如何在 iOS swift 中的 UIButton 上设置渐变？

Question

我有一个 UIButton。我想设置按钮的渐变如下。

我尝试了下面的代码，但它没有按照屏幕截图设置颜色。

 func applyGradient(colours: [UIColor]) -> Void {
        self.applyGradient(colours: colours, locations: nil)
    }

    func applyGradient(colours: [UIColor], locations: [NSNumber]?) -> Void {
        let gradient: CAGradientLayer = CAGradientLayer()
        gradient.frame = self.bounds
        gradient.colors = colours.map { $0.cgColor }
        gradient.locations = locations
        self.layer.insertSublayer(gradient, at: 0)
    }

Answer 1

你可以简单地这样做：

extension UIButton
{
    func applyGradient(colors: [CGColor])
    {
        let gradientLayer = CAGradientLayer()
        gradientLayer.colors = colors
        gradientLayer.startPoint = CGPoint(x: 0, y: 0)
        gradientLayer.endPoint = CGPoint(x: 1, y: 0)
        gradientLayer.frame = self.bounds
        self.layer.insertSublayer(gradientLayer, at: 0)
    }
}

在UIButton上设置渐变：

self.button.applyGradient(colors: [UIColor.green.cgColor, UIColor.black.cgColor])

Answer 2

您可以将这个完整的扩展用于所有视图：

// MARK: - Gradient

extension UIView {

    enum axis {
        case vertical, horizontal, custom(angle: CGFloat)
    }

    func setGradientBackgroundColor(colors: [UIColor], axis: axis, cornerRadius: CGFloat? = nil, apply: ((UIView) -> ())? = nil) {
        layer.sublayers?.filter { $0.name == "gradientLayer" }.forEach { $0.removeFromSuperlayer() }
        self.layoutIfNeeded()

        let cgColors = colors.map { $0.cgColor }

        let gradient: CAGradientLayer = CAGradientLayer()
        gradient.colors = cgColors
        gradient.name = "gradientLayer"
        gradient.locations = [0.0, 1.0]

        switch axis {
            case .horizontal:
                gradient.startPoint = CGPoint(x: 0.0, y: 1.0)
                gradient.endPoint = CGPoint(x: 1.0, y: 1.0)
            case .custom(let angle):
                calculatePoints(for: angle, gradient: gradient)
            default:
                break
        }

        gradient.frame = self.bounds
        self.layer.insertSublayer(gradient, at: 0)

        guard let cornerRadius = cornerRadius else { return }

        let circularPath = CGMutablePath()

        circularPath.move(to: CGPoint.init(x: cornerRadius, y: 0))
        circularPath.addLine(to: CGPoint.init(x: self.bounds.width - cornerRadius, y: 0))
        circularPath.addQuadCurve(to: CGPoint.init(x: self.bounds.width, y: cornerRadius), control: CGPoint.init(x: self.bounds.width, y: 0))
        circularPath.addLine(to: CGPoint.init(x: self.bounds.width, y: self.bounds.height - cornerRadius))
        circularPath.addQuadCurve(to: CGPoint.init(x: self.bounds.width - cornerRadius, y: self.bounds.height), control: CGPoint.init(x: self.bounds.width, y: self.bounds.height))
        circularPath.addLine(to: CGPoint.init(x: cornerRadius, y: self.bounds.height))
        circularPath.addQuadCurve(to: CGPoint.init(x: 0, y: self.bounds.height - cornerRadius), control: CGPoint.init(x: 0, y: self.bounds.height))
        circularPath.addLine(to: CGPoint.init(x: 0, y: cornerRadius))
        circularPath.addQuadCurve(to: CGPoint.init(x: cornerRadius, y: 0), control: CGPoint.init(x: 0, y: 0))


        let maskLayer = CAShapeLayer()
        maskLayer.path = circularPath
        maskLayer.fillRule = CAShapeLayerFillRule.evenOdd
        maskLayer.fillColor = UIColor.red.cgColor
        self.layer.mask = maskLayer

        apply?(self)
    }

    func calculatePoints(for angle: CGFloat, gradient: CAGradientLayer) {

        var ang = (-angle).truncatingRemainder(dividingBy: 360)
        if ang < 0 { ang = 360 + ang }
        let n: CGFloat = 0.5

        switch ang {
            case 0...45, 315...360:
                let a = CGPoint(x: 0, y: n * tanx(ang) + n)
                let b = CGPoint(x: 1, y: n * tanx(-ang) + n)
                gradient.startPoint = a
                gradient.endPoint = b
            case 45...135:
                let a = CGPoint(x: n * tanx(ang - 90) + n, y: 1)
                let b = CGPoint(x: n * tanx(-ang - 90) + n, y: 0)
                gradient.startPoint = a
                gradient.endPoint = b
            case 135...225:
                let a = CGPoint(x: 1, y: n * tanx(-ang) + n)
                let b = CGPoint(x: 0, y: n * tanx(ang) + n)
                gradient.startPoint = a
                gradient.endPoint = b
            case 225...315:
                let a = CGPoint(x: n * tanx(-ang - 90) + n, y: 0)
                let b = CGPoint(x: n * tanx(ang - 90) + n, y: 1)
                gradient.startPoint = a
                gradient.endPoint = b
            default:
                let a = CGPoint(x: 0, y: n)
                let b = CGPoint(x: 1, y: n)
                gradient.startPoint = a
                gradient.endPoint = b

        }
    }

    private func tanx(_ ?: CGFloat) -> CGFloat {
        return tan(? * CGFloat.pi / 180)
    }

}

使用：

btn.setGradientBackgroundColor(colors: [.softBlue, .seaBlue], axis: .horizontal, cornerRadius: 5) { view in
            guard let btn = view as? UIButton, let imageView = btn.imageView else { return }
            btn.bringSubviewToFront(imageView) // To display imageview of button
        }

Answer 3

上面的代码对我有用，创建扩展很好，因为渐变可以应用于多个按钮

如果需要为渐变添加圆角半径，只需在上面的代码中添加一行代码

extension UIButton
{
    func applyGradient(colors: [CGColor])
    {
        let gradientLayer = CAGradientLayer()
        gradientLayer.colors = colors
        gradientLayer.startPoint = CGPoint(x: 0, y: 0)
        gradientLayer.endPoint = CGPoint(x: 1, y: 0)
        gradientLayer.frame = self.bounds
        gradientLayer.cornerRadius = self.frame.size.height / 2
        self.layer.insertSublayer(gradientLayer, at: 0)
    }
}