https://www.cnblogs.com/jiangshuai52511/p/6649843.html

Vector3的拖拽

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


public class ControlTheMouseMove : MonoBehaviour {

    private Vector3 _vec3TargetScreenSpace;// 目标物体的屏幕空间坐标  
    private Vector3 _vec3TargetWorldSpace;// 目标物体的世界空间坐标  
    private Transform _trans;// 目标物体的空间变换组件  
    private Vector3 _vec3MouseScreenSpace;// 鼠标的屏幕空间坐标  
    private Vector3 _vec3Offset;// 偏移 
    GameObject obj;
    float speed = 5f;
    bool isClick = false;
    private Transform m_Transform;
    // Use this for initialization


    void Awake() {
        _trans = transform;
    }

    void Start () {
        m_Transform = gameObject.GetComponent<Transform>();
        obj = GameObject.Find("Cube");
    } 
    
    // Update is called once per frame
    void Update () {

       MoveControl();
        if(Input.GetKey(KeyCode.Mouse1))
        {
            isClick = true;
        }
        if(isClick)
        {
            obj.transform.Translate(Vector3.forward * speed * Time.deltaTime);
        }
    }

    void MoveControl()
    {
        m_Transform.Rotate(Vector3.up, Input.GetAxis("Mouse X"));
        m_Transform.Rotate(Vector3.left, Input.GetAxis("Mouse Y"));
      m_Transform.Rotate(Vector3.forward, Input.GetAxis("Mouse forward"));
      m_Transform.Rotate(Vector3.back, Input.GetAxis("Mouse back"));
       
    }
    IEnumerator OnMouseDown()

    {

        // 把目标物体的世界空间坐标转换到它自身的屏幕空间坐标   

        _vec3TargetScreenSpace = Camera.main.WorldToScreenPoint(_trans.position);

        // 存储鼠标的屏幕空间坐标（Z值使用目标物体的屏幕空间坐标）   

        _vec3MouseScreenSpace = new Vector3(Input.mousePosition.x, Input.mousePosition.y, _vec3TargetScreenSpace.z);

        // 计算目标物体与鼠标物体在世界空间中的偏移量   

        _vec3Offset = _trans.position - Camera.main.ScreenToWorldPoint(_vec3MouseScreenSpace);

        // 鼠标左键按下   

        while (Input.GetMouseButton(0))
        {

            // 存储鼠标的屏幕空间坐标（Z值使用目标物体的屏幕空间坐标）  

            _vec3MouseScreenSpace = new Vector3(Input.mousePosition.x, Input.mousePosition.y, _vec3TargetScreenSpace.z);

            // 把鼠标的屏幕空间坐标转换到世界空间坐标（Z值使用目标物体的屏幕空间坐标），加上偏移量，以此作为目标物体的世界空间坐标  

            _vec3TargetWorldSpace = Camera.main.ScreenToWorldPoint(_vec3MouseScreenSpace) + _vec3Offset;

            // 更新目标物体的世界空间坐标   

            _trans.position = _vec3TargetWorldSpace;

            // 等待固定更新   

            yield return new WaitForFixedUpdate();
        }
    }


}

Vector2的拖拽

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

public class ImageMove : MonoBehaviour, IBeginDragHandler, IDragHandler {

    //鼠标第一次点击的位置    
    Vector2 firstMousePos = Vector3.zero;

    //鼠标拖拽的位置    
    Vector2 secondMousePos = Vector3.zero;
    //偏移量    
    Vector3 offsetPos = Vector3.zero;

    public void OnBeginDrag(PointerEventData eventData)    {

        firstMousePos = Input.mousePosition;
        print(123);
    }
    public void OnDrag(PointerEventData eventData)    {
        secondMousePos = Input.mousePosition;
        //需要移动的 向量       
        offsetPos = secondMousePos - firstMousePos;
        float x = transform.localPosition.x;
        float y = transform.localPosition.y;
        //向量偏移        
        x = x + offsetPos.x; y = y + offsetPos.y;
        //x = Mathf.Clamp(x, 380, 1550);        
        //y = Mathf.Clamp(y, 210, 850);        
        transform.localPosition = new Vector3(x, y, transform.localPosition.z);
        firstMousePos = secondMousePos;

        print(firstMousePos);
        print(secondMousePos);
    }
}