未调用 UICollisionBehaviorDelegate 方法

Question

我开发了一个应用程序并使用 UIKitDynamics 实现了碰撞检测。

碰撞检测正在运行。但不知何故 UICollisionBehaviorDelegate 方法没有被调用。未显示任何警告或错误。

我创建了一个示例项目来演示该问题：

  import UIKit

  class ViewController: UIViewController {
    private var dynamicAnimator: UIDynamicAnimator?

    override func viewDidLoad() {
      super.viewDidLoad()
      // Do any additional setup after loading the view, typically from a nib.
    }

    override func viewDidAppear(_ animated: Bool) {
      super.viewDidAppear(animated)

      self.initPhysics()
    }

    fileprivate var initalized = false
    fileprivate func initPhysics() {
      if initalized {
        return
      }
      initalized = true

      let physicsView = UIView(frame: view.bounds.insetBy(dx: 40, dy: 40))
      physicsView.backgroundColor = UIColor.black

      self.dynamicAnimator = UIDynamicAnimator(referenceView: physicsView)

      physicsView.isUserInteractionEnabled = false
      view.addSubview(physicsView)

      //Create ball
      let frame = CGRect(x: 0, y: 0, width: 40, height: 40)

      let rect = UIView(frame: frame)
      rect.backgroundColor = UIColor.red
      physicsView.addSubview(rect)

      let behavior = UIDynamicItemBehavior(items: [rect])
      behavior.elasticity = 1.0
      behavior.resistance = 0.0
      behavior.friction = 0.0
      behavior.allowsRotation = false
      self.dynamicAnimator?.addBehavior(behavior)

      //collision behavior setup
      let collisionBehavior = UICollisionBehavior(items: [rect])
      collisionBehavior.collisionDelegate = self
      collisionBehavior.setTranslatesReferenceBoundsIntoBoundary(with: .zero)
      collisionBehavior.collisionMode = .everything
      self.dynamicAnimator?.addBehavior(collisionBehavior)

      //Push ball
      let pushBehavior = UIPushBehavior(items: [rect], mode: UIPushBehaviorMode.instantaneous)
      pushBehavior.active = true
      pushBehavior.pushDirection = CGVector(dx: 0.5, dy: 0.5)
      self.dynamicAnimator?.addBehavior(pushBehavior)
    }
  }

  extension ViewController: UICollisionBehaviorDelegate {
    // DELEGATE METHODS NOT CALLED
    func collisionBehavior(_ behavior: UICollisionBehavior,
                           beganContactFor item: UIDynamicItem,
                           withBoundaryIdentifier identifier: NSCopying?,
                           at p: CGPoint) {
      print("began contact boundary")
    }

    func collisionBehavior(_ behavior: UICollisionBehavior,
                           endedContactFor item: UIDynamicItem,
                           withBoundaryIdentifier identifier: NSCopying?) {
      print("contact boundary ended")
    }

    func collisionBehavior(_ behavior: UICollisionBehavior,
                           endedContactFor item1: UIDynamicItem,
                           with item2: UIDynamicItem) {

      print("contact item ended")
    }

    func collisionBehavior(_ behavior: UICollisionBehavior,
                           beganContactFor item1: UIDynamicItem,
                           with item2: UIDynamicItem,
                           at p: CGPoint) {
      print("began contact item")
    }
  }

基础 SDK：iOS11.2，Xcode9.2 版 (9C40b)

感谢您的帮助！

Answer 1

这不是它的工作方式（可悲）..你的碰撞行为中只有一个项目，你要求它检测与什么的碰撞？？？如果您添加了第二个项目，您将看到代理被调用..

真正的问题是为什么？好吧，碰撞检测一个项目的框架是否与另一个项目的框架相交。如果它做了你所要求的（rect 是 physicsView 的 child），那么它总是会发生碰撞（这不是你想要的）..

因为你的 physicsView 不是碰撞行为的一部分，你什么也得不到。你告诉它把项目限制在它的范围内（setTranslatesReferenceBoundsIntoBoundary 对添加到行为的项目起作用本身），但不检测与边界的碰撞。例如，如果项目在 physicsView 之外，则无法进入。如果在内部，则无法退出。但它不会被算作碰撞（否则它总是碰撞）。

为了检测你的 rect 和你的 physicsView 之间的碰撞，你需要给 physicsView 一些物理属性。现在它只是一个普通的 UIView （参考视图）..

另一种解决必须为其赋予物理属性的方法是为其添加边界：

collisionBehavior.addBoundary(withIdentifier: "PhysicsViewBoundary" as NSString, for: UIBezierPath(rect: physicsView.bounds))

现在它将调用：

func collisionBehavior(_ behavior: UICollisionBehavior,
                       beganContactFor item: UIDynamicItem,
                       withBoundaryIdentifier identifier: NSCopying?,
                       at p: CGPoint) {
    print("began contact boundary")
}

func collisionBehavior(_ behavior: UICollisionBehavior,
                       endedContactFor item: UIDynamicItem,
                       withBoundaryIdentifier identifier: NSCopying?) {
    print("contact boundary ended")
}

未调用 UICollisionBehaviorDelegate 方法

UICollisionBehaviorDelegate methods not called

ios

uicollisionbehavior

uikit-dynamics

swift