在iOS中显示前添加按钮渐变

import UIKit

class ViewController: UIViewController {
    override func viewDidLoad() {
        super.viewDidLoad()
        
        // 创建按钮
        let button = UIButton(type: .system)
        button.frame = CGRect(x: 100, y: 100, width: 200, height: 50)
        button.setTitle("按钮", for: .normal)
        
        // 创建渐变层
        let gradientLayer = CAGradientLayer()
        gradientLayer.frame = button.bounds
        gradientLayer.colors = [UIColor.red.cgColor, UIColor.blue.cgColor]
        gradientLayer.startPoint = CGPoint(x: 0, y: 0)
        gradientLayer.endPoint = CGPoint(x: 1, y: 0)
        
        // 添加渐变层到按钮的layer层
        button.layer.addSublayer(gradientLayer)
        
        // 将按钮添加到视图中
        view.addSubview(button)
    }
}