Avoid button touches to be registered as swipe.

Question

 using UnityEngine;
 using System.Collections;
 
 public class TouchEventManager : MonoBehaviour {
 
     public float MinimumSwipeDist;
     public float ThresholdAngle;
     public delegate void GestureEventHandler();
     public static event GestureEventHandler OnSwipeRight;
     public static event GestureEventHandler OnSwipeLeft;
     public static event GestureEventHandler OnSwipeUp;
     public static event GestureEventHandler OnSwipeDown;
 
     private Vector2 mStartPos;
     
     // Update is called once per frame
     void Update () {
         if (Input.touchCount > 0) {
             Touch touch = Input.touches[0];
             
             switch(touch.phase) {
             case TouchPhase.Began:
                 mStartPos = touch.position;
                 break;
                 
             case TouchPhase.Ended:
                 float swipeDist = (touch.position - mStartPos).magnitude;
                 // check if legal swipe
                 if(swipeDist > MinimumSwipeDist) {
                     determineSwipeType(touch.position);
                 }
                 break;
             }
         }
     }
 
     void determineSwipeType(Vector2 endPosition) {
         float angle = Vector2.Angle (Vector2.right, (endPosition - mStartPos));
 
         if (angle < ThresholdAngle) {
             // right swipe
             if(OnSwipeRight != null) {
                 OnSwipeRight();
             }
         } else if(angle >= ThresholdAngle && angle <= 180 - ThresholdAngle) {
             float swipeValue = Mathf.Sign(endPosition.y - mStartPos.y);
             if(swipeValue > 0) {
                 // up swipe
                 if(OnSwipeUp != null) {
                     OnSwipeUp();
                 }
             } else {
                 // down swipe
                 if(OnSwipeDown != null) {
                     OnSwipeDown();
                 }
             }
         } else if(angle >= 180 - ThresholdAngle){
             // left swipe
             if(OnSwipeLeft != null) {
                 OnSwipeLeft();
             }
         }
     }
 }

I have the above code to detect swipe gesture in my game. I recently implemented some UI using the new UI system introduced in v4.6. I have a pause/resume button during gameplay and when I click on the buttons and make a small swipe motion while clicking, my swipe gesture code registers it and affects the gameplay. I have read, that I can do a raycast in my swipe gesture code to check if the touch hits any UI elements and if so not consider it as a swipe but I wanted to know if thats the standard way of doing it or I can somehow block events to my swipe code. I use Input.Touches in my swipe recognition which makes me believe that I will always have the touches in there even on UI buttons and might have to do some custom checking. If anyone knows of a better solution let me know. Also, feel free to use this code for your projects if anyone wants to. Thank you.

Answer 1

Answer by hulahoolgames · Aug 28, 2015 at 06:26 PM

I solved this by casting a ray from the start position of the swipe and checking if its above any UI element. If the swipe starts above a UI element its discarded. Here is the piece of code that does this

 private bool shouldDiscardSwipe(Vector2 touchPos) {
             PointerEventData touch = new    PointerEventData(EventSystem.current);
             touch.position = touchPos;
             List<RaycastResult> hits = new List<RaycastResult>();
             EventSystem.current.RaycastAll(touch, hits);
             return (hits.Count > 0); // discard swipe if an UI element is beneath
         }

Hope this helps someone.

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