我如何使圆形视图与桨发生碰撞

Question

每当圆形视图与情节提要上的桨碰撞时，它实际上与视图的矩形框架发生碰撞。我该如何解决这个问题。我也试过UIBezierPath、CAShapeLayer，但似乎没有用。

红色箭头是碰撞点，因为它似乎没有与球碰撞，而是与视图的框架发生碰撞。一次，框架被它反弹回来的桨触摸等等。

Answer 1

如果您使用UIDynamicAnimator，您可以为将发生碰撞的项目定义collisionBoundsType 和collisionBoundingPath，例如：

@IBDesignable public class BallView : UIView {

    @IBInspectable public var fillColor: UIColor = UIColor.blackColor() {
        didSet { setNeedsLayout() }
    }

    override public var collisionBoundsType: UIDynamicItemCollisionBoundsType {
        return .Path
    }

    override public var collisionBoundingPath: UIBezierPath {
        let radius = min(bounds.size.width, bounds.size.height) / 2.0

        return UIBezierPath(arcCenter: CGPointZero, radius: radius, startAngle: 0, endAngle: CGFloat(M_PI * 2.0), clockwise: true)
    }

    private var shapeLayer: CAShapeLayer!

    public override func layoutSubviews() {
        if shapeLayer == nil {
            shapeLayer = CAShapeLayer()
            shapeLayer.strokeColor = UIColor.clearColor().CGColor
            layer.addSublayer(shapeLayer)
        }

        let radius = min(bounds.size.width, bounds.size.height) / 2.0

        shapeLayer.fillColor = fillColor.CGColor
        shapeLayer.path = UIBezierPath(arcCenter: CGPoint(x: bounds.size.width / 2.0, y: bounds.size.height / 2.0), radius: radius, startAngle: 0, endAngle: CGFloat(M_PI * 2.0), clockwise: true).CGPath
    }
}

@IBDesignable public class PaddleView : UIView {

    @IBInspectable public var cornerRadius: CGFloat = 5 {
        didSet { setNeedsLayout() }
    }

    @IBInspectable public var fillColor: UIColor = UIColor.blackColor() {
        didSet { setNeedsLayout() }
    }

    override public var collisionBoundsType: UIDynamicItemCollisionBoundsType {
        return .Path
    }

    override public var collisionBoundingPath: UIBezierPath {
        return UIBezierPath(roundedRect: CGRect(x: -bounds.size.width / 2.0, y: -bounds.size.height / 2.0, width: bounds.width, height: bounds.height), cornerRadius: cornerRadius)
    }

    private var shapeLayer: CAShapeLayer!

    public override func layoutSubviews() {
        if shapeLayer == nil {
            shapeLayer = CAShapeLayer()
            shapeLayer.strokeColor = UIColor.clearColor().CGColor
            layer.addSublayer(shapeLayer)
        }

        shapeLayer.fillColor = fillColor.CGColor
        shapeLayer.path = UIBezierPath(roundedRect: CGRect(x: 0, y: 0, width: bounds.width, height: bounds.height), cornerRadius: cornerRadius).CGPath
    }
}

如果您这样做，然后将这些项目添加到您的UICollisionBehavior，它将尊重您为项目定义的冲突边界。例如：

---

上图说明了一个扫视，就像您的原始图像一样。如果你想让它即使碰到桨的边缘也能弹起来，你可以为UICollisionBehavior指定collisionDelegate并给它一个新的方向：

let collision = UICollisionBehavior(items: [paddleView, ballView])
collision.translatesReferenceBoundsIntoBoundary = true
collision.collisionDelegate = self
self.animator.addBehavior(collision)

并符合UICollisionBehaviorDelegate再执行collisionBehavior(beganContactForItem:withItem:atPoint:)：

func collisionBehavior(behavior: UICollisionBehavior, beganContactForItem item1: UIDynamicItem, withItem item2: UIDynamicItem, atPoint p: CGPoint) {
    let postCollisionDirection = UIDynamicItemBehavior(items: [ballView])
    postCollisionDirection.addLinearVelocity(CGPoint(x: ballView.center.x - paddleView.center.x, y: -200), forItem: ballView)
    animator.addBehavior(postCollisionDirection)
}

这会产生如下内容：

显然，您必须花很多时间才能获得所需的效果，但它说明了检测碰撞并相应地为球添加线速度的基本思想。

Answer 2

比公认的答案更简单的答案是将边界设置为椭圆而不是定义的路径：

 override public var collisionBoundsType: UIDynamicItemCollisionBoundsType {
        return .Elliptical
 }