U3D-UGUI-虚拟摇杆

2020.02.12 重写了，代码有注释，结构更简单，也有源工程：Unity - UGUI快速制作虚拟摇杆 - 移动方向摇杆

代码：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using UnityEngine;
using UnityEngine.EventSystems;
using UnityEngine.UI;
/// 
/// author  :   jave.lin
/// date    :   2017-12-26
/// 
namespace Assets.Scripts.InputSimulater
{
    class InputSimulaterCtrl :
        MonoBehaviour,
        IPointerDownHandler,
        IPointerUpHandler,
        IDragHandler,
        IEndDragHandler
    {
        public RawImage m_pTouchBg;
        public RawImage m_pTouchTracker;
        public float m_fDeadZone = 0.2f;

        private float _m_fLimitRadius;
        private Vector3 _m_vMsDownBgPos;
        private Vector2 _m_vMsDownBgPosHelper;

        public Vector2 offset
        {
            get
            {
                return m_pTouchTracker.transform.localPosition.normalized;
            }
        }

        private void _resetAlpha( float a )
        {
            var c = m_pTouchTracker.color;
            c.a = a;
            m_pTouchTracker.color = c;
        }

        private void _resetPos()
        {
            m_pTouchTracker.transform.localPosition = m_pTouchBg.transform.localPosition;
        }

        void Start()
        {
            _m_fLimitRadius = m_pTouchBg.rectTransform.rect.width * 0.5f;
            _resetAlpha(0.2f);
        }

        void Update()
        {
            //Debug.Log( "offset:" + offset );
        }

        public void OnPointerDown(PointerEventData eventData)
        {
            _m_vMsDownBgPos = m_pTouchBg.transform.TransformPoint(0, 0, 0);
            _m_vMsDownBgPosHelper.Set(_m_vMsDownBgPos.x, _m_vMsDownBgPos.y);
            _resetAlpha(1f);
        }

        public void OnPointerUp(PointerEventData eventData)
        {
            _resetAlpha(0.2f);
        }

        public void OnDrag(PointerEventData eventData)
        {
            var pos = eventData.position - _m_vMsDownBgPosHelper;
            var mag = pos.magnitude ;
            if ((mag / _m_fLimitRadius) > m_fDeadZone)
            {
                if (mag > _m_fLimitRadius)
                {
                    pos = pos.normalized * _m_fLimitRadius;
                }
                if (!pos.Equals(m_pTouchTracker.transform.localPosition))
                {
                    m_pTouchTracker.transform.localPosition = pos;
                }
            }
            else
            {
                _resetPos();
            }
        }

        public void OnEndDrag(PointerEventData eventData)
        {
            _resetPos();
        }
    }
}

#运行效果