UISwipeGestureRecognizer Swipe length

Question

Any idea if there is a way to get the length of a swipe gesture or the touches so that i can calculate the distance?

Answer 1

I have an implementation similar to the answer in swift that discriminates between a drag and a swipe calculating the distance relative to the container and the speed of the swipe.

@objc private func handleSwipe(sender: UIPanGestureRecognizer) {
    if (sender.state == .began) {
        self.swipeStart.location = sender.location(in: self)
        self.swipeStart.time = Date()
    }
    else if (sender.state == .ended) {
        let swipeStopLocation : CGPoint = sender.location(in: self)
        let dx : CGFloat = swipeStopLocation.x - swipeStart.location.x
        let dy : CGFloat = swipeStopLocation.y - swipeStart.location.y
        let distance : CGFloat = sqrt(dx*dx + dy*dy );
        let speed : CGFloat = distance / CGFloat(Date().timeIntervalSince(self.swipeStart.time))
        let portraitWidth = min(self.frame.size.width, self.frame.size.height)
        print("Distance: \(distance), speed: \(speed), dy: \(dy), dx: \(dx), portraitWidth: \(portraitWidth), c1: \(distance >  portraitWidth * 0.4), c2: \(abs(dy) < abs(dx) * 0.25), c3: \(speed > portraitWidth * 3.0) ")
        if distance >  portraitWidth * 0.4 && abs(dy) < abs(dx) * 0.25 && speed > portraitWidth * 3.0 {
            if dx > 0 {
                delegate?.previousAssetPressed(self)
            }else{
                delegate?.nextAssetPressed(self)
            }
        }
    }
}

Answer 2

For those of us using Xamarin:

void panGesture(UIPanGestureRecognizer gestureRecognizer) {
    if (gestureRecognizer.State == UIGestureRecognizerState.Began) {
        startLocation = gestureRecognizer.TranslationInView (view)
    } else if (gestureRecognizer.State == UIGestureRecognizerState.Ended) {
        PointF stopLocation = gestureRecognizer.TranslationInView (view);
        float dX = stopLocation.X - startLocation.X;
        float dY = stopLocation.Y - startLocation.Y;
        float distance = Math.Sqrt(dX * dX + dY * dY);
        System.Console.WriteLine("Distance: {0}", distance);
    }
}

Answer 3

In Swift

 override func viewDidLoad() {
    super.viewDidLoad()

    // add your pan recognizer to your desired view
    let panRecognizer = UIPanGestureRecognizer(target: self, action:  #selector(panedView))
    self.view.addGestureRecognizer(panRecognizer)

}

   @objc func panedView(sender:UIPanGestureRecognizer){
        var startLocation = CGPoint()
        //UIGestureRecognizerState has been renamed to UIGestureRecognizer.State in Swift 4
        if (sender.state == UIGestureRecognizer.State.began) {
            startLocation = sender.location(in: self.view)
        }
        else if (sender.state == UIGestureRecognizer.State.ended) {
            let stopLocation = sender.location(in: self.view)
            let dx = stopLocation.x - startLocation.x;
            let dy = stopLocation.y - startLocation.y;
            let distance = sqrt(dx*dx + dy*dy );
            NSLog("Distance: %f", distance);

        if distance > 400 {
            //do what you want to do
        }
    }
}

Hope that helps all you Swift pioneers

Answer 4

It's impossible to get a distance from a swipe gesture, because the SwipeGesture triggers the method where you could access the location exactly one time, when the gesture has ended.
Maybe you want to use a UIPanGestureRecognizer.

If it possible for you to use pan gesture you would save the starting point of the pan, and if the pan has ended calculate the distance.

- (void)panGesture:(UIPanGestureRecognizer *)sender {
    if (sender.state == UIGestureRecognizerStateBegan) {
        startLocation = [sender locationInView:self.view];
    }
    else if (sender.state == UIGestureRecognizerStateEnded) {
        CGPoint stopLocation = [sender locationInView:self.view];
        CGFloat dx = stopLocation.x - startLocation.x;
        CGFloat dy = stopLocation.y - startLocation.y;
        CGFloat distance = sqrt(dx*dx + dy*dy );
        NSLog(@"Distance: %f", distance);
    }
}

Answer 5

You can only do it a standard way: remember the touch point of touchBegin and compare the point from touchEnd.

Answer 6

func swipeAction(gesture: UIPanGestureRecognizer) {
    let transition = sqrt(pow(gesture.translation(in: view).x, 2)
                     + pow(gesture.translation(in: view).y, 2))
}