Shimmering views

UIView+Shimmer.swift

//
//  UIView+Shimmer.swift
//  SearchFlights
//
//  Created by Jessy Hanzo on 16/05/2019.
//  Copyright © 2019 jho. All rights reserved.
//

import Foundation
import UIKit

// inspired by https://github.com/AjayBhanushali/ABLoaderView

extension UIView {
    public func startShimmering() {
        self.layoutIfNeeded()
        self.animate()
    }

    public func stopShimmering() {
        self.layoutIfNeeded()
        let layers = self.layer.sublayers?.filter({$0.name == "colorLayer" || $0.name == "loaderLayer"})
        layers?.forEach { $0.removeFromSuperlayer() }
    }

    private func animate() {
        // Add Color Layer
        let colorLayer = CALayer()
        colorLayer.backgroundColor = UIColor(white: 0.82, alpha: 1).cgColor
        colorLayer.frame = CGRect(x: 0, y: 0, width: self.bounds.width, height: self.bounds.height)
        colorLayer.name = "colorLayer"
        self.layer.addSublayer(colorLayer)
        self.autoresizesSubviews = true
        self.clipsToBounds = true
        
        // Add loader Layer
        let gradientLayer = CAGradientLayer()
        gradientLayer.colors = [
            UIColor(white: 0.82, alpha: 1).cgColor,
            UIColor(white: 0.86, alpha: 1).cgColor,
            UIColor(white: 0.82, alpha: 1).cgColor
        ]
        gradientLayer.locations = [0,0.4,0.8, 1]
        gradientLayer.name = "loaderLayer"
        gradientLayer.startPoint = CGPoint(x: 0.0, y: 0.5)
        gradientLayer.endPoint = CGPoint(x: 1.0, y: 0.5)
        gradientLayer.frame = CGRect(x: 0, y: 0, width: self.bounds.width, height: self.bounds.height)
        self.layer.addSublayer(gradientLayer)
        
        // Animate loader layer
        let animation = CABasicAnimation(keyPath: "transform.translation.x")
        animation.duration = 1.2
        animation.fromValue = -self.frame.width
        animation.toValue = self.frame.width
        animation.repeatCount = Float.infinity
        gradientLayer.add(animation, forKey: "smartLoader")
    }
}