How to add slide to unlock effect to a UITextView or UILabel?

Question

I have a large text and want to add an effect that is similar to the slide to unlock one of the latest iOS and that will go from top to bottom with the text sliding from bottom to top.

Answer 1

Update with swift shimmering label, view etc...

import UIKit
import QuartzCore

class ViewController: UIViewController {

    @IBOutlet var testLabel: UILabel!

    override func viewDidLoad() {
        super.viewDidLoad()
        self.testLabel.startShimmering()
    }
}

extension UIView {
    func startShimmering() {
        //        let light = UIColor.init(white: 0, alpha: 0.1).cgColor
        let light = UIColor(red: 0, green: 0, blue: 0, alpha: 0.1).cgColor
        let dark = UIColor.black.cgColor

        let gradient: CAGradientLayer = CAGradientLayer()
        gradient.colors = [dark, light, dark]
        gradient.frame = CGRect(x: -self.bounds.size.width, y: 0, width: 3*self.bounds.size.width, height: self.bounds.size.height)
        gradient.startPoint = CGPoint(x: 0.0, y: 0.5)
        gradient.endPoint = CGPoint(x: 1.0, y: 0.525)
        gradient.locations = [0.4, 0.5, 0.6]
        self.layer.mask = gradient

        let animation: CABasicAnimation = CABasicAnimation(keyPath: "locations")
        animation.fromValue = [0.0, 0.1, 0.2]
        animation.toValue = [0.8, 0.9, 1.0]

        animation.duration = 1.5
        animation.repeatCount = HUGE
        gradient.add(animation, forKey: "shimmer")


    }

    func stopShimmering() {
        self.layer.mask = nil
    }

}

Answer 2

I suggest you use Grant Pauls's Shimmer control, because it does just that.

https://github.com/facebook/Shimmer