Question

我正在像在Tinder中一样开发卡片视图。当卡X原点大于我声明的值时，它移出屏幕。否则，它会再次居中。我正在UIPanGestureRecognizer函数中进行所有这些操作。我可以将视图移至Change状态。但是，有时它不会进入结束状态，因此卡既不会移出屏幕也不会再次居中。它只是停留在一些奇怪的地方。

所以我的问题是，卡片应该像下面的屏幕截图那样从屏幕上消失或粘在中间。

我在下面的帖子中尝试了解决方案，但是没有用：

UIPanGestureRecognizer not calling End state

UIPanGestureRecognizer does not switch to state "End" or "Cancel" if user panned x and y in negative direction

/// This method handles the swiping gesture on each card and shows the appropriate emoji based on the card's center.
@objc func handleCardPan(sender: UIPanGestureRecognizer) {

    // Ensure it's a horizontal drag
    let velocity = sender.velocity(in: self.view)
    if abs(velocity.y) > abs(velocity.x) {
        return
    }

    // if we're in the process of hiding a card, don't let the user interace with the cards yet
    if cardIsHiding { return }
    // change this to your discretion - it represents how far the user must pan up or down to change the option
    // distance user must pan right or left to trigger an option
    let requiredOffsetFromCenter: CGFloat = 80

    let panLocationInView = sender.location(in: view)
    let panLocationInCard = sender.location(in: cards[0])

    switch sender.state {
    case .began:
        dynamicAnimator.removeAllBehaviors()
        let offset = UIOffsetMake(cards[0].bounds.midX, panLocationInCard.y)
        // card is attached to center
        cardAttachmentBehavior = UIAttachmentBehavior(item: cards[0], offsetFromCenter: offset, attachedToAnchor: panLocationInView)
        //dynamicAnimator.addBehavior(cardAttachmentBehavior)
        let translation = sender.translation(in: self.view)
        print(sender.view!.center.x)
        sender.view!.center = CGPoint(x: sender.view!.center.x + translation.x, y: sender.view!.center.y)

        sender.setTranslation(CGPoint(x: 0, y: 0), in: self.view)
    case .changed:
        //cardAttachmentBehavior.anchorPoint = panLocationInView
        let translation = sender.translation(in: self.view)
        print(sender.view!.center.x)
        sender.view!.center = CGPoint(x: sender.view!.center.x + translation.x, y: sender.view!.center.y)
        sender.setTranslation(CGPoint(x: 0, y: 0), in: self.view)

    case .ended:

        dynamicAnimator.removeAllBehaviors()

        if !(cards[0].center.x > (self.view.center.x + requiredOffsetFromCenter) || cards[0].center.x < (self.view.center.x - requiredOffsetFromCenter)) {
            // snap to center
            let snapBehavior = UISnapBehavior(item: cards[0], snapTo: CGPoint(x: self.view.frame.midX, y: self.view.frame.midY + 23))
            dynamicAnimator.addBehavior(snapBehavior)
        } else {
            let velocity = sender.velocity(in: self.view)
            let pushBehavior = UIPushBehavior(items: [cards[0]], mode: .instantaneous)
            pushBehavior.pushDirection = CGVector(dx: velocity.x/10, dy: velocity.y/10)
            pushBehavior.magnitude = 175
            dynamicAnimator.addBehavior(pushBehavior)

            // spin after throwing
            var angular = CGFloat.pi / 2 // angular velocity of spin
            let currentAngle: Double = atan2(Double(cards[0].transform.b), Double(cards[0].transform.a))

            if currentAngle > 0 {
                angular = angular * 1
            } else {
                angular = angular * -1
            }
            let itemBehavior = UIDynamicItemBehavior(items: [cards[0]])
            itemBehavior.friction = 0.2
            itemBehavior.allowsRotation = true
            itemBehavior.addAngularVelocity(CGFloat(angular), for: cards[0])
            dynamicAnimator.addBehavior(itemBehavior)

            showNextCard()
            hideFrontCard()

        }
    default:
        break
    }
}

Answer 1

我正在检查是否要在水平方向滑动：

let velocity = sender.velocity(in: self.view)
if abs(velocity.y) > abs(velocity.x) {
    return
}

由于某种原因，我在水平滑动时正要返回。当我评论此代码块时，一切开始起作用：）

UIPanGestureRecognizer有时无法进入最终状态

1 个答案: