swift - 如何在一定范围内用操纵杆 move Sprite ？

Question

我想让玩家可以用操纵杆 move 但不能离开圆圈。我做了操纵杆，但我不知道怎么做其他的东西。下图中有一个示例，还有我的代码。希望有人能帮助我，谢谢。

class GameScene: SKScene {

    var circuloPrincipal = SKSpriteNode(imageNamed: "circulo")
    var circuloFondo = SKSpriteNode(imageNamed: "circuloFondo")
    let base = SKSpriteNode(imageNamed: "circuloFondo")
    let ball = SKSpriteNode(imageNamed: "circulo")
    var stickActive:Bool = false



    override func didMoveToView(view: SKView) {
        /* Setup your scene here */

        base.size = CGSize(width: 100, height: 100)
        base.alpha = 0.3
        base.zPosition = 2.0
        base.position = CGPoint(x: frame.width / 2, y: frame.height / 2 - 310)
        self.addChild(base)

        ball.size = CGSize(width: 50, height: 50)
        ball.color = circuloPrincipal.color
        //ball.alpha = 0
        ball.zPosition = 3.0
        ball.position = base.position
        self.addChild(ball)

        circuloPrincipal.size = CGSize(width: 35, height: 35)
        circuloPrincipal.position = CGPoint(x: frame.width / 2, y: frame.height / 2)
        self.addChild(circuloPrincipal)
        circuloPrincipal.color =  UIColor(red: 0.75, green: 0.75, blue: 0.75, alpha: 1.0)
        circuloPrincipal.colorBlendFactor = 1.0
        circuloPrincipal.zPosition = 3.0
    }

    override func touchesBegan(touches: Set<UITouch>, withEvent event:     UIEvent?) {


        for touch in touches {
            let location = touch.locationInNode(self)

            if (CGRectContainsPoint(ball.frame, location)) {

                stickActive = true
            }else {

                stickActive = false

            }

        }
    }

    override func touchesMoved(touches: Set<UITouch>, withEvent event: UIEvent?) {
        for touch in touches {
            let location = touch.locationInNode(self)

            if (stickActive == true) {


            let v = CGVector(dx: location.x - base.position.x, dy: location.y - base.position.y)
            let angle = atan2(v.dy, v.dx)
            let deg = angle * CGFloat(180 / M_PI)
            print(deg + 180)

            let lenght:CGFloat = base.frame.size.height / 2 - 20
            let xDist: CGFloat = sin(angle - 1.57079633) * lenght
            let yDist: CGFloat = cos(angle - 1.57079633) * lenght

            ball.position = CGPointMake(base.position.x - xDist, base.position.y + yDist)

            if (CGRectContainsPoint(base.frame, location)) {

                ball.position = location
            }else {

                ball.position = CGPointMake(base.position.x - xDist, base.position.y + yDist)

            }


            } // termina stickActive

        }

    }

    override func touchesEnded(touches: Set<UITouch>, withEvent event: UIEvent?) {
        if (stickActive == true) {

            let move: SKAction = SKAction.moveTo(base.position, duration: 0.2)
            move.timingMode = .EaseOut

            ball.runAction(move)

        }
    }

Answer 1

查看 SKConstraint - 你可以设置一个约束，一个节点不能 move 超过与另一个节点的指定距离。您可以将此“其他”节点设置为您的玩家所限制区域的中心。 Sprite-Kit 会自动将您的节点移回原处。由于这是在节点 move 后重新绘制之前以 60fps 的速度进入游戏循环，因此您不会得到任何奇怪的“跳跃”效果。

https://developer.apple.com/reference/spritekit/skconstraint

与其他一些 SK 文档相比，该文档有点缺乏。这是一个使绿色矩形“跟随”指定距离内的黄色三角形的示例:

let distanceRange = SKRange(lowerLimit: 200, upperLimit: 400)
let distanceConstraint = SKConstraint.distance(distanceRange, toNode: yellowTriangle)  
greenRect.constraints = [distanceConstraint]

SKNode (greenRect) 的 constraints 属性是一个数组，因此如果您还想要一个方向约束(例如，让 greenRect 面向黄色三角形)，您可以编写如下代码:

let orientRange = SKRange(lowerLimit: 0.0, upperLimit: 0.0)
let orientConstraint = SKConstraint.orientToNode(yellowTriangle, offset: orientRange)
greenRect.constraints = [orientatConstraint, distanceConstraint]

对于您的特定示例，您可能希望将约束设置为:

let distanceRange = SKRange(lowerLimit: 0, upperLimit: limitcircle.size/2)
 let distanceConstraint = SKConstraint.distance(distanceRange, toPoint: limitCircle.position)
player.constraints = [distanceConstraint]

这假设玩家无法 move 的圆圈是一个名为 limitcircle 的 SKNode，它的 anchor 设置为 (0.5, 0.5)，即它的中心。上面的代码会将玩家限制在距离圆心点的圆宽度(即半径)的 0 到 1/2 之间。