为什么有多个碰撞调用 Sprite Kit Swift

Question

我正在构建一个带有碰撞的 iOS 快速游戏。英雄正被屏幕右侧的小星星轰炸。每次星星击中英雄时，都会迭代得分并移除星星。但是，分数会增加一分以上。

节点设置：

var star = SKSpriteNode(imageNamed: "star")
star.size = CGSizeMake(30, 30)
star.zPosition = 10
var starPhysicsRect = CGRectMake(star.position.x - star.frame.size.width / 2, star.position.y - star.frame.size.width / 2, star.frame.size.width, star.frame.size.height)
star.physicsBody = SKPhysicsBody(edgeLoopFromRect: starPhysicsRect)
star.physicsBody?.restitution = 0
star.name = "star"
star.physicsBody?.mass = 0
return star

didBeginContact 函数：

func didBeginContact(contact: SKPhysicsContact) {
    //collision variables
    var firstBodyNode = contact.bodyA.node as! SKSpriteNode
    var secondBodyNode = contact.bodyB.node as! SKSpriteNode
    var firstNodeName = firstBodyNode.name
    var secondNodeName = secondBodyNode.name

    //other variables
    var scoreLabel: SKLabelNode = constantsInstance.scoreLabel(position: CGPointMake(self.frame.size.width * 0.86, self.frame.size.height * 0.928))


    //check if hero hit star
    if firstNodeName == "hero" && secondNodeName == "star" {
        println("star hit")
        secondBodyNode.removeFromParent()

        //iterate score
        childNodeWithName("scoreLabel")?.removeFromParent()
        scoreLabel.text = "\(counterForScore)"
        counterForScore++
        self.addChild(scoreLabel)
    }
}

我也多次将“star hit”打印到控制台。如果我在第一次调用函数时去掉星号，为什么会多次调用 didBeginContact 函数？

我运行了较小规模的模拟，发现如果没有移除命令，星星会相当深入地进入英雄（因为 SKAction）。会不会是在星星进入英雄的过程中，在被移除之前多次调用了didBeginContact函数？

非常感谢所有帮助。

Answer 1

您可以在继续之前检查SKSpriteNode 的父级是否为零。

func didBeginContact(contact: SKPhysicsContact) {
    var firstBodyNode : SKSpriteNode!
    var secondBodyNode : SKSpriteNode!

    //  Assuming that the contact test bit mask of star is greater than hero. If it's not you should reverse the condition.

    if contact.bodyA.contactTestBitMask < contact.bodyB.contactTestBitMask {
        firstBodyNode = contact.bodyA.node as! SKSpriteNode
        secondBodyNode = contact.bodyB.node as! SKSpriteNode
    } else {
        firstBodyNode = contact.bodyB.node as! SKSpriteNode
        secondBodyNode = contact.bodyA.node as! SKSpriteNode
    }

    var firstNodeName = firstBodyNode.name
    var secondNodeName = secondBodyNode.name

    if firstNodeName == "hero" && secondNodeName == "star" {
        if secondBodyNode.parent != nil {
           // Your code.
        }
    }
}

Answer 2

可能是由于physicsBody：

var star = SKSpriteNode(imageNamed: "star")
star.size = CGSizeMake(30, 30)
star.zPosition = 10
var starPhysicsRect = CGRectMake(star.position.x - star.frame.size.width / 2, star.position.y - star.frame.size.width / 2, star.frame.size.width, star.frame.size.height)
star.physicsBody = SKPhysicsBody(edgeLoopFromRect: starPhysicsRect)

看看创建starPhysicsRect的逻辑：

(star.position.x - star.frame.size.width / 2, star.position.y - star.frame.size.width / 2, star.frame.size.width, star.frame.size.height)

据我所知，这转化为以下值： (-15, -15, 30, 30) 那些负位置坐标看起来很奇怪。你确定你不只是想要：SKPhysicsBody(rectangleOfSize: star.size) 吗？