ios - UICollisionBehavior - View 穿过边界

Question

作为实现 UICollisionBehaviour 的一部分，我为屏幕边缘设置了边界。然后我添加了一些 View ，最后将 UIPanGestureRecognizer 附加到其中一个。

现在我可以使用可拖动 View 来插入较小的 View 。

问题:如果我将一个较小的 View 转角并继续将其推向屏幕边缘，它最终会滑过边界并被困在另一侧。我用来击打和插入其他 View 的“锤 subview ”也会陷入边界。 IE。它被卡在/不可拖动到屏幕的一侧。

我做了一个非常小的例子，看看当我只有很少的 View 并且没有冲突的行为时，我是否可以重现它， View 仍然穿过边界。要么 UIDynamics 不能处理太多，要么(更有可能)我以某种方式配置错误。

下面的小例子有奇怪的行为:

class ViewController: UIViewController {

var animator: UIDynamicAnimator?
var collisionBehaviour: UICollisionBehavior?
var panBehaviour: UIAttachmentBehavior?

override func viewDidLoad() {
    super.viewDidLoad()
}

override func viewWillAppear(animated: Bool) {
    super.viewWillAppear(animated)
    setup()
}

func setup() {
    //setup collisionBehaviour and animator
    collisionBehaviour = UICollisionBehavior()
    collisionBehaviour!.collisionMode = UICollisionBehaviorMode.allZeros
    animator = UIDynamicAnimator(referenceView: view)

    //add boundaries
    collisionBehaviour!.addBoundaryWithIdentifier("verticalMin", fromPoint: CGPointMake(0, 0), toPoint: CGPointMake(0, CGRectGetHeight(view.frame)))
    collisionBehaviour!.addBoundaryWithIdentifier("verticalMax", fromPoint: CGPointMake(CGRectGetMaxX(view.frame), 0), toPoint: CGPointMake(CGRectGetMaxX(view.frame), CGRectGetHeight(view.frame)))
    collisionBehaviour!.addBoundaryWithIdentifier("horizontalMin", fromPoint: CGPointMake(0, CGRectGetMaxY(view.frame)), toPoint: CGPointMake(CGRectGetMaxX(view.frame), CGRectGetMaxY(view.frame)))
    collisionBehaviour!.addBoundaryWithIdentifier("horizontalMax", fromPoint: CGPointMake(0, 0), toPoint: CGPointMake(CGRectGetMaxX(view.frame), 0))

    //        collisionBehaviour!.translatesReferenceBoundsIntoBoundary = true // same effect as the above boundaries
    //setup up some round views to push around
    for i in 0..<5 {
        let ball = UIView(frame: CGRectMake(0, 30, 50, 50))
        ball.center = view.center
        ball.backgroundColor = UIColor.greenColor()
        ball.layer.cornerRadius = CGRectGetWidth(ball.frame) * 0.5
        view.addSubview(ball)
        collisionBehaviour!.addItem(ball)
    }

    //setup a hammer view which can be dragged and used to squeze the ball views of the screen
    let hammer = UIView(frame: CGRectMake(0, 0, 100, 100))
    hammer.backgroundColor = UIColor.redColor()
    view.addSubview(hammer)
    collisionBehaviour!.addItem(hammer)

    let noRotationBehaviour = UIDynamicItemBehavior(items: [hammer])
    noRotationBehaviour.allowsRotation = false
    animator!.addBehavior(noRotationBehaviour)

    let panGestureRecognizer = UIPanGestureRecognizer(target: self, action: Selector("handlePan:"))
    hammer.addGestureRecognizer(panGestureRecognizer)

    //"start" the collision detection
    animator!.addBehavior(collisionBehaviour!)
}

//Move the hammer around
func handlePan(recognizer: UIPanGestureRecognizer) {
    if let view = recognizer.view {
        let location = recognizer.locationInView(self.view)
        switch recognizer.state {
        case .Began:
            panBehaviour = UIAttachmentBehavior(item: view, attachedToAnchor: location)
            animator!.addBehavior(panBehaviour!)
            println("begin")
        case .Changed:
            panBehaviour!.anchorPoint = location
            println("change \(location)")
        case .Ended:
            println("ended")
            animator!.removeBehavior(panBehaviour!)
        default:
            println("done")
        }
    }
}

override func didReceiveMemoryWarning() {
    super.didReceiveMemoryWarning()
    // Dispose of any resources that can be recreated.
}

感谢您提供的任何帮助。

Answer 1

好消息:您没有做错任何事。坏消息:这是预期的行为。你的锤子将 View 推向引用边界，直到它最终突破，因为你的模型的物理学说它应该这样做。引用边界不是不能跨越的边界，它只是定义了你的物理规则始终适用的区域。

这并没有真正记录下来，但 UICollisionBehavior 的页面指出:

When setting the initial position for a dynamic item, you must ensure that its bounds do not intersect any collision boundaries. The animation behavior for such a misplaced item is undefined.

这只是部分正确，在您的情况下(与我的情况一样)如果项目在初始化后超出边界，它的行为也是未定义的。

我试图在 View 的右侧安排一组球。最右边的球下面有一个 anchor 。黄色 View 是引用 View ，一切都很好......

但是，当我添加更多球到它们不再适合时，它们会开始弹出。事实上，图像右上角的那个从底部中心弹出并逆时针围绕引用 View 滚动到 anchor 附近。

更新:对于解决方案，您可以设置 collisionBehaviors 的 collisionDelegate 并捕获碰撞的开始和结束，然后将您的 View 移回边界并远离您的锤子，使其看起来像是逃脱了。

如您所知，translatesReferenceBoundsIntoBoundary 等同于一组 addBoundaryWithIdentifier 调用。

使用:

collisionBehaviour!.translatesReferenceBoundsIntoBoundary = true 

同于:

//add boundaries
    collisionBehaviour!.addBoundaryWithIdentifier("verticalMin", fromPoint: CGPointMake(0, 0), toPoint: CGPointMake(0, CGRectGetHeight(view.frame)))
    collisionBehaviour!.addBoundaryWithIdentifier("verticalMax", fromPoint: CGPointMake(CGRectGetMaxX(view.frame), 0), toPoint: CGPointMake(CGRectGetMaxX(view.frame), CGRectGetHeight(view.frame)))
    collisionBehaviour!.addBoundaryWithIdentifier("horizontalMin", fromPoint: CGPointMake(0, CGRectGetMaxY(view.frame)), toPoint: CGPointMake(CGRectGetMaxX(view.frame), CGRectGetMaxY(view.frame)))
    collisionBehaviour!.addBoundaryWithIdentifier("horizontalMax", fromPoint: CGPointMake(0, 0), toPoint: CGPointMake(CGRectGetMaxX(view.frame), 0))