0, y: 0, width: 100, height: 100)
    mask.anchorPoint = CGPoint(x: 0.5, y: 0.5)
    mask.position = CGPoint(x: toViewController!.view.center.x, y: toViewController!.view.center.y)
    
    // Add it in the context
    containerView.addSubview(toViewController!.view)
    
    // Apply Mask
    toViewController!.view.layer.mask = mask
    
    // Apply Animation
    // Credit to iosdevtips for this animation snippet
    let keyFrameAnimation = CAKeyframeAnimation(keyPath: "bounds")
    keyFrameAnimation.delegate = self
    keyFrameAnimation.duration = 1
    keyFrameAnimation.timingFunctions = [CAMediaTimingFunction(name: kCAMediaTimingFunctionEaseInEaseOut), CAMediaTimingFunction(name: kCAMediaTimingFunctionEaseInEaseOut)]
    let initalBounds = NSValue(CGRect: mask.bounds)
    let secondBounds = NSValue(CGRect: CGRect(x: 0, y: 0, width: 90, height: 90))
    let finalBounds = NSValue(CGRect: CGRect(x: 0, y: 0, width: 2000, height: 2000))
    keyFrameAnimation.values = [initalBounds, secondBounds, finalBounds]
    keyFrameAnimation.keyTimes = [0, 0.3, 1]
    keyFrameAnimation.removedOnCompletion = false
    keyFrameAnimation.fillMode = kCAFillModeForwards
    mask.addAnimation(keyFrameAnimation, forKey: "bounds")