CAShapeLayer 在 XIB 中不可见 swift iOS

Question

我正在使用 XIB 文件构建自定义视图。但是，我遇到了一个问题，我添加到视图 (trackLayer) 的层没有显示在 xib 上（circleLayer 是一个动画，我不希望它在 xib 中呈现，据我所知这是不可能的）。 XIB的所有者class代码如下：

@IBDesignable
class SpinningView: UIView {

@IBOutlet var contentView: SpinningView!

//MARK: Properties
let circleLayer = CAShapeLayer()
let trackLayer = CAShapeLayer()

let circularAnimation: CABasicAnimation = {
    let animation = CABasicAnimation()
    animation.fromValue = 0
    animation.toValue = 1
    animation.duration = 2
    animation.fillMode = kCAFillModeForwards
    animation.isRemovedOnCompletion = false
    return animation
}()

//MARK: IB Inspectables
@IBInspectable var strokeColor: UIColor = UIColor.red {
    ...
}

@IBInspectable var trackColor: UIColor = UIColor.lightGray {
    ...
}

@IBInspectable var lineWidth: CGFloat = 5 {
    ...
}

@IBInspectable var fillColor: UIColor = UIColor.clear {
    ...
}

@IBInspectable var isAnimated: Bool = true {
    ...
}

//MARK: Initialization
override init(frame: CGRect) {
    super.init(frame: frame)
    initSubviews()
}

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

    setup()
    initSubviews()
}

//MARK: Private functions
private func setup() {
    setupTrack()
    setupAnimationOnTrack()
}

private func setupTrack(){
    trackLayer.lineWidth = lineWidth
    trackLayer.fillColor = fillColor.cgColor
    trackLayer.strokeColor = trackColor.cgColor
    layer.addSublayer(trackLayer)
}

private func setupAnimationOnTrack(){
    circleLayer.lineWidth = lineWidth
    circleLayer.fillColor = fillColor.cgColor
    circleLayer.strokeColor = strokeColor.cgColor
    circleLayer.lineCap = kCALineCapRound
    layer.addSublayer(circleLayer)
    updateAnimation()
}

private func updateAnimation() {
    if isAnimated {
        circleLayer.add(circularAnimation, forKey: "strokeEnd")
    }
    else {
        circleLayer.removeAnimation(forKey: "strokeEnd")
    }
}

//MARK: Layout contraints
override func layoutSubviews() {
    super.layoutSubviews()

    let center = CGPoint(x: bounds.midX, y: bounds.midY)
    let radius = min(bounds.width / 2, bounds.height / 2) - circleLayer.lineWidth / 2

    let startAngle = -CGFloat.pi / 2
    let endAngle = 3 * CGFloat.pi / 2
    let path = UIBezierPath(arcCenter: .zero, radius: radius, startAngle: startAngle, endAngle: endAngle, clockwise: true)

    trackLayer.position = center
    trackLayer.path = path.cgPath

    circleLayer.position = center
    circleLayer.path = path.cgPath
}

private func initSubviews() {
    let bundle = Bundle(for: SpinningView.self)
    let nib = UINib(nibName: "SpinningView", bundle: bundle)
    nib.instantiate(withOwner: self, options: nil)
    contentView.frame = bounds
    addSubview(contentView)
}
}

当视图在 Main.storyboard 中被子class 编辑时，我可以看到如下图像和轨道层 IB UIView but when I go over to the XIB, it does not have the trackLayer(circle around the image) XIB Image。虽然有人会争辩说它正在工作以及为什么我为此烦恼，但我认为正确设计 XIB 很重要，因为另一个人可能只是将它视为只有图像的视图（不知道动画功能）

Answer 1

当您设计 XIB 时，它不是您的 @IBDesignable SpinningView 的 实例。实际上，您正在查看 SpinningView.

的 source
因此，它背后的代码此时不是运行 - 它仅在您将 SpinningView 的实例添加到另一个视图时运行。

看看这个简单的例子：

@IBDesignable class SpinningView: UIView { @IBOutlet var contentView: UIView! @IBOutlet var theLabel: UILabel! //MARK: Initialization override init(frame: CGRect) { super.init(frame: frame) initSubviews() } required init?(coder aDecoder: NSCoder) { super.init(coder: aDecoder) initSubviews() } private func initSubviews() { let bundle = Bundle(for: SpinningView.self) let nib = UINib(nibName: "SpinningView", bundle: bundle) nib.instantiate(withOwner: self, options: nil) contentView.frame = bounds addSubview(contentView) // this will change the label's textColor in Storyboard // when a UIView's class is set to SpinningView theLabel.textColor = .red } }

当我设计 XIB 时，这是我看到的：

但是当我将 UIView 添加到另一个视图，并将其 class 分配为 SpinningView 时，我看到的是：

标签的文本颜色更改为红色，因为代码现在是运行。

另一种思考方式...您将 trackColor、fillColor 等变量定义为 @IBInspectable。当您设计 XIB 时，您不会在 Xcode 的属性检查器面板中看到这些属性 - 只有当您选择了已添加到其他地方的 SpinningView 实例时才会看到它们。

希望这是有道理的。

CAShapeLayer 在 XIB 中不可见 swift iOS

CAShapeLayer not visible in XIB swift iOS

interface-builder

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swift