SKShapeNode定位

Question

我在SpriteKit周围打探，发现了一些奇怪的地方，我只是在iPhone上添加应该是全屏的矩形SKShapeNode。

override func didMoveToView(view: SKView) {
    let _box            = SKShapeNode(rectOfSize: self.frame.size)
    _box.strokeColor    = SKColor.blueColor()
    _box.fillColor      = SKColor.blueColor()
    _box.position       = CGPointMake(200, 200)
    _box.name           = "box"
    self.addChild(_box)

    let _player         = SKShapeNode(circleOfRadius: 50)
    _player.position    = CGPoint(x:CGRectGetMidX(self.frame), y:CGRectGetMidY(self.frame))
    _player.fillColor   = SKColor.redColor()
    _player.strokeColor = SKColor.redColor()
    _player.name        = "player"
    _player.physicsBody = SKPhysicsBody(circleOfRadius: 50)
    _player.physicsBody?.dynamic = true
    _player.physicsBody?.allowsRotation = false
    self.addChild(_player)

    let _ground         = SKShapeNode(rectOfSize: CGSizeMake(self.frame.width, 20))
    _ground.name        = "ground"
    _ground.position    = CGPointMake(0, 0)
    _ground.fillColor   = SKColor.greenColor()
    _ground.strokeColor = SKColor.greenColor()
    _ground.physicsBody = SKPhysicsBody(rectangleOfSize: CGSizeMake(self.frame.width, 20))
    _ground.physicsBody?.dynamic = false
    self.addChild(_ground)
}

我的视图是这样初始化的:覆盖func viewDidLoad() { super.viewDidLoad() }

override func viewWillLayoutSubviews() {
    super.viewWillLayoutSubviews()
    if let scene = GameScene.unarchiveFromFile("GameScene") as? GameScene {
        // Configure the view.
        let skView = self.view as SKView
        skView.showsFPS = true
        skView.showsNodeCount = true

        /* Sprite Kit applies additional optimizations to improve rendering performance */
        skView.ignoresSiblingOrder = true

        /* Set the scale mode to scale to fit the window */
        scene.scaleMode = .AspectFill

        skView.presentScene(scene)
    }

}

生成的场景如下：屏幕截图

所有节点都移到左侧底部。基本上，矩形形状的左下角超出了界限(我已经检查过，通过将蓝色形状定位为(200,200)而不是(0，0)，左瓶边缘仍然超出了屏幕框架。

场景的锚点被设置为(0，0)，所以它对我来说基本上是一样的，它为形状的中心点设置位置。

什么是定义节点左下角位置的最佳方法，而不是中点？

Answer 1

如果使用bezier路径或CGPath创建形状，则可以指定其“锚点”的位置，其中路径的原点指定路径的下/左角。例如,

    UIBezierPath* bezierPath = [UIBezierPath bezierPathWithRect: CGRectMake(0, 0, 50, 50)];
    SKShapeNode *shape = [SKShapeNode node];
    shape.path = bezierPath.CGPath;
    shape.fillColor = [SKColor blueColor];

此外，如果您的部署目标是iOS 8，则可以使用

    SKShapeNode *shape = [SKShapeNode shapeNodeWithRect:CGRectMake(0, 0, 50, 50)];
    shape.fillColor = [SKColor blueColor];

Answer 2

_box.position       = CGPointMake(self.size.width*.5, self.size.height*.5)

这将定位您的精灵的中心在屏幕的中心。