PC端

using UnityEngine;
using System.Collections;
 
public class DragRound : MonoBehaviour {
 
    public Transform obj;
    public float speed = 2;
    
    private bool _mouseDown = false;
    
    void Update () 
    {
        if (Input.GetMouseButtonDown(0))
            _mouseDown = true;
        else if (Input.GetMouseButtonUp(0))
            _mouseDown = false;

        if (_mouseDown)
        {
            float fMouseX = Input.GetAxis("Mouse X");
            float fMouseY = Input.GetAxis("Mouse Y");
            obj.Rotate(Vector3.up, -fMouseX * speed, Space.World);
            obj.Rotate(Vector3.right, fMouseY * speed, Space.World);
        }
    }
}

移动端：

using UnityEngine;
using System.Collections;
 
public class DragRoundPhone : MonoBehaviour {
 
    private Vector3 startFingerPos;
    private Vector3 nowFingerPos;
    private float xMoveDistance;
    private float yMoveDistance;
    private int backValue = 0;
    public GameObject obj;
    void Update()
    {
        if (Input.touchCount <= 0)
        {
            return;
        }
 
        if (Input.GetTouch(0).phase == TouchPhase.Began)
        {
            //Debug.Log("======开始触摸=====");  
            startFingerPos = Input.GetTouch(0).position;
        }
 
        nowFingerPos = Input.GetTouch(0).position;
 
        if ((Input.GetTouch(0).phase == TouchPhase.Stationary) || (Input.GetTouch(0).phase == TouchPhase.Ended))
        {
            startFingerPos = nowFingerPos;
            //Debug.Log("======释放触摸=====");  
            return;
        }
        //          if (Input.GetTouch(0).phase == TouchPhase.Ended) {  
        //                
        //          }  
        if (startFingerPos == nowFingerPos)
        {
            return;
        }
        xMoveDistance = Mathf.Abs(nowFingerPos.x - startFingerPos.x);
        yMoveDistance = Mathf.Abs(nowFingerPos.y - startFingerPos.y);
 
        if (xMoveDistance > yMoveDistance)
        {
            if (nowFingerPos.x - startFingerPos.x > 0)
            {
                //Debug.Log("=======沿着X轴负方向移动=====");  
                backValue = -1; //沿着X轴负方向移动  
            }
            else
            {
                //Debug.Log("=======沿着X轴正方向移动=====");  
                backValue = 1; //沿着X轴正方向移动  
            }
        }
        else
        {
            if (nowFingerPos.y - startFingerPos.y > 0)
            {
                //Debug.Log("=======沿着Y轴正方向移动=====");  
                backValue = 2; //沿着Y轴正方向移动  
            }
            else
            {
                //Debug.Log("=======沿着Y轴负方向移动=====");  
                backValue = -2; //沿着Y轴负方向移动  
            }
 
        }
        if (backValue == -1)
        {
            obj.transform.Rotate(Vector3.up * -1 * Time.deltaTime * 50, Space.World);
        }
        else if (backValue == 1)
        {
            obj.transform.Rotate(Vector3.up * Time.deltaTime * 50, Space.World);
        }
        else if (backValue == 2)
        {
            obj.transform.Rotate(Vector3.right * Time.deltaTime * 50, Space.World);
        }
        else if (backValue == -2)
        {
            obj.transform.Rotate(Vector3.right * -1 * Time.deltaTime * 50, Space.World);
        }  
 
    }  
}