Get coordinates of multiple touches in Swift

Question

So I've been messing around trying to get the coordinates of touches on the screen. So far I can get the coordinates of one touch with this:

override func touchesBegan(touches: NSSet, withEvent event: UIEvent) {
    let touch = touches.anyObject()! as UITouch
    let location = touch.locationInView(self.view)
    println(location)
}

But when touching with two fingers I only get the coordinates of the first touch. Multi-touch works (I tested with this little tutorial: http://www.techotopia.com/index.php/An_Example_Swift_iOS_8_Touch,_Multitouch_and_Tap_Application). So my question is, how do I get the coordinates of the second (and third, fourth...) touch?

Para · Accepted Answer · 2017-10-08T15:22:42.680

15

** Updated to Swift 4 and Xcode 9 (8 Oct 2017) **

First of all, remember to enable multi-touch events by setting

self.view.isMultipleTouchEnabled = true

in your UIViewController's code, or using the appropriate storyboard option in Xcode:

Otherwise you'll always get a single touch in touchesBegan (see documentation here).

Then, inside touchesBegan, iterate over the set of touches to get their coordinates:

override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
    for touch in touches {
        let location = touch.location(in: self.view)
        print(location)
    }
}

edited Oct 08 '17 at 15:22

answered Feb 24 '15 at 13:15

Para

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Thank you for your answer! I marked giorashc's answer as most helpful because he gave slightly more information, but both methods work :) – Fr4nc3sc0NL Feb 24 '15 at 14:03
You're welcome! It's your call, of course :) I've edited the answer a little bit and left references to the documentation, underlining how it's important to enable multi-touch or the code won't work (we always forget about that!). I'm leaving this answer as a reference for other people who might need that detail :) – Para Feb 24 '15 at 14:37

score 4 · Answer 2 · answered Feb 24 '15 at 13:11

the given touches argument is a set of detected touches. You only see one touch because you select one of the touches with :

touches.anyObject() // Selects a random object (touch) from the set

In order to get all touches iterate the given set

for obj in touches.allObjects {
   let touch = obj as UITouch
   let location = touch.locationInView(self.view)
   println(location)
}

Christian · Answer 3 · 2015-02-24T13:16:26.290

1

You have to iterate over the different touches. That way you can access every touch.

for touch in touches{
  //Handle touch
  let touchLocation = touch.locationInView(self.view)
}

edited Feb 24 '15 at 13:16

answered Feb 24 '15 at 13:11

Christian

22,585
9
80
106

score 1 · Answer 4 · answered Sep 16 '15 at 12:11

1

In Swift 1.2 this has changed, and touchesBegan now provides a Set of NSObjects. To iterate through them, cast the touches collection as a Set of UITouch objects as follows:

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

    var touchSet = touches as! Set<UITouch>

    for touch in touchSet{
        let location = touch.locationInView(self.view)
        println(location)
    }
}

answered Sep 16 '15 at 12:11

Andrew

690
7
11

Should I mark this answer as answer to the question? (Since the now marked answer isn't really an answer anymore) – Fr4nc3sc0NL Sep 18 '15 at 08:26

Hawkydoky · Answer 5 · 2017-06-29T07:24:41.310

For Swift 3, based on @Andrew's answer :

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

    let touchSet = touches

    for touch in touchSet{
        let location = touch.location(in: self.view)
        print(location)
    }
}

EDIT, My bad, that's not answering your question, had the same problem and someone linked me to this previous answer :

Anyway, I had to change few things to make it works in swift 3, here is my current code :

var fingers = [String?](repeating: nil, count:5)

override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
    super.touchesBegan(touches, with: event)
    for touch in touches{
        let point = touch.location(in: self.view)
        for (index,finger)  in fingers.enumerated() {
            if finger == nil {
                fingers[index] = String(format: "%p", touch)
                print("finger \(index+1): x=\(point.x) , y=\(point.y)")
                break
            }
        }
    }
}

override func touchesMoved(_ touches: Set<UITouch>, with event: UIEvent?) {
    super.touchesMoved(touches, with: event)
    for touch in touches {
        let point = touch.location(in: self.view)
        for (index,finger) in fingers.enumerated() {
            if let finger = finger, finger == String(format: "%p", touch) {
                print("finger \(index+1): x=\(point.x) , y=\(point.y)")
                break
            }
        }
    }
}

override func touchesEnded(_ touches: Set<UITouch>, with event: UIEvent?) {
    super.touchesEnded(touches, with: event)
    for touch in touches {
        for (index,finger) in fingers.enumerated() {
            if let finger = finger, finger == String(format: "%p", touch) {
                fingers[index] = nil
                break
            }
        }
    }
}

I still have a little problem but I think it's linked to my GestureRecognizer in my code. But that should do the trick. It will print you the coordinate of each point in your consol.

If someone can confirm that this is working, I'll mark this as answer — Fr4nc3sc0NL, Jun 29 '17 at 01:57

score 0 · Answer 6 · answered Nov 29 '17 at 10:33

0

In Swift 3,4 Identify touch pointer by its hash:

// SmallDraw
func pointerHashFromTouch(_ touch:UITouch) -> Int {
    return Unmanaged.passUnretained(touch).toOpaque().hashValue
}

answered Nov 29 '17 at 10:33

SmallDraw

1

Get coordinates of multiple touches in Swift

6 Answers6

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