ios - iOS 中的自定义 View 和自定义按钮

Question

我创建了两个自定义类:CutomView 类(UIView 的子类)和 CustomButton 类(UIButton 的子类)。

class CustomView: UIView {

    override func drawRect(rect: CGRect) {
        // Drawing code
        layer.masksToBounds = true
        layer.borderWidth = 2.0
        layer.borderColor = UIColor(colorLiteralRed: 0.0/255, green: 64.0/255, blue: 128.0/255, alpha: 1).CGColor
        layer.cornerRadius = 10.0
        let startColor = UIColor(colorLiteralRed: 255.0/255, green: 204.0/255, blue: 1.0, alpha: 1.0).CGColor
        let endColor = UIColor(colorLiteralRed: 0, green: 128.0/255, blue: 1.0, alpha: 1.0).CGColor
        let gradientLayer = CAGradientLayer()
        gradientLayer.frame = CGRect(origin: layer.frame.origin, size: layer.frame.size)
        gradientLayer.colors = [startColor, endColor];
        layer.addSublayer(gradientLayer)
    }

和

@IBDesignable
class CustomButton: UIButton {
    override func drawRect(rect: CGRect) {
        // Drawing code
        layer.masksToBounds = true
        layer.borderWidth = 2.0
        layer.borderColor = UIColor(colorLiteralRed: 0.0/255, green: 64.0/255, blue: 128.0/255, alpha: 1).CGColor
        layer.cornerRadius = 2.0
        let startColor = UIColor(colorLiteralRed: 192.0/255, green: 192.0/255, blue: 192.0/255, alpha: 1.0).CGColor
        let endColor = UIColor(colorLiteralRed: 239.0/255, green: 239.0/255, blue: 239.0/255, alpha: 1.0).CGColor
        let gradientLayer = CAGradientLayer()
        gradientLayer.frame = CGRect(origin: layer.frame.origin, size: layer.frame.size)
        gradientLayer.colors = [startColor, endColor];
        layer.addSublayer(gradientLayer)
    }

}

我使用这些自定义子类来设计 View 和按钮。当我查看应用的自定义类时，它们工作正常，但由于某些原因，该按钮在模拟器或 iOS 设备中不可见。

如果有人能指出我的错误或帮助我修复它，那就太好了。

Storyboard and Preview shows the purple blue background and button

Simulator only displays purple blue background

Answer 1

您的layer.addSublayer调用将图层附加到您的图层层次结构中。因此，渐变是最后绘制的，有效地绘制在您的自定义按钮上。您希望渐变成为背景，因此请确保它是绘制的第一层。改变

layer.addSublayer(gradientLayer)

至

layer.insertSublayer(gradientLayer, atIndex: 0)