ios - Swift - UICollisionBehavior 委托(delegate)方法未被调用

Question

我正在做一个简单的动画，它需要我处理一些与边界的碰撞。

我有一个类 viewcontroller，我将其扩展为 UICollisionBehaviorDelegate，以便我可以识别和处理 View 冲突。

出于某种原因，当发生冲突时，我的委托(delegate)方法永远不会触发。

class ViewController: UIViewController {

    var fallingImageViews: [UIImageView]!
    var downAnimator: UIDynamicAnimator!

    override func viewDidLoad() {
        super.viewDidLoad()

        //imagine fallingImageViews Initializers happening here

        downAnimator = initializeAnimators()
    }

    func initializeAnimators() -> UIDynamicAnimator {
        let downwardAnimator = UIDynamicAnimator(referenceView: self.view)

        downwardAnimator.addBehavior(setBoundaries())
        downwardAnimator.addBehavior(setGravity())
        downwardAnimator.addBehavior(setBounciness())
        downwardAnimator.delegate = self

        return downwardAnimator
    }

    func setBoundaries() -> UICollisionBehavior {
        let boundaries = UICollisionBehavior(items: fallingImageViews)
        boundaries.collisionDelegate = self

        // prevent collisions between items
        boundaries.collisionMode = .boundaries

        boundaries.setTranslatesReferenceBoundsIntoBoundary = true

        return boundaries
    }
}

// MARK: Collision Behavior Delegate
extension ViewController: UICollisionBehaviorDelegate, UIDynamicAnimatorDelegate {

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

Answer 1

我完全废弃了旧答案并更新了它。很抱歉误导了您，但这是我修改后的答案:

这个想法是，您向想要动画的对象添加行为(在您的例子中，您的 fallingImageViews)。

因此，这里的所有代码实际上都应该进入一个继承自 UIImageView 的类(在我的示例代码中，您会看到我继承自 CardCtrl 对象，但它也可能是 UIImageView)。

您需要做的唯一更改是您的 UIDynamicAnimator 的引用 View 必须是 superview 并且所有动画行为的所有引用 View 都设置为[自己]。

这是我的一个旧项目中的一些示例代码:

@IBDesignable class SlidingCard: CardCtrl, UICollisionBehaviorDelegate
{
   ...
    //MARK: - Private Properties

    private var gripHeightAnch: NSLayoutConstraint = NSLayoutConstraint()
    private var animator: UIDynamicAnimator!
    private var dynamicItem: UIDynamicItemBehavior!
    private var collisionBnds: UICollisionBehavior!
    private var snap: UISnapBehavior!
    private var botBndryPt: CGFloat!
    private var gravity: UIGravityBehavior!
    private var pan: UIPanGestureRecognizer!

    ...

    //MARK: - Delegate Methods

    func collisionBehavior(_ behavior: UICollisionBehavior, beganContactFor item: UIDynamicItem,
                           withBoundaryIdentifier identifier: NSCopying?, at p: CGPoint)
    {
        guard let identifier = identifier else {return}
        if String(describing: identifier) == "bot"
        {
            sendActions(for: .touchDragOutside)
        }
        else
        {
            sendActions(for: .touchDragInside)
        }
    }

    ...

    //MARK: - Private Setup Methods

    private func defineSlideBehavior()
    {
        if animator == nil
        {
            animator = UIDynamicAnimator(referenceView: superview!)
        }
        animator!.removeAllBehaviors()

        //Check to see if behaviors are already installed because .removeAllBehaviors() doesn't
        //always work
        var addItem = true
        var addBounds = true
        var addGravity = true
        for blarHar in animator!.behaviors
        {
            if blarHar.isKind(of: UIDynamicItem.self)
            {
                addItem = false
            }
            if blarHar.isKind(of: UICollisionBehavior.self)
            {
                addBounds = false
            }
            if blarHar.isKind(of: UIGravityBehavior.self)
            {
                addGravity = false
            }
        }
        //Make it so the card doesn't wobble
        if dynamicItem == nil && addItem
        {
            dynamicItem = UIDynamicItemBehavior(items: [self])
            dynamicItem.allowsRotation = false
            dynamicItem.elasticity = 0
        }
        animator!.addBehavior(dynamicItem)

        //Add two boundaries for the drawer to collide with
        if collisionBnds == nil && addBounds
        {
            collisionBnds = UICollisionBehavior(items: [self])
            collisionBnds.collisionDelegate = self
        }
        botBndryPt = frame.maxY * 2 + 1.5
        collisionBnds.removeAllBoundaries()
        collisionBnds.addBoundary(withIdentifier: "top" as NSCopying,
                                  from: CGPoint(x: frame.minX, y: frame.minY - 1.5),
                                  to: CGPoint(x: frame.maxX, y: frame.minY - 1.5))
        collisionBnds.addBoundary(withIdentifier: "bot" as NSCopying,
                                  from: CGPoint(x: frame.minX, y: botBndryPt),
                                  to: CGPoint(x: frame.maxX, y: botBndryPt))
        animator!.addBehavior(collisionBnds)

        //Define the initial gravity that affects the drawer
        if addGravity
        {
            gravity = UIGravityBehavior(items: [self])
            gravity.gravityDirection = CGVector(dx: 0, dy: -gravityStrength)
            animator!.addBehavior(gravity)
        }
    }
}