使用 UIDynamicBehavior 向 UIView Pan 添加惯性

Question

我正在尝试使用 UIPanGestureRecognizer 平移“blockView”。当 pan 'Ended' 时，希望 'blockView' 以惯性减速，就像 UIScrollView 会以惯性结束滚动一样。

override func viewDidLoad() {
    super.viewDidLoad()
    self.dynamicAnimator = UIDynamicAnimator(referenceView: self.view)

    let collider = UICollisionBehavior(items: [self.magnifiedView!])
    collider.collisionDelegate = self
    collider.collisionMode = .Boundaries
    collider.translatesReferenceBoundsIntoBoundary = true
    self.dynamicAnimator.addBehavior(collider)

    self.dynamicProperties = UIDynamicItemBehavior(items: [self.magnifiedView!])
    //self.dynamicProperties.elasticity = 1.0
    //self.dynamicProperties.friction = 0.0
    self.dynamicProperties.allowsRotation = false
    //self.dynamicProperties.resistance = 10.0
    self.dynamicAnimator.addBehavior(self.dynamicProperties)

}


func panBlockView (panGesture: UIPanGestureRecognizer) {
    switch panGesture {
    case .Began:
        self.blockViewLocation = (self.blockView.center)!
    case .Changed:
        let translation = panGesture.translationInView(self.view)
        self.blockView.center = CGPointMake(self.blockViewLocation.x + translation.x, self.self.blockViewLocation.y + translation.y)
    case .Ended, .Cancelled:
        self.dynamicAnimator.addLinearVelocity(panGesture.velocityInView(self.view), forItem: self.blockView)
    }
}

问题： 当我平移视图时，“blockView”会尝试捕捉到平移起源的原点。当平移“结束”时，它会产生惯性，但它会从平移的原点开始（捕捉到平移原点后）。

注意： 上面的代码可以正常工作，只是为了 PAN THE VIEW。

Answer 1

添加一个捕捉行为并让它捕捉修复问题。