How to detect that multiple UIGestureRecognizers end? - ios

Question

in my view I have multiple gesture recognizers (UIPanGestureRecognizer, UIPinchGestureRecognizer and UIRotationGestureRecognizer) and I allowed them to detect touches simultaneously:
func gestureRecognizer(_ gestureRecognizer: UIGestureRecognizer,
shouldRecognizeSimultaneouslyWith otherGestureRecognizer: UIGestureRecognizer) -> Bool {
if gestureRecognizer.view != otherGestureRecognizer.view {
return false
}
return true
}
The problem with this approach is that I am no longer able to detect when all the 3 gestures end. I cannot use
if gesture.state == .ended || gesture.state == .cancelled {
}
bacause this is valid only for a gesture recognizer and not for the all 3.
Any idea if there an api to detect when all active recognizers end?
Thanks
Solution
This works but it is very ugly: basically I keep track when all three gestures recognizers end and prevent to detect the end multiple times as the recognizers callback can be called in any order:
class SCCanvasViewController: UIViewController {
var gesturesAlreadyEnded = false
lazy var panGestureRecognizer: UIPanGestureRecognizer = {
let gr = UIPanGestureRecognizer(target: self, action: #selector(handlePan(_:)))
gr.delegate = self
return gr
}()
lazy var pinchGestureRecognizer: UIPinchGestureRecognizer = {
let gr = UIPinchGestureRecognizer(target: self, action: #selector(handlePinch(_:)))
gr.delegate = self
return gr
}()
lazy var rotateGestureRecognizer: UIRotationGestureRecognizer = {
let gr = UIRotationGestureRecognizer(target: self, action: #selector(handleRotation(_:)))
gr.delegate = self
return gr
}()
override func viewDidLoad() {
super.viewDidLoad()
view.addGestureRecognizer(panGestureRecognizer)
view.addGestureRecognizer(pinchGestureRecognizer)
view.addGestureRecognizer(rotateGestureRecognizer)
}
func isGestureEnded(gesture: UIGestureRecognizer) -> Bool {
return gesture.state == .ended || gesture.state == .cancelled || gesture.state == .failed
}
func allGesturesEnded() -> Bool {
let panEnded = isGestureEnded(gesture: panGestureRecognizer)
let pinchEnded = isGestureEnded(gesture: pinchGestureRecognizer)
let rotationEnded = isGestureEnded(gesture: rotateGestureRecognizer)
return panEnded && pinchEnded && rotationEnded
}
#objc func handlePan(_ gesture: UIPanGestureRecognizer) {
if gesture.state == .began {
gesturesAlreadyEnded = false
}
if !gesturesAlreadyEnded && isGestureEnded(gesture: gesture) {
canvasView.showHorizontalSnapIndicators(areVisible: false)
canvasView.showVerticalSnapIndicators(areVisible: false)
if (allGesturesEnded()) {
gesturesAlreadyEnded = true
print("Can create transformation command")
}
return
}
}
#objc func handlePinch(_ gesture: UIPinchGestureRecognizer) {
if gesture.state == .began {
gesturesAlreadyEnded = false
}
if !gesturesAlreadyEnded && isGestureEnded(gesture: gesture) {
if (allGesturesEnded()) {
gesturesAlreadyEnded = true
print("Can create transformation command")
}
return
}
}
#objc func handleRotation(_ gesture: UIRotationGestureRecognizer) {
if gesture.state == .began {
gesturesAlreadyEnded = false
}
if !gesturesAlreadyEnded && isGestureEnded(gesture: gesture) {
if (allGesturesEnded()) {
gesturesAlreadyEnded = true
print("Can create transformation command")
}
return
}
}
}
extension SCCanvasViewController: UIGestureRecognizerDelegate {
func gestureRecognizer(_ gestureRecognizer: UIGestureRecognizer,
shouldRecognizeSimultaneouslyWith otherGestureRecognizer: UIGestureRecognizer) -> Bool {
if gestureRecognizer.view != otherGestureRecognizer.view {
return false
}
return true
}
}

Answer 1

Set it up to get multi-touch notifications, then examine the set of touches impacted by the event.
class TouchableView: UIView {
var touchViews = [UITouch:TouchSpotView]()
override init(frame: CGRect) {
super.init(frame: frame)
isMultipleTouchEnabled = true
}
required init?(coder aDecoder: NSCoder) {
super.init(coder: aDecoder)
isMultipleTouchEnabled = true
}
override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
for touch in touches {
createViewForTouch(touch: touch)
}
}
override func touchesMoved(_ touches: Set<UITouch>, with event: UIEvent?) {
for touch in touches {
let view = viewForTouch(touch: touch)
// Move the view to the new location.
let newLocation = touch.location(in: self)
view?.center = newLocation
}
}
override func touchesEnded(_ touches: Set<UITouch>, with event: UIEvent?) {
for touch in touches {
removeViewForTouch(touch: touch)
}
}
override func touchesCancelled(_ touches: Set<UITouch>, with event: UIEvent?) {
for touch in touches {
removeViewForTouch(touch: touch)
}
}
// Other methods. . .
}