ios - 怎么移线？

Question

如何在垂直方向上移动水平线？ 我可以画一条水平直线，我需要使用长按来移动它。 我该怎么做？

override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?)
{
    if let touch = touches.first 
    {
        let currentPoint = touch.location(in: self.view)
        DrawLine(FromPoint: currentPoint, toPoint: currentPoint)
    }
}
func DrawLine(FromPoint: CGPoint, toPoint: CGPoint)
{
    UIGraphicsBeginImageContext(self.view.frame.size)
    imageView.image?.draw(in: CGRect(x: 0, y: 0, width: self.view.frame.width, height: self.view.frame.height))
    let context = UIGraphicsGetCurrentContext()
    let lineWidth : CGFloat = 5
    context?.move(to: CGPoint(x: FromPoint.x, y: FromPoint.y))
    context?.addLine(to: CGPoint(x: FromPoint.x + 200, y: FromPoint.y))
    context?.setBlendMode(CGBlendMode.normal)
    context?.setLineCap(CGLineCap.round)
    context?.setLineWidth(lineWidth)
    context?.setStrokeColor(UIColor(red: 0, green: 0, blue: 0, alpha: 1.0).cgColor)
    context?.strokePath()
    imageView.image = UIGraphicsGetImageFromCurrentImageContext()
    UIGraphicsEndImageContext()
}

Answer 1

您可以使用 UIView 绘制水平线，并可以通过提供所需选项使用 UIView.animate 方法在垂直方向移动它。

在您的 ViewController 中定义以下变量:

var scanlineRect = CGRect.zero
var scanlineStartY: CGFloat = 0
var scanlineStopY: CGFloat = 0
var topBottomMargin: CGFloat = 30
var scanLine: UIView = UIView()

在 viewDidLoad 方法中调用 drawLine 方法，并在触摸事件中调用 moveVertically 方法:

func drawLine() {
        self.addSubview(scanLine)
        scanLine.backgroundColor = UIColor(red: 0.4, green: 0.8, blue: 0.4, alpha: 1.0) // green color
        scanlineRect = CGRect(x: 0, y: 0, width: self.frame.width, height: 2)
        scanlineStartY = topBottomMargin
        scanlineStopY = self.frame.size.height - topBottomMargin
    }

func moveVertically() {
        scanLine.frame  = scanlineRect
        scanLine.center = CGPoint(x: scanLine.center.x, y: scanlineStartY)
        scanLine.isHidden = false
        weak var weakSelf = scanLine
        UIView.animate(withDuration: 1.0, delay: 0.0, options: [.repeat, .autoreverse, .beginFromCurrentState], animations: {() -> Void in
            weakSelf!.center = CGPoint(x: weakSelf!.center.x, y: scanlineStopY)
            }, completion: nil)
    }