Joystick

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

public class Joystick : MonoBehaviour, IDragHandler, IPointerUpHandler, IPointerDownHandler
{
    public RectTransform bgImg;
    public RectTransform joystickImg;
    public Vector3 inputVec;

    void Start ()
    {
        bgImg = GetComponent<RectTransform> ();
        joystickImg = transform.GetChild (0).GetComponent<RectTransform> ();
    }

    public virtual void OnDrag(PointerEventData ped)
    {
        Vector2 pos;

        if(RectTransformUtility.ScreenPointToLocalPointInRectangle( bgImg,
            ped.position,
            ped.pressEventCamera, out pos ))
        {
            pos.x = ( pos.x / bgImg.sizeDelta.x );
            pos.y = ( pos.y / bgImg.sizeDelta.y );

            inputVec = new Vector3( pos.x * 2 + 1, 0, pos.y * 2 - 1 );
            inputVec = ( inputVec.magnitude > 1.0f ) ? inputVec.normalized : inputVec;

            joystickImg.anchoredPosition =
                new Vector3( inputVec.x * ( bgImg.sizeDelta.x / 3 ),
                    inputVec.z * ( bgImg.sizeDelta.y / 3 ) );
        }
    }

    public virtual void OnPointerDown(PointerEventData ped)
    {
        OnDrag( ped );
    }

    public virtual void OnPointerUp(PointerEventData ped)
    {
        inputVec = Vector3.zero;
        joystickImg.anchoredPosition = Vector3.zero;
    }

    public float Horizontal ()
    {
        if (inputVec.x != 0)
            return inputVec.x;
        else
            return Input.GetAxis ("Horizontal");
    }

    public float Vertical ()
    {
        if (inputVec.z != 0)
            return inputVec.z;
        else
            return Input.GetAxis ("Vertical");
    }
}