如何将UIView的背景颜色快速设置为渐变颜色？

Question

我正在尝试使用以下代码迅速将按钮和标签的颜色设置为渐变颜色：

extension UIView {

    func setGradientColor(colorOne: UIColor, colorTwo: UIColor) {

        let gradientLayer = CAGradientLayer()
        gradientLayer.frame = bounds
        gradientLayer.colors = [colorOne.cgColor, colorTwo.cgColor]
        gradientLayer.locations = [0.0,0.1]
        gradientLayer.startPoint = CGPoint(x: 1.0, y: 1.0)
        gradientLayer.endPoint = CGPoint(x: 0.0, y: 0.0)

        layer.insertSublayer(gradientLayer, at: 0)
   }
}

然后在登录表单中，我使用如下扩展名：

let logo: UILabel = {
    let logo = UILabel()
    logo.text = "Logo"
    logo.setGradientColor(colorOne: UIColor.blue, colorTwo: UIColor.yellow)
    logo.textAlignment = .center
    logo.font = UIFont.boldSystemFont(ofSize: 59)
    return logo
}()

但它仍然显示为黑色。我该如何解决？

Answer 1

您发布的内容我将...设置为徽标视图的框架或约束后，我打电话给... setGradietColor(colorOne: UIColor.blue, colorTwo: UIColor.yellow)

您可以在视图中添加渐变层

let gradient: CAGradientLayer = CAGradientLayer()

        gradient.colors = [UIColor.black.cgColor, UIColor.blue.cgColor]
        gradient.locations = [0.0 , 1.0]
        gradient.startPoint = CGPoint(x : 0.0, y : 0)
        gradient.endPoint = CGPoint(x :0.0, y: 0.5) // you need to play with 0.15 to adjust gradient vertically
        gradient.frame = view.bounds
        view.layer.addSublayer(gradient)

Answer 2

您正面临此问题，因为当frame的gradientLayer更新时您没有更新bounds的logo。例如，如果您可以引用gradientLayer，则可以在ViewController中提供此代码。

class ViewController: UIViewController {

    var gradient: CAGradientLayer?

    let logo: UILabel = {
        let logo = UILabel()
        logo.text = "Logo"
        gradient = logo.setGradietColor(colorOne: UIColor.blue, colorTwo: UIColor.yellow)
        logo.textAlignment = .center
        logo.font = UIFont.boldSystemFont(ofSize: 59)
        return logo
    }()

    override func viewDidLayoutSubviews() {
        super.viewDidLayoutSubviews()
        gradient?.frame = logo.bounds
    }
}

尝试从方法中返回layer并按如下所示修改函数：

extension UIView {

    @discardableResult
    func setGradietColor(colorOne: UIColor, colorTwo: UIColor) {

        let gradientLayer = CAGradientLayer()
        gradientLayer.frame = bounds
        gradientLayer.colors = [colorOne.cgColor, colorTwo.cgColor]
        gradientLayer.locations = [0.0,0.1]
        gradientLayer.startPoint = CGPoint(x: 1.0, y: 1.0)
        gradientLayer.endPoint = CGPoint(x: 0.0, y: 0.0)

        layer.insertSublayer(gradientLayer, at: 0)
        return layer
   }
}