Unity基于NGUI的简单并可直接使用的虚拟摇杆实现（一）

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class JoyStickControl : MonoBehaviour
{
    public enum ShowType{Static,Dynamic}; //显示模式
    public ShowType showType= ShowType.Static;
    public float radiusOffset = 0.0F; //半径偏移值、用于图片问题造成的偏差进行微调
    public GameObject area = null;   //Dynamic模式下的显示区域
    private float radius;       //底盘半径
    private float ratio=1.0F;   //缩放值
    private bool isPress = false;   //是否是按下状态
    private bool isFirstPress = false;  //是否第一次按下
    private Vector2 offset;  //手指相对于按钮的偏移值

    private void Awake()
    {
        //获取底盘半径
        UI2DSprite parentSpirite = transform.parent.GetComponent<UI2DSprite>();
        float parentWidth = parentSpirite.width;
        radius = parentWidth / 2.0F+ radiusOffset;

        //获取缩放值
        UIRoot root = GameObject.FindObjectOfType<UIRoot>();
        if (root != null)
        {
            // 实际尺寸和设计尺寸比例
            ratio = (float)root.activeHeight / Screen.height;
        }

        //如果是Dynamic模式、一开始隐藏摇杆、并将Area设置到近乎透明
        if (showType == ShowType.Dynamic)
        {
            transform.parent.gameObject.SetActive(false);
            if (area != null)
            {
                UITexture areaTexture = area.GetComponent<UITexture>();
                areaTexture.color = new Color(1.0F, 1.0F, 1.0F, 1.0F/255.0F);
            }
        }
        else
        {
            if (area != null)
            {
                area.SetActive(false);
            }
        }
    }

    // Update is called once per frame
    private void Update()
    {
        // 触摸按下
        if (isPress)
        {
            //最后一次触摸位置、基于屏幕坐标
            Vector2 touchpos = UICamera.lastEventPosition;
            //获取摇杆按钮的屏幕坐标
            Vector2 childCenterPos = UICamera.currentCamera.WorldToScreenPoint(transform.position);
            //第一次触摸的时候获取手指相对于按钮的偏移值
            if (!isFirstPress)
            {
                offset = touchpos - childCenterPos;
                isFirstPress = true;
            }
            
            //获取摇杆底盘的屏幕坐标
            Vector2 centerPos = UICamera.currentCamera.WorldToScreenPoint(transform.parent.position);

            //获取touchpos - offset和centerPos之间的距离值
            //凡是用到touchpos - offset的地方绝对不能用childCenterPos替代、可以考虑下为什么
            float distance = Vector2.Distance(touchpos - offset, centerPos);

            //如果距离小于半径，则将按钮位置移动到touchpos - offset位置
            //distance算到的相对距离，需要乘以缩放值
            if (distance * ratio < radius)// 距离在父精灵背景中圆内，radius为其半径
            {
                Vector3 worldTouchPos = UICamera.currentCamera.ScreenToWorldPoint(touchpos - offset);
                transform.position = worldTouchPos;
            }
            //距离超过半径、则把按钮的位置设置在底盘的圆上
            else
            {
                transform.localPosition = (touchpos - offset - centerPos).normalized * radius;
                childCenterPos = UICamera.currentCamera.WorldToScreenPoint(transform.position);
            }

        }
        // 触摸抬起、那么把按钮位置恢复到原点、 将isFirstPress置否，如果是Dynamic模式、还要隐藏摇杆
        else
        {
            if (showType == ShowType.Dynamic)
            {
                transform.parent.gameObject.SetActive(false);
            }
            transform.localPosition = Vector2.zero;
            isFirstPress = false;
        }
    }

    // 触摸按下、isPress为true、抬起为false
    public void OnPress(bool isPress)
    { 
        this.isPress = isPress;
    }

    //用于Dynamic模式press事件的响应
    public void startTouch()
    {
        if (showType == ShowType.Dynamic)
        {
            transform.parent.gameObject.SetActive(true);
            Vector2 startTouchPos = UICamera.lastEventPosition;
            Vector2 startTouchWorldPos = UICamera.currentCamera.ScreenToWorldPoint(startTouchPos);
            transform.parent.position = startTouchWorldPos;
            this.isPress = true;
        }
    }

    //用于Dynamic模式release事件的响应
    public void endTouch()
    {
        if (showType == ShowType.Dynamic)
        {
            transform.parent.gameObject.SetActive(false);
        }
        transform.localPosition = Vector2.zero;
        isFirstPress = false;
    }
}