下面是Swift中的一种方法，使用UIButton扩展来添加IBInspectable，称为highlightedBackgroundColor。类似于子类化，但不需要子类。

private var HighlightedBackgroundColorKey = 0
private var NormalBackgroundColorKey = 0

extension UIButton {

    @IBInspectable var highlightedBackgroundColor: UIColor? {
        get {
            return objc_getAssociatedObject(self, &HighlightedBackgroundColorKey) as? UIColor
        }

        set(newValue) {
            objc_setAssociatedObject(self,
                &HighlightedBackgroundColorKey, newValue, UInt(OBJC_ASSOCIATION_RETAIN))
        }
    }

    private var normalBackgroundColor: UIColor? {
        get {
            return objc_getAssociatedObject(self, &NormalBackgroundColorKey) as? UIColor
        }

        set(newValue) {
            objc_setAssociatedObject(self,
                &NormalBackgroundColorKey, newValue, UInt(OBJC_ASSOCIATION_RETAIN))
        }
    }

    override public var backgroundColor: UIColor? {
        didSet {
            if !highlighted {
                normalBackgroundColor = backgroundColor
            }
        }
    }

    override public var highlighted: Bool {
        didSet {
            if let highlightedBackgroundColor = self.highlightedBackgroundColor {
                if highlighted {
                    backgroundColor = highlightedBackgroundColor
                } else {
                    backgroundColor = normalBackgroundColor
                }
            }
        }
    }
}

我希望这能有所帮助。

细节

Xcode 11.1 (11A1027)， Swift 5

解决方案

import UIKit

extension UIColor {
    func createOnePixelImage() -> UIImage? {
        let size = CGSize(width: 1, height: 1)
        UIGraphicsBeginImageContext(size)
        defer { UIGraphicsEndImageContext() }
        guard let context = UIGraphicsGetCurrentContext() else { return nil }
        context.setFillColor(cgColor)
        context.fill(CGRect(origin: .zero, size: size))
        return UIGraphicsGetImageFromCurrentImageContext()
    }
}

extension UIButton {
    func setBackground(_ color: UIColor, for state: UIControl.State) {
        setBackgroundImage(color.createOnePixelImage(), for: state)
    }
}

使用

button.setBackground(.green, for: .normal)

Swift中一个方便的通用扩展:

extension UIButton {
    private func imageWithColor(color: UIColor) -> UIImage {
        let rect = CGRectMake(0.0, 0.0, 1.0, 1.0)
        UIGraphicsBeginImageContext(rect.size)
        let context = UIGraphicsGetCurrentContext()

        CGContextSetFillColorWithColor(context, color.CGColor)
        CGContextFillRect(context, rect)

        let image = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()

        return image
    }

    func setBackgroundColor(color: UIColor, forUIControlState state: UIControlState) {
        self.setBackgroundImage(imageWithColor(color), forState: state)
    }
}

斯威夫特3.0

extension UIButton {
    private func imageWithColor(color: UIColor) -> UIImage? {
        let rect = CGRect(x: 0.0, y: 0.0, width: 1.0, height: 1.0)
        UIGraphicsBeginImageContext(rect.size)
        let context = UIGraphicsGetCurrentContext()

        context?.setFillColor(color.cgColor)
        context?.fill(rect)

        let image = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()

        return image
    }

    func setBackgroundColor(_ color: UIColor, for state: UIControlState) {
        self.setBackgroundImage(imageWithColor(color: color), for: state)
    }
}

不需要重写高亮显示为computed属性。你可以使用属性观察者来触发背景颜色的变化:

override var highlighted: Bool {
    didSet {
        backgroundColor = highlighted ? UIColor.lightGrayColor() : UIColor.whiteColor()
    }
}

斯威夫特4

override open var isHighlighted: Bool {
    didSet {
        backgroundColor = isHighlighted ? UIColor.lightGray : UIColor.white
    }
}

下面是Swift中选择按钮状态的代码:

func imageWithColor(color:UIColor) -> UIImage {
    let rect:CGRect = CGRectMake(0.0, 0.0, 1.0, 1.0)
     UIGraphicsBeginImageContext(rect.size)
    let context:CGContextRef = UIGraphicsGetCurrentContext()!
    CGContextSetFillColorWithColor(context, color.CGColor)
    CGContextFillRect(context, rect)
    let image:UIImage = UIGraphicsGetImageFromCurrentImageContext();
    return image;
}

例子:

    self.button.setImage(self.imageWithColor(UIColor.blackColor()), forState: .Highlighted)

extension UIButton {
    func setBackgroundColor(color: UIColor, forState: UIControl.State) {
        let size = CGSize(width: 1, height: 1)
        UIGraphicsBeginImageContext(size)
        let context = UIGraphicsGetCurrentContext()
        context?.setFillColor(color.cgColor)
        context?.fill(CGRect(origin: CGPoint.zero, size: size))
        let colorImage = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()
        setBackgroundImage(colorImage, for: forState)
    }

}

谢谢@Maverick