ios - draw() 的 Swift 回调函数？

Question

我有一个 customView，我在其中覆盖了 drawRect: .我也有一些情况，我想在我的 customView 上显示一个 UILabel:

if self.ticks.count < 50 {
    self.label.frame = self.bounds
    self.label.text = "This chart requires 50 or more ticks.\nKeep Ticking."
    self.addSubview(label)
}

但是，如果我在 drawRect 之前调用此代码被调用，那么我的标签就不会出现。有没有类似viewDidDraw之类的回调方法？

编辑

有人要求它，所以这里是所有正在做我需要它做的事情的代码。我认为问题的答案是覆盖 layoutSubviews。

@IBDesignable open class  CustomView: UIView {
    @objc open var ticks:[Tick] = []
    let label = UILabel()

    required public init?(coder: NSCoder) {
        super.init(coder: coder)
        setup()
    }
    required public override init(frame: CGRect) {
        super.init(frame: frame)
        setup()
    }
    func setup(){
        self.backgroundColor = UIColor.clear
        self.label.frame = self.bounds
        self.label.text = "This chart requires 50 or more ticks.\nKeep Ticking."
        self.label.numberOfLines = 0
        self.label.textAlignment = .center
        self.addSubview(label)
    }

    override open func layoutSubviews() {
        self.label.frame = self.bounds
    }

    @objc open func setSessions(sessions:[Session]){
        self.ticks = []
        for session in sessions.reversed(){
            if self.ticks.count < 250{
                self.ticks = self.ticks + (session.getShots() as! [Shot])
            }else{
                break
            }
        }
        if self.ticks.count < 50 {
            self.label.isHidden = false
        }else{
            self.label.isHidden = true
        }
        self.bringSubview(toFront: self.label)
    }

    override open func draw(_ rect: CGRect) {
        let context = UIGraphicsGetCurrentContext()!
        let width = rect.width - 10;
        let height = rect.height - 10;
        let center = CGPoint(x: width/2+5, y: height/2+5)
        let big_r = min(width, height)/2

        context.setLineWidth(1.5)
        UIColor.white.setStroke()

        //draw the rings
        for i in stride(from: 1, to: 7, by: 1){
            let r = big_r * CGFloat(i) / 6.0;
            context.addArc(center:center, radius:r, startAngle: 0, endAngle: CGFloat(2*Double.pi), clockwise: false)
            context.strokePath()
        }

        //draw the ticks
        if self.ticks.count > 49 {
            UIColor.red().setFill()
            for (i, tick) in self.ticks.prefix(250).enumerated(){
                let radius = min((100.0-CGFloat(shot.score))/30.0 * big_r, big_r);

                let x = Utilities.calculateX(tick, radius)
                let y = Utilities.calculateY(tick, radius)

                let point = CGPoint(x: x+center.x,y: y+center.y)
                context.addArc(center:point, radius:CGFloat(DOT_WIDTH/2), startAngle: 0, endAngle: CGFloat(2*Double.pi), clockwise: false)
                context.fillPath()
            }
        }
    }
}

Answer 1

您可以在需要时通过调用 setNeedsDisplay() 来重绘自定义 View 。之后，您可以添加标签