如何使用touchesMoved函数正确更新曲线？

Question

我想制作一条曲线，当用户移动他们的手指时，曲线改变了它的弧度，但是我所做的代码看起来有些不对劲，当我移动手指时有很多曲线:(这是我的代码，然后跟着可怕的build的截图。实际上我也想知道如何用UIPanGestureRecognizer实现这个功能。

import SpriteKit
import AVFoundation
import UIKit

class Home: SKScene {

    var happiness:CGFloat {
        return currentPoint.y
    }

    var currentPoint = CGPoint(x: 0, y: 1024)

    override func didMoveToView(view: SKView) {
        backgroundColor = UIColor.blueColor()
    }

    func drawhappiness() {
        let pathNew2 = CGPathCreateMutable()
        let startx:CGFloat = 268
        let starty:CGFloat = 1024
        let cp1x:CGFloat = 568
        let cp1y:CGFloat = happiness
        let cp2x:CGFloat = 968
        let cp2y:CGFloat = happiness
        let endx:CGFloat = 1292
        let endy:CGFloat = 1024
        CGPathMoveToPoint(pathNew2, nil, startx, starty)
        CGPathAddCurveToPoint(pathNew2, nil, cp1x, cp1y, cp2x, cp2y, endx, endy)
        let shapeNew2 = SKShapeNode()
        shapeNew2.path = pathNew2
        shapeNew2.strokeColor = UIColor.greenColor()
        shapeNew2.lineWidth = 10
        addChild(shapeNew2)
    }

    override func touchesMoved(touches: Set<NSObject>, withEvent event: UIEvent) {
        for touch:AnyObject in touches {
            currentPoint = touch.locationInNode(self)
        }
    }

    override func update(currentTime: NSTimeInterval) {
        drawhappiness()
    }
}

Answer 1

每次移动手指时，都会向场景添加新的形状节点。 要解决此问题，请在Home创建具有全局范围的单个形状，在didMoveToView配置形状（即设置线宽，颜色），并在drawhappiness更新形状的path属性。

例如，

class Home: SKScene {

    let shapeNew2 = SKShapeNode()
    var currentPoint = CGPoint(x: 0, y: 1024)

    var happiness:CGFloat {
        return currentPoint.y
    }

    override func didMoveToView(view: SKView) {
        backgroundColor = UIColor.blueColor()
        shapeNew2.strokeColor = UIColor.greenColor()
        shapeNew2.lineWidth = 10
        addChild(shapeNew2)
    }

    func drawhappiness() {
        let pathNew2 = CGPathCreateMutable()
        let startx:CGFloat = 268
        let starty:CGFloat = 1024
        let cp1x:CGFloat = 568
        let cp1y:CGFloat = happiness
        let cp2x:CGFloat = 968
        let cp2y:CGFloat = happiness
        let endx:CGFloat = 1292
        let endy:CGFloat = 1024
        CGPathMoveToPoint(pathNew2, nil, startx, starty)
        CGPathAddCurveToPoint(pathNew2, nil, cp1x, cp1y, cp2x, cp2y, endx, endy)
        shapeNew2.path = pathNew2
    }

    override func touchesMoved(touches: Set<NSObject>, withEvent event: UIEvent) {
        for touch:AnyObject in touches {
            currentPoint = touch.locationInNode(self)
        }
    }

    override func update(currentTime: NSTimeInterval) {
        drawhappiness()
    }
}