Question

这是我视图的代码。

override func draw(_ rect: CGRect) {

    let path = self.getPath()

    path.stroke()
}

func getPath() -> UIBezierPath {

    let path = UIBezierPath()

    path.lineWidth = 1
    path.lineCapStyle = .round
    path.lineJoinStyle = .round
    mainColor.setStroke()
    mainColor.setFill()
    path.move(to: CGPoint(x:0,y:0))

    path.addQuadCurve(to: endPointLeft, controlPoint: controlPointLeft)
    path.addLine(to: startPointRight)
    path.addQuadCurve(to: endPointRight, controlPoint: controlPointRight)
    path.addLine(to: startPointLeft)

    path.fill()
    path.stroke()

    return path
}

工作正常。但是有时候进入背景一段时间后，这种观点就会消失。

*****更多信息*****

ViewController中的功能具有滚动功能，可更改此视图的高度。更改高度限制后，调用self.view.layoutIfNeeded()。

Answer 1

您可以做的是在应用程序变为活动状态时重新布局子视图，如下所示，在控制器中首先添加观察者

override func viewDidLoad() {
    super.viewDidLoad()
    NotificationCenter.default.addObserver(self, selector: #selector(applicationDidBecomeActive(_:)), name: NSNotification.Name.UIApplicationDidBecomeActive, object: nil)
}

@objc func applicationDidBecomeActive(_ notification:Notification)
{
    self.view.layoutIfNeeded()
}

override func viewWillDisappear(_ animated: Bool) {
    NotificationCenter.default.removeObserver(self, name: NSNotification.Name.UIApplicationDidBecomeActive, object: nil)
}

Answer 2

原因：

在BG中呆了很长时间后，它将调用draw（）函数重绘View。就像视图的高度为0一样，它什么也不会画。

解决方案：

使用CAShapeLayer更新路径。

@IBInspectable var mainColor: UIColor = UIColor.blue

private var bottomLayer : CAShapeLayer = CAShapeLayer()

override func awakeFromNib() {
    super.awakeFromNib()

    bottomLayer = CAShapeLayer()
    bottomLayer.strokeColor = mainColor.cgColor
    bottomLayer.fillColor = mainColor.cgColor
    bottomLayer.lineWidth = 1
    bottomLayer.backgroundColor = UIColor.clear.cgColor
    bottomLayer.path = self.getPath().cgPath

    self.layer.addSublayer(bottomLayer)
}

override func layoutSubviews() {
    super.layoutSubviews()

    self.bottomLayer.frame = self.bounds
    self.bottomLayer.path = self.getPath().cgPath
}

应用转到背景一段时间后，CoreGraphic的视图绘制消失了

2 个答案: