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How to animate a blur effect using UIVisualEffectView

Written by Paul Hudson    @twostraws

UIKit’s UIVisualEffectView class lets us add blurring effects to any view, optionally also combining a vibrancy effect to overlaid controls to help make them stand out. This makes it perfect for partly obscuring background content when you want to present information on top, and you can even animate that presentation if you want.

First, place a UIVisualEffectView into your view controller, either using code or using IB with an outlet.

When your app launches you should clear the effect property of your visual effect view, causing it to do nothing:

visualEffectView.effect = nil

When you want the blur to animate in – i.e., when you’re ready to show information on top – just set that effect property to a new instance of UIBlurEffect inside an animation block, like this:

UIView.animate(withDuration: 5) {
    self.visualEffectView.effect = UIBlurEffect(style: UIBlurEffectStyle.prominent)
}

UIKit will take care of the rest!

Available from iOS 7.0

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