UISegmentedControl TintColor в цвет градиента

Попробуйте этот код, я добавляю комментарии к соответствующим частям. Дайте мне знать, если вам нужно больше объяснений.

 let segmentedControl: UISegmentedControl = {
       let view =  UISegmentedControl(items: ["Pounds", "Kilograms"])
        view.selectedSegmentIndex = 0
        view.tintColor = .black
        view.backgroundColor = .white
        view.frame = CGRect(x: 0, y: 0, width: UIScreen.main.bounds.width - 40, height: 20)
        /// Gradient
        let gradient = CAGradientLayer()
        gradient.frame =  CGRect(x: 0, y: 0, width:  UIScreen.main.bounds.width - 40, height: 20)
        let leftColor = UIColor.red
        let rightColor = UIColor.purple
        gradient.colors = [leftColor.cgColor, rightColor.cgColor]
        gradient.startPoint = CGPoint(x: 0, y: 0.5)
        gradient.endPoint = CGPoint(x: 1.0, y: 0.5)
        /// Create gradient image
        UIGraphicsBeginImageContext(gradient.frame.size)
        gradient.render(in: UIGraphicsGetCurrentContext()!)
        let segmentedControlImage = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()

        // Normal Image
        let rect: CGRect = CGRect(x: 0, y: 0, width: 1, height: 1)
        UIGraphicsBeginImageContext(rect.size);
        let context:CGContext = UIGraphicsGetCurrentContext()!;
        context.setFillColor(UIColor.white.cgColor)
        context.fill(rect)
        let normalImage:UIImage = UIGraphicsGetImageFromCurrentImageContext()!
        UIGraphicsEndImageContext()
        /// Set segmentedControl image
        view.setBackgroundImage(normalImage, for: .normal, barMetrics: .default)
        view.setBackgroundImage(segmentedControlImage, for: .selected, barMetrics: .default)
        return view
    }()

Использование: в ViewDidLoad установите представление заголовка navigationItem в качестве сегментированного элемента управления следующим образом:

self.navigationItem.titleView = segmentedControl

   func configureSegementedControl(segmentedControl: UISegmentedControl) {
        segmentedControl.selectedSegmentIndex = 0
        segmentedControl.tintColor = .black
        segmentedControl.backgroundColor = .white
        segmentedControl.frame = CGRect(x: 0, y: 0, width: UIScreen.main.bounds.width - 40, height: 20)
        /// Gradient
        let gradient = CAGradientLayer()
        gradient.frame =  CGRect(x: 0, y: 0, width:  UIScreen.main.bounds.width - 40, height: 20)
        let leftColor = UIColor.red
        let rightColor = UIColor.purple
        gradient.colors = [leftColor.cgColor, rightColor.cgColor]
        gradient.startPoint = CGPoint(x: 0, y: 0.5)
        gradient.endPoint = CGPoint(x: 1.0, y: 0.5)
        /// Create gradient image
        UIGraphicsBeginImageContext(gradient.frame.size)
        gradient.render(in: UIGraphicsGetCurrentContext()!)
        let segmentedControlImage = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()
        // Normal Image
        let rect: CGRect = CGRect(x: 0, y: 0, width: 1, height: 1)
        UIGraphicsBeginImageContext(rect.size);
        let context:CGContext = UIGraphicsGetCurrentContext()!;
        context.setFillColor(UIColor.white.cgColor)
        context.fill(rect)
        let normalImage:UIImage = UIGraphicsGetImageFromCurrentImageContext()!
        UIGraphicsEndImageContext()
        /// Set segmentedControl image
        segmentedControl.setBackgroundImage(normalImage, for: .normal, barMetrics: .default)
        segmentedControl.setBackgroundImage(segmentedControlImage, for: .selected, barMetrics: .default)
    }