why is there a delay when moving object using UIPanGestureRecognizer

Question

I\'m moving UIView object using UIPanGestureRecognizer - how much I drag my finger on screen, that much I move the view in the same direction (only in X - left or right, Y is no

Answer 1

The GestureRecognizer can't be sure, if it is a pan gesture, before you moved your finger some pixels. I don't know the exact tolerance value, but that is why you feel a delay.

Documentation:

A panning gesture is continuous. It begins when the minimum number of fingers allowed have moved enough to be considered a pan.

If you want instant movement, you probably need to build your own logic using touchesMoved:.

Another approach could be, to animate to the first recognized point. But that doesn't remove the delay. For that approach you could have a look at my JDDroppableView on github.

Answer 2

Use a UILongPressGestureRecognizer and set the minimumPressDuration to 0.0. This recognizes instantly and you get all the same updates including the UIGestureRecognizerStateChanged with the updated location.

Answer 3

I found that it was faster responding if you use just regular touchesBegan, Moved and Ended. I even subclassed a UIGestureRecognizer, and it still had lag on the panning gesture. Even though the touchesBegan within the UIGestureRecognizer would trigger on time, the state change would take a half second to change its state... It seems faster to just use a plain old TouchesBegan, especially if you're cpu is doing a lot.

override func touchesBegan(touches: Set<UITouch>, withEvent event: UIEvent?)
{
    if touches.count == 1
    {
        initialTouchLocation = (touches.first?.locationInView(self).x)!
    }
}
override func touchesMoved(touches: Set<UITouch>, withEvent event: UIEvent?)
{
    if touches.count == 1
    {
        let locationInView = touches.first?.locationInView(self)
        if !thresholdHit
        {
            //this is the threshold for x movement in order to trigger the panning...
            if abs(initialTouchLocation - locationInView!.x) > 1
            {
                thresholdHit = true
            }
        }
        else
        {
            if (self.frame.width != CGFloat(screenSize))
            {
                let panDelta = initialTouchLocation - locationInView!.x
            }
        }
    }
}