无法将 PhysicsBody 和属性分配给 SKSpriteNode？答案

【问题标题】：Cannot assign PhysicsBody and property to an SKSpriteNode?无法将 PhysicsBody 和属性分配给 SKSpriteNode？
【发布时间】：2020-05-07 16:42:05
【问题描述】：

我正在构建一个函数，其中一个随机变量将在一个数组中选择 4 个 SKSpritenode 中的 1 个并将自己分配给它。然而，该随机线虽然按预期出现在屏幕上，但不包含任何物理体属性，因此它不会与其他节点发生碰撞。以下是我的代码：

func line() {

        redLine = SKSpriteNode(imageNamed: "redline")
        blueLine = SKSpriteNode(imageNamed: "blueline")
        yellowLine = SKSpriteNode(imageNamed: "yellowline")
        greenLine = SKSpriteNode(imageNamed: "greenline")

        let lineArray = [redLine,blueLine,yellowLine,greenLine]
        // Add physics
        lineArray[0].physicsBody?.categoryBitMask = gamePhysics.RedLine
        lineArray[1].physicsBody?.categoryBitMask = gamePhysics.BlueLine
        lineArray[2].physicsBody?.categoryBitMask = gamePhysics.YellowLine
        lineArray[3].physicsBody?.categoryBitMask = gamePhysics.GreenLine

        for i in 0...3 {
            lineArray[i].physicsBody = SKPhysicsBody(circleOfRadius: 10)
            lineArray[i].physicsBody?.collisionBitMask = gamePhysics.RedBall | gamePhysics.BlueBall | gamePhysics.YellowBall | gamePhysics.GreenBall
            lineArray[i].physicsBody?.contactTestBitMask = gamePhysics.RedBall | gamePhysics.BlueBall | gamePhysics.YellowBall | gamePhysics.GreenBall
            lineArray[i].physicsBody?.affectedByGravity = false
            lineArray[i].physicsBody?.isDynamic = true
        }
        let randomLine:SKSpriteNode! = lineArray.randomElement()
        ...

        self.addChild(randomLine)
        ...

        randomLine.run(SKAction.sequence([moveLine,delay,removeLine]))
    }

所以基本上当随机线与其他节点碰撞时，什么都不会发生。

这是我的 didBegin（联系人）函数：

func didBegin(_ contact: SKPhysicsContact) {
        let firstBody = contact.bodyA
        let secondBody = contact.bodyB

        if firstBody.categoryBitMask == gamePhysics.RedBall && secondBody.categoryBitMask == gamePhysics.RedLine || firstBody.categoryBitMask == gamePhysics.BlueBall && secondBody.categoryBitMask == gamePhysics.BlueLine || firstBody.categoryBitMask == gamePhysics.YellowBall && secondBody.categoryBitMask == gamePhysics.YellowLine || firstBody.categoryBitMask == gamePhysics.GreenBall && secondBody.categoryBitMask == gamePhysics.GreenLine {

            currentScore += 1
            secondBody.node?.removeFromParent()
            print("hit point")

        } else if firstBody.categoryBitMask == gamePhysics.RedLine && secondBody.categoryBitMask == gamePhysics.RedBall || firstBody.categoryBitMask == gamePhysics.BlueLine && secondBody.categoryBitMask == gamePhysics.BlueBall || firstBody.categoryBitMask == gamePhysics.YellowLine && secondBody.categoryBitMask == gamePhysics.YellowBall || firstBody.categoryBitMask == gamePhysics.GreenLine && secondBody.categoryBitMask == gamePhysics.GreenBall {

            currentScore += 1
            firstBody.node?.removeFromParent()
            print("hit point")

        }
    }

任何帮助将不胜感激！编辑：这是球 func()。也许不知何故 SKNode 包含多个类别位掩码，因此不起作用？

func Ball() {

        ballNode = SKNode()
        redBall = SKSpriteNode(imageNamed: "redball")
        blueBall = SKSpriteNode(imageNamed: "blueball")
        yellowBall = SKSpriteNode(imageNamed: "yellowball")
        greenBall = SKSpriteNode(imageNamed: "greenball")

        let ballArray = [redBall,blueBall,yellowBall,greenBall]
        ...

        // Add physics
        ballArray[0].physicsBody?.categoryBitMask = gamePhysics.RedBall
        ballArray[1].physicsBody?.categoryBitMask = gamePhysics.BlueBall
        ballArray[2].physicsBody?.categoryBitMask = gamePhysics.YellowBall
        ballArray[3].physicsBody?.categoryBitMask = gamePhysics.GreenBall

        for i in 0...3 {
            ballArray[i].physicsBody = SKPhysicsBody(circleOfRadius: 20)
            ballArray[i].physicsBody?.collisionBitMask = gamePhysics.RedLine | gamePhysics.BlueLine | gamePhysics.YellowLine | gamePhysics.GreenLine
            ballArray[i].physicsBody?.contactTestBitMask = gamePhysics.RedLine | gamePhysics.BlueLine | gamePhysics.YellowLine | gamePhysics.GreenLine
            ballArray[i].physicsBody?.affectedByGravity = false
            ballArray[i].physicsBody?.isDynamic = false
        }

        ballNode.addChild(redBall)
        ballNode.addChild(greenBall)
        ballNode.addChild(yellowBall)
        ballNode.addChild(blueBall)

        self.addChild(ballNode)
    }

更新 2：这是我存储类别位掩码的结构：

struct gamePhysics {

    static let RedBall : UInt32 = 0x1 << 1
    static let BlueBall : UInt32 = 0x1 << 2
    static let GreenBall : UInt32 = 0x1 << 3
    static let YellowBall : UInt32 = 0x1 << 4
    static let RedLine : UInt32 = 0x1 << 5
    static let BlueLine : UInt32 = 0x1 << 6
    static let GreenLine : UInt32 = 0x1 << 7
    static let YellowLine : UInt32 = 0x1 << 8
}

【问题讨论】：

标签： swift xcode skspritenode skphysicsbody sknode

【解决方案1】：

您还记得在场景中设置联系人代理吗？将这行代码放入didMove(to:):

self.physicsWorld.contactDelegate = self

如果这不能解决问题，我会在&& 和|| 语句之间使用括号使didBegin 中的if 条件更加明确。

查看其余代码，我看不出还有什么问题，您所做的应该可以工作。您放置在 if 语句中的 print("hit point") 是否已到达？

【讨论】：

嗨，是的，我确实包含了 self.physicsWorld.contactDelegate = self 但它不起作用。而且 print("hit point") 根本没有运行，所以我认为有些东西阻止了代码进入那个 if 语句......最初我认为是因为我将“随机线”放在了 addChild 函数中。但是，当我尝试对单行使用 addChild 方法时，它仍然没有解决任何问题……也许该行已经以某种方式分配了物理体？ categorybit 掩码不起作用？
categoryBitMasks 的值是多少？
我将它存储在一个结构中，就像我对我的问题所做的编辑一样。这是一个 UInt32 值。

【解决方案2】：

天哪，我找到了我的问题的答案。 categorybitmask 的值返回“nil”的原因是因为我实际上在指定其物理体之前将节点分配给 categorybitmask。将行向下移动几行，一切都解决了！

【讨论】：