Access the velocity of a pan gesture

问题

I want to get the velocity of a pan gesture, and I thought to use the sender's velocity property, but it doesn't seem to work:

@IBAction func handleGesture(sender: AnyObject) {
    let v = sender.velocity
}

but it throws an error saying :

"ambiguous use of 'velocity'"

If that's not the way to access the velocity of a pan gesture, what is?

回答1:

UIPanGestureRecognizer does not have property named velocity. You should use velocityInView method.

func userPanned(sender: UIPanGestureRecognizer) {
    let v = sender.velocityInView(self.view)
}

回答2:

For velocity, you need to do the following

sender.velocityInView(self.view) gives you the pixels. Inorder to get the velocity, you need to divide it by 60 like this:

sender.velocityInView(self.view).x / 60 - For horizontal

sender.velocityInView(self.view).y / 60 - For vertical

Hence, you can update the position just by adding it with your initial value like this:

var initialLocation: CGPoint? -> Global

initialLocation.x = (initialLocation ?? 0)

(initialLocation.x)! = (initialLocation.x)! + (sender.velocity(in: colorSlider!).x / 60) - For horizontal

(initialLocation.y)! = (initialLocation.y)! + (sender.velocity(in: colorSlider!).y / 60) - For vertical

Thanks.

来源：https://stackoverflow.com/questions/26748219/access-the-velocity-of-a-pan-gesture