SpriteKit tracking multiple touches - swift

Question

I have several buttons that move a main character. (Left, right, jump, etc.) But, when I touch more than one button at a time, the previous one is ended. My question is, how do I keep both touches alive for the duration of their touches? As an example, this would allow the character to move forward and jump at the same time. I have set multipleTouchEnabled to true. I've read that using a dictionary to track touches would help, but I can't seem to wrap my head around the implementation.
override func touchesBegan(touches: Set<UITouch>, withEvent event: UIEvent?) {
for touch in touches {
let location = touch.locationInView(nil)
if location.x < self.size.width / 2 && location.y > self.size.height / 2 {
movingLeft = true
}
if location.x > self.size.width / 2 && location.y > self.size.height / 2 {
movingRight = true
}
if location.x < self.size.width / 2 && location.y < self.size.height / 2 {
jump()
}
if location.x > self.size.width / 2 && location.y < self.size.height / 2 {
jump()
}
}
}
override func touchesEnded(touches: Set<UITouch>, withEvent event: UIEvent?) {
movingLeft = false
movingRight = false
}
func jump() {
mainCharacter.physicsBody?.velocity = CGVector(dx: 0, dy: 0)
mainCharacter.physicsBody?.applyImpulse(CGVector(dx: 0, dy: 400))
}

Answer 1

The logic
You should create a dictionary of active touches.
private var activeTouches = [UITouch:String]()
Every time a touch begins you save it into the dictionary and assign to it a label.
activeTouches[touch] = "left"
So when the touch does end you can search for it into your dictionary and find the related label. Now you know which button has been released by the user.
let button = activeTouches[touch]
if button == "left" { ... }
And don't forget to remove it from the dictionary.
activeTouches[touch] = nil
The implementation
class GameScene: SKScene {
private var activeTouches = [UITouch:String]()
override func touchesBegan(touches: Set<UITouch>, withEvent event: UIEvent?) {
for touch in touches {
let button = findButtonName(from:touch)
activeTouches[touch] = button
tapBegin(on: button)
}
}
override func touchesEnded(touches: Set<UITouch>, withEvent event: UIEvent?) {
for touch in touches {
guard let button = activeTouches[touch] else { fatalError("Touch just ended but not found into activeTouches")}
activeTouches[touch] = nil
tapEnd(on: button)
}
}
private func tapBegin(on button: String) {
print("Begin press \(button)")
// your custom logic goes here
}
private func tapEnd(on button:String) {
print("End press \(button)")
// your custom logic goes here
}
private func findButtonName(from touch: UITouch) -> String {
// replace this with your custom logic to detect a button location
let location = touch.locationInView(self.view)
if location.x > self.view?.frame.midX {
return "right"
} else {
return "left"
}
}
}
In the code above you should put your own code into
tapBegin: this method receive the label of a button and start some action.
E.g. start running.
tapEnd: this method receive the label of a button and stop some action.
E.g. stop running.
findButtonName: this method receives a UITouch and returns the label of the button pressed by the user.
Test
I tested the previous code on my iPhone. I performed the following actions.
started pressing the right of the screen
started pressing the left of the screen
removed finger from the right of the screen
removed finger from the left of the screen
As you can see in the following log the code is capable of recognizing different touches
Begin press right
Begin press left
End press right
End press left
Conclusion
I hope I made myself clear. Let me know if something is not.

Answer 2

Issue
For me it was a bit foolish but there's an option that I miss to enable in my storyboard in order to handle multiple touch in my GameScene of type SKScene.
When one of the overwritten functions is being called, you should have more than 1 touch contained in touches.
Those functions are indeed:
touchesBegan
touchesMoved
touchesEnded
touchesCancelled
... and the way to retrieve the touches is indeed to browse through them. However, if you are only able to retrieve one touch only, follow the steps bellow.
Debugging
Here's what you can do to see if you have multiple touches in your set of touches:
override func touchesMoved(_ touches: Set<UITouch>, with event: UIEvent?) {
for (i, t) in touches.enumerated() {
print(i, t.location(in: self))
self.touchMoved(toPoint: t.location(in: self))
}
}
Output:
There you should find a 0 for the first touch and a 1 when you touch with 2 fingers... and so on.
Solution
I case you encounter the same problem than me and have only the touch t at index 0 but no other touch, you should see upper in the hierarchy of views if all of them are enabled for multi-touch. In my case it was the view containing the GameScene of type SKScene that did not have the option Multiple Touch enabled. See below: