UICollisionBehavior

Question

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

现在我可以使用可拖动视图来推动较小的视图。

问题： 如果我将一个较小的视图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。我用来点击和推动其他视图的 "hammer view" 也会陷入边界。 IE。它 stuck/un-draggable 靠在屏幕的一侧。

我做了一个非常小的例子，看看当我只有很少的视图并且没有冲突的行为时，我是否可以重现它，视图仍然穿过边界。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。你的锤子将视图推向参考边界，直到它最终突破，因为你的模型的物理学说它应该这样做。参考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。

这并没有真正的记录，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，在你的情况下（就像我的情况一样）如果一个项目在初始化后超出边界，它的行为也是未定义的。

我试图在视图的右侧排列一组球。最右边的球下面有一个锚点。黄色视图是参考视图，一切都很好......

但是，当我添加更多的球到它们不再适合的位置时，它们就会开始弹出。事实上，图像右上角的那个从底部中心弹出并逆时针围绕参考视图滚动到锚点附近。

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，然后将您的视图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))

UICollisionBehavior - 视图穿过边界

UICollisionBehavior - views pass through boundaries

ios

uikit-dynamics

swift

ios8.1