ios - SpriteKit 和 Swift : Creating nodes via didBeginContact messes up the positioning

Question

我不知道这是 Xcode 中的一个奇怪错误还是 SpriteKit 的坐标系统有什么我不明白的地方。

前提是节点的位置总是相对于它的父节点。但是，每当我从 SKPhysicsContactDelegate 的“didBeginContact”调用创建和定位具有物理体的节点的 block 时，该节点始终相对于场景(而不是其父级)定位。请注意，在除“didBeginContact”以外的任何地方触发时，调用同一个 block 都会按预期工作。另一件事是，如果我移除所述节点的物理主体，即使从“didBeginContact”调用时，该 block 现在也会按预期工作。

我已经被这个问题困扰了两天，如果不提供有关我的实际代码的其他详细信息，那就太麻烦了。所以我做了一个非常简单的项目来演示这个异常。只需使用 Spritekit 模板在 Xcode 6 中创建一个新项目，并将 GameViewController.swift 和 GameSwift.swift 替换为下面发布的代码。只需在 iPad Air 中运行，其他一切都应该是不言自明的。

最后的笔记:

1. 当您按下第一个按钮并与第二个按钮建立联系时按钮，查看屏幕的左下角。你会看见这些盒子被“错误地”放置在那里。
2. 尝试删除“AddBox”中盒子的物理实体。它现在将按预期工作。
3. 如果您认为这是一个错误，或者坐标系或物理世界中有我不理解的地方，请告诉我

GameViewController.swift:

import SpriteKit

class GameViewController: UIViewController {
    override func viewDidLoad() {
        super.viewDidLoad()
        let scene = GameScene()
        scene.size = view.frame.size
        let skView = self.view as SKView
        scene.scaleMode = .AspectFill
        skView.presentScene(scene)
    }
}

GameScene.swift:

import SpriteKit

let kButtonSize = CGSize(width: 500, height: 100)
let kContainerSize = CGSize(width: 500, height: 300)
let kBoxSize = CGSize(width: 25, height: 25)

class GameScene: SKScene, SKPhysicsContactDelegate {

    override func didMoveToView(view: SKView) {
        physicsWorld.contactDelegate = self
        addFirstButton()
        addSecondButton()
        addContainer()
    }

    func addFirstButton() {
        let button = SKSpriteNode(color: SKColor.blueColor(), size: kButtonSize)
        let label = SKLabelNode(text: "Call 'addBox' from didBeginContact")
        button.name = "firstButton"
        label.name = "firstLabel"
        button.position = CGPointMake(CGRectGetMidX(frame), CGRectGetMidY(frame))
        button.physicsBody = SKPhysicsBody(rectangleOfSize: button.size)
        button.physicsBody.allowsRotation = false
        button.physicsBody.affectedByGravity = false
        button.physicsBody.categoryBitMask = 0x1
        button.physicsBody.contactTestBitMask = 0x1
        button.addChild(label)
        addChild(button)
    }

    func addSecondButton() {
        let button = SKSpriteNode(color: SKColor.blueColor(), size: kButtonSize)
        let label = SKLabelNode(text: "Call 'addBox' from touchesBegan")
        button.name = "secondButton"
        label.name = "secondLabel"
        button.position = CGPointMake(CGRectGetMidX(frame), CGRectGetMidY(frame)-200)
        button.physicsBody = SKPhysicsBody(rectangleOfSize: button.size)
        button.physicsBody.dynamic = false
        button.physicsBody.categoryBitMask = 0x1
        button.physicsBody.contactTestBitMask = 0x1
        button.addChild(label)
        addChild(button)
    }

    func addContainer() {
        let container = SKSpriteNode(color: SKColor.greenColor(), size:kContainerSize)
        let label = SKLabelNode(text: "Created node should fall here")
        label.fontColor = SKColor.blackColor()
        container.name = "container"
        container.physicsBody = SKPhysicsBody(edgeLoopFromRect: container.frame)
        container.position = CGPointMake(CGRectGetMidX(frame), CGRectGetMidY(frame)+300)
        container.addChild(label)
        addChild(container)
    }

    func addBox() {
        let container = childNodeWithName("container")
        let box = SKSpriteNode(color: SKColor.blueColor(), size: kBoxSize)
        box.physicsBody = SKPhysicsBody(rectangleOfSize: box.size)
        box.position = CGPointMake(0, 100)
        container.addChild(box)
    }

    override func touchesBegan(touches: NSSet, withEvent event: UIEvent) {
        let touch = touches.anyObject() as UITouch
        let point = touch.locationInNode(self)
        let node = nodeAtPoint(point)
        if node.name == nil {return}

        switch node.name! {
        case "firstButton", "firstLabel":
            let button = childNodeWithName("firstButton") as SKSpriteNode
            button.physicsBody.applyImpulse(CGVectorMake(0, -500))
        case "secondButton", "secondLabel":
            addBox()
        default:
            break
        }
    }

    func didBeginContact(contact: SKPhysicsContact!) {
        addBox()
    }
}

Answer 1

我已经通过 Apple Bug Report 提交了关于此问题的票证。我希望这可以帮助遇到相同问题的任何人。这是他们的回应:

Apple Developer Relations24-Sep-2014 04:40 AM

Engineering has determined that this is an issue for you to resolve based on the following:

You can't modify a tree which it is being simulated, and this is clearly stated in Programming Guide.