something about the "PointerEventData"

Unity Engine
1

hi everyone! i watched the live session about how to make a simple joystick on mobile,and i got a problem.
OK,firstly,this is my Canvas which contains three image ui elment
1918515--123828--upload_2015-1-13_12-38-25.png1918515--123829--upload_2015-1-13_12-39-32.png
and then i attach a script to my “movementZone” UI image to detect the direction to move,and the script just like this:

using UnityEngine;
using System.Collections;
using UnityEngine.UI;
using UnityEngine.EventSystems;

public class MySimpleJoyStick : MonoBehaviour ,IPointerUpHandler,IPointerDownHandler,IDragHandler{
    private Vector2 origin;
    private Vector2 direction;
    private int pointerID;
    private bool touched;

    void Awake(){
        direction = Vector2.zero;
        touched = false;
    }
    public void OnPointerDown(PointerEventData data){
        if(!touched){
            touched = true;
            origin = data.position;
            pointerID = data.pointerId;
        }
    }
    public void OnDrag(PointerEventData data){
        if(data.pointerId==this.pointerID){
            Vector2 currentPosition = data.position;
            Vector2 directionRaw = currentPosition - origin;
            direction = directionRaw.normalized;
        }
    }
    public void OnPointerUp(PointerEventData data){
        if(data.pointerId==pointerID){
            direction = Vector2.zero;
            touched = false;
        }
    }
    public Vector2 GetDirection(){
        return direction;
    }
}

the problem is that when i first finger touched and moved whthin the area of the movement zone ,it works fine.
however when i put another finger on my screen, it will affect my movement.
that’s stranger,becase i already use pointerid to make sure only one finger will be effectively.
thanks you guys in advanced!!:wink:

2

in the OnDrag(),i added a condition input.touchCount==1 , the problem disappeared.