Creating a UIView with PanGestureRecognizer and activating it without lifting the finger

Question

I've created a circle on the screen by creating a UIView at the finger's location when touchesBegan():

In ViewController:

override func touchesBegan(touches: Set<UITouch>, withEvent event: UIEvent?) {

    for touch in touches {

        let pos = touch.locationInView(view)

        let radius: CGFloat = touch.majorRadius * 2
        let circleView = CircleView(frame: CGRectMake(pos.x - radius / 2, pos.y - radius / 2, radius, radius))
        view.addSubview(circleView)

    }
}

In CircleView:

override init(frame: CGRect) {
    super.init(frame: frame)

    let recognizer = UIPanGestureRecognizer(target: self, action: Selector("handlePan:"))
    recognizer.delegate = self
    self.addGestureRecognizer(recognizer)

}

This creates the circle, but does not move it immediately when I move my finger. Instead, I have to pick my finger up and place it back on the circle before handlePan() kicks in.

Is there a way to start tracking a pan gesture without lifting the finger that spawned it's parent view, taking into account there may be multiple fingers touching and moving around the screen?

Answer 1

The issue here is that you're using both touchesBegan, and a UIPanGestureRecognizer. For best results, use one or the other. If you're going to do it with just a pan gesture (which is what I would do), do the following:

func handlePan(gesture: UIPanGestureRecognizer) {
    if gesture.state == UIGestureRecognizerState.Began {
        //handle creating circle
    } else if gesture.state == UIGestureRecognizerState.Changed {
        //handle movement
    }
}

Hope this helps!

Answer 2

If you have already created the circle view successfully in method touchesBegan:withEvent:

you can

1. Make that circle view a property

2. Move that circle view directly in method touchesMoved:withEvent:

This won't require you pick your finger up first

Answer 3

I was able to accomplish multiple independent touches by keeping a dictionary of all active touches and creating the circle views in touchesBegan() and updating their position in touchesMoved() by querying that dictionary.

var fingerTouches = [UITouch: CircleView]()

override func touchesBegan(touches: Set<UITouch>, withEvent event: UIEvent?) {

    for touch in touches {

        let pos = touch.locationInView(view)

        let radius: CGFloat = touch.majorRadius * 2
        let circle = CircleView(frame: CGRectMake(pos.x - radius / 2, pos.y - radius / 2, radius, radius))
        view.addSubview(circle)

        fingerTouches[touch] = circle

    }
}

override func touchesMoved(touches: Set<UITouch>, withEvent event: UIEvent?) {

    for touch in touches {

        let pos = touch.locationInView(view)

        let radius: CGFloat = touch.majorRadius * 2
        fingerTouches[touch]!.frame = CGRectMake(pos.x - radius / 2, pos.y - radius / 2, radius, radius)

    }

}

override func touchesEnded(touches: Set<UITouch>, withEvent event: UIEvent?) {

    for touch in touches {
        fingerTouches[touch]!.removeFromSuperview()
    }
}