ios - 画(_直角: CGRect) not getting called in custom view

Question

我正在尝试通过扩展类 UIView 来创建自定义 View ，该类可以在自定义 View 的中心显示一个圆圈。为了添加自定义绘图，我重写了 draw(_ rect: CGRect) 方法，如下所示。

    public override func draw(_ rect: CGRect) {
        super.draw(rect)
        let center = CGPoint(x: bounds.width / 2, y: bounds.height / 2)
        let minLength = bounds.width <= bounds.height ? bounds.width : bounds.height
        let circlePath = UIBezierPath (arcCenter: center, radius: CGFloat(minLength  / 2), startAngle: 0, endAngle: CGFloat(Float(360).degreesToRadians) , clockwise: true)

        let shapeLayer = CAShapeLayer()
        shapeLayer.path = circlePath.cgPath
        shapeLayer.fillColor = circleColor.cgColor
        layer.addSublayer(shapeLayer)
    }

但是当我尝试在 Storyboard 中添加相同的自定义组件并在 draw 方法中添加断点时，它没有被调用。出于好奇，我在被调用的 init?(coder aDecoder: NSCoder) 方法中添加了一个断点。此外，当我尝试如下重写该方法时，它工作正常。

required public init?(coder aDecoder: NSCoder) {
    super.init(coder: aDecoder)
    drawCircle()
}

fileprivate func drawCircle() {
    let center = CGPoint(x: bounds.width / 2, y: bounds.height / 2)
    let minLength = bounds.width <= bounds.height ? bounds.width : bounds.height
    let circlePath = UIBezierPath (arcCenter: center, radius: CGFloat(minLength  / 2), startAngle: 0, endAngle: CGFloat(Float(360).degreesToRadians) , clockwise: true)

    let shapeLayer = CAShapeLayer()
    shapeLayer.path = circlePath.cgPath
    shapeLayer.fillColor = circleColor.cgColor

    layer.addSublayer(shapeLayer)
}

方法的问题是我有一个自定义属性 circleColor

@IBInspectable
public var circleColor : UIColor = UIColor.gray

在调用init方法时还没有设置，它总是画一个灰色的圆圈。

请帮助让我知道未调用 draw 方法的原因。

提前致谢

Answer 1

我不确定你的根本错误在哪里，但你不应该为了添加一个层而覆盖 draw(:)。这意味着每次组件重新渲染时都会再次添加一个新层。这不是你想要的。

您还应该确保在更改颜色属性时更新图层颜色。为此，只需保存对图层的引用:

private let shapeLayer = CAShapeLayer()

@IBInspectable
public var circleColor : UIColor = UIColor.gray  {
   didSet {
      shapeLayer.fillColor = circleColor.cgColor
   }
}

public override init(frame: CGRect = .zero) {
    super.init(frame: frame)
    updateLayer()
    layer.addSublayer(shapeLayer)
}

required public init?(coder aDecoder: NSCoder) {
    super.init(coder: aDecoder)
    updateLayer()
    layer.addSublayer(shapeLayer)
}

fileprivate func updateLayer() {
    let center = CGPoint(x: bounds.width / 2, y: bounds.height / 2)
    let minLength = min(bounds.width, bounds.height)
    let circlePath = UIBezierPath(arcCenter: center, radius: minLength / 2, startAngle: 0, endAngle: CGFloat(Float(360).degreesToRadians), clockwise: true)

    shapeLayer.path = circlePath.cgPath
    shapeLayer.fillColor = circleColor.cgColor
}

override func layoutSubviews() {
    super.layoutSubviews()
    // update layer position
    updateLayer()
}

如果你真的想覆盖draw(rect:)，你根本不需要创建层或覆盖初始值设定项:

@IBInspectable
public var circleColor : UIColor = UIColor.gray  {
   didSet {
      setNeedsDisplay()
   }
}

public override func draw(_ rect: CGRect) {
    // no need to call super.draw(rect)

    let center = CGPoint(x: bounds.width / 2, y: bounds.height / 2)
    let minLength = min(bounds.width, bounds.height)
    let circlePath = UIBezierPath(arcCenter: center, radius: minLength / 2, startAngle: 0, endAngle: .pi * 2, clockwise: true)

    // the following methods use current CGContext
    circleColor.set()
    circlePath.fill()
}