用代码写一个虚拟摇杆

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

public class Joystick : MonoBehaviour,IPointerDownHandler,IPointerUpHandler,IDragHandler{
    /// <summary>
    /// 虚拟摇杆的底图
    /// </summary>
    public Image backGroundImage;
    /// <summary>
    /// 虚拟摇杆显示手指按下/移动区域
    /// </summary>
    public Image pointerImage;
    /// <summary>
    /// 虚拟摇杆朝哪移动
    /// </summary>
    public Vector3 moveForwad;
    /// <summary>
    /// 虚拟摇杆旋转
    /// </summary>
    public Vector3 rotationForwad;
    // Use this for initialization
    void Start () {
        
    }
    
    // Update is called once per frame
    void Update () {
        
    }/// <summary>
     /// 鼠标/手指点下移动相应处理
     /// </summary>
     /// <param name="eventData"></param>
    public void pointerMove(PointerEventData eventData)
    {
        //我们的摇杆效果
        Vector2 pos;//虚拟摇杆中心位置
        if (RectTransformUtility.ScreenPointToLocalPointInRectangle
            (backGroundImage.rectTransform,//底图
             eventData.position,//鼠标或者手指在屏幕上的位置
             eventData.enterEventCamera,//ui摄像机
             out pos     )){
            //我们将POS的X/Y进行计算，计算出来相对于宽和高比例是多少
            pos.x = pos.x / backGroundImage.rectTransform.sizeDelta.x;
            pos.y = pos.y / backGroundImage.rectTransform.sizeDelta.y;
            Debug.Log("pos=" + pos);

            //将取值范围进行调整
            pos.x = pos.x * 2 - 1;//取值范围改为[-1,1]
            pos.y = pos.y * 2 - 1;
            Debug.Log("pos=" + pos*10);
            if (pos.magnitude > 1)
            {
                pos.Normalize();
            }

            //给中心图片进行位置设定
            pointerImage.rectTransform.anchoredPosition = //pos;
            new Vector2(
            pos.x * (backGroundImage.rectTransform.sizeDelta.x / 2)
            , pos.y * (backGroundImage.rectTransform.sizeDelta.y / 2));
            //移动
            moveForwad = new Vector3(pos.x, 0, pos.y);
            //旋转
            rotationForwad = new Vector3(pos.x, 0, pos.y);
        }
    }
    /// <summary>
    /// 手指或者鼠标按下事件
    /// </summary>
    /// <param name="eventData"></param>
    public void OnPointerDown(PointerEventData eventData)
    {
        Debug.Log("手指按下");
        pointerMove(eventData);
    }
    /// <summary>
    /// 手指或者鼠标抬起事件
    /// </summary>
    /// <param name="eventData"></param>
    public void OnPointerUp(PointerEventData eventData)
    {
        Debug.Log("手指抬起");
        pointerImage.rectTransform.anchoredPosition = Vector2.zero;//鼠标或者手指抬起后中心点回去
        moveForwad= Vector3.zero;
    }
    /// <summary>
    /// 手指或者鼠标拖拽事件
    /// </summary>
    /// <param name="eventData"></param>
    public void OnDrag(PointerEventData eventData)
    {
        Debug.Log("手指拖拽");
        pointerMove(eventData);
    }
}