手势方法(平移手势和滑动手势)之间是否有优先条件？

Question

我正在开发一个应用程序，其中我使用了平移手势以及滑动手势。所以每次我做划动手势的时候，都会调用来自平移手势的方法，而不会调用划动手势方法。

所有的手势方法之间有没有优先级？

Answer 1

您可以通过实现UIGestureRecognizerDelegate协议的以下方法来并行调用它们：

- (BOOL)gestureRecognizer:(UIPanGestureRecognizer *)gestureRecognizer 
shouldRecognizeSimultaneouslyWithGestureRecognizer:(UISwipeGestureRecognizer *)otherGestureRecognizer
{
    return YES;
}

Answer 2

在UIGestureRecognizer类上有一个名为"cancelsTouchesInView“的属性，它的默认值是YES。这将导致任何挂起的手势被取消。平移手势首先被识别，因为它不需要有"touch up“事件，所以它取消了Swipe手势。

如果您希望这两个手势都被识别，请尝试添加：

[yourPanGestureInstance setCancelsTouchesInView:NO];

Answer 3

优先使用swipe

您可以使用require(toFail:)方法为UIGestureRecognizer提供优先级。

@IBOutlet var myPanGestureRecognizer: UIPanGestureRecognizer!
@IBOutlet var mySwipeGestureRecognizer: UISwipeGestureRecognizer!

myPanGesture.require(toFail: mySwipeGestureRecognizer)

现在，您的pan将仅在您的刷卡失败时执行。

使用 pan everything

如果滑动和平移手势识别器在此设置中玩得不好，您可以将所有逻辑滚动到平移手势识别器中，以获得更多控制。

let minHeight: CGFloat = 100
let maxHeight: CGFloat = 700
let swipeVelocity: CGFloat = 500
var previousTranslationY: CGFloat = 0

@IBOutlet weak var cardHeightConstraint: NSLayoutConstraint!

@IBAction func didPanOnCard(_ sender: Any) {

    guard let panGesture = sender as? UIPanGestureRecognizer else { return }

    let gestureEnded = bool(panGesture.state == UIGestureRecognizerState.ended)
    let velocity = panGesture.velocity(in: self.view)

    if gestureEnded && abs(velocity.y) > swipeVelocity {
        handlePanOnCardAsSwipe(withVelocity: velocity.y)
    } else {
        handlePanOnCard(panGesture)
    }
} 

func handlePanOnCard(_ panGesture: UIPanGestureRecognizer) {

    let translation = panGesture.translation(in: self.view)
    let translationYDelta = translation.y - previousTranslationY

    if abs(translationYDelta) < 1 { return } // ignore small changes

    let newCardHeight = cardHeightConstraint.constant - translationYDelta

    if newCardHeight > minHeight && newCardHeight < maxHeight {
        cardHeightConstraint.constant = newCardHeight
        previousTranslationY = translation.y
    }

    if panGesture.state == UIGestureRecognizerState.ended {
        previousTranslationY = 0
    }
}

func handlePanOnCardAsSwipe(withVelocity velocity: CGFloat) {
    if velocity.y > 0 {
        dismissCard() // implementation not shown
    } else {
        maximizeCard() // implementation not shown
    }
}

下面是上述代码的实际应用演示。

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