A simple view to animate in and out a blurry overlay. Use .blurIn() and .blurOut() to animate the blur. User interaction is passed through when the view is not blurry. NOTE: If you use storyboards, you need to drag out a UIVisualEffectView and set the class. It doesn't work if you drag out a plain old UIView.

BlurryOverlayView.swift

class BlurryOverlayView: UIVisualEffectView {
    private var animator: UIViewPropertyAnimator!
    private var delta: CGFloat = 0 // The amount to change fractionComplete for each tick
    private var target: CGFloat = 0 // The fractionComplete we're animating to
    private(set) var isBlurred = false
    private var displayLink: CADisplayLink!
    
    override init(effect: UIVisualEffect?) {
        super.init(effect: effect)
        setup()
    }
    
    required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
        setup()
    }
    
    // Common init
    private func setup() {
        effect = nil // Starts out with no blur
        isHidden = true // Enables user interaction through the view
        
        // The animation to add an effect
        animator = UIViewPropertyAnimator(duration: 1, curve: .easeInOut) {
            self.effect = UIBlurEffect(style: .light)
        }
        animator.pausesOnCompletion = true // Fixes background bug
        
        // Using a display link to animate animator.fractionComplete
        displayLink = CADisplayLink(target: self, selector: #selector(tick))
        displayLink.isPaused = true
        displayLink.add(to: .main, forMode: .commonModes)
    }
    
    func blurIn(amount: CGFloat = 0.2, duration: TimeInterval = 0.3) {
        guard isBlurred == false else { return }
        
        isHidden = false // Disable user interaction
        
        target = amount
        delta = amount / (60 * CGFloat(duration)) // Assuming 60hz refresh rate
        
        // Start animating fractionComplete
        displayLink.isPaused = false
    }
    
    func blurOut(duration: TimeInterval = 0.3) {
        guard isBlurred else { return }
        
        target = 0
        delta = -1 * animator.fractionComplete / (60 * CGFloat(duration)) // Assuming 60hz refresh rate
        
        // Start animating fractionComplete
        displayLink.isPaused = false
    }
    
    @objc private func tick() {
        animator.fractionComplete += delta
        
        if isBlurred && animator.fractionComplete <= 0 {
            // Done blurring out
            isBlurred = false
            isHidden = true
            displayLink.isPaused = true
        } else if isBlurred == false && animator.fractionComplete >= target {
            // Done blurring in
            isBlurred = true
            displayLink.isPaused = true
        }
    }
}

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