CAGradientLayer渐变色效果

        let gradientLayer = CAGradientLayer()
        gradientLayer.frame = YHRect
        let color1 = UIColor(white: 0.5, alpha: 0.2).cgColor
        let color2 = UIColor(red: 1.0, green: 0, blue: 0, alpha: 0.4).cgColor
        let color3 = UIColor(red: 0, green: 1, blue: 0, alpha: 0.3).cgColor
        let color4 = UIColor(red: 0, green: 0, blue: 1, alpha: 0.3).cgColor
        let color5 = UIColor(white: 0.4, alpha: 0.2).cgColor
        
        gradientLayer.colors = [color1, color2, color3, color4, color5]
        gradientLayer.locations = [0.10, 0.30, 0.50, 0.70, 0.90]
        gradientLayer.startPoint = CGPoint(x: 0, y: 0)
        gradientLayer.endPoint = CGPoint(x: 1, y: 1)
        view.layer.addSublayer(gradientLayer)

<li><h1>学习代码:<h1></li>

ViewController.swift

import UIKit

let YHRect = UIScreen.main.bounds
let YHHeight = YHRect.size.height
let YHWidth = YHRect.size.width

class ViewController: UIViewController {
    
    let gradientLayer = CAGradientLayer()

    override func viewDidLoad() {
        super.viewDidLoad()
        setupView()
    }
    
    override var preferredStatusBarStyle: UIStatusBarStyle {
        return .lightContent
    }
    
    func setupView() {
        setupGradientLayer()
        Timer.scheduledTimer(timeInterval: 1, target: self, selector: #selector(randomColor), userInfo: nil, repeats: true)
        
    }
    func setupGradientLayer() {
        gradientLayer.frame = YHRect
        let color1 = UIColor(white: 0.5, alpha: 0.2).cgColor
        let color2 = UIColor(red: 1.0, green: 0, blue: 0, alpha: 0.4).cgColor
        let color3 = UIColor(red: 0, green: 1, blue: 0, alpha: 0.3).cgColor
        let color4 = UIColor(red: 0, green: 0, blue: 1, alpha: 0.3).cgColor
        let color5 = UIColor(white: 0.4, alpha: 0.2).cgColor
        
        gradientLayer.colors = [color1, color2, color3, color4, color5]
        gradientLayer.locations = [0.10, 0.30, 0.50, 0.70, 0.90]
        gradientLayer.startPoint = CGPoint(x: 0, y: 0)
        gradientLayer.endPoint = CGPoint(x: 1, y: 1)
        view.layer.addSublayer(gradientLayer)
    }
    func randomColor() {
        view.backgroundColor = UIColor(red: CGFloat(drand48()), green: CGFloat(drand48()), blue: CGFloat(drand48()), alpha: 1.0)
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }


}