[Unity][UGUI]获得鼠标对应屏幕的坐标，图片跟随鼠标移动

Input.mousePosition

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

public class Test_Mouse : MonoBehaviour {

    public GameObject go;

	// Use this for initialization
	void Start () {
		
	}
	
	// Update is called once per frame
	void Update () {
        Debug.Log("    "+Input.mousePosition);
        //go.GetComponent().sizeDelta = new Vector2(Input.mousePosition.x, Input.mousePosition.y);
        //go.GetComponent().localPosition = new Vector3(Input.mousePosition.x, Input.mousePosition.y,0);
        //Camera.main.WorldToScreenPoint(Input.mousePosition);
        go.GetComponent().position = new Vector3(Input.mousePosition.x, Input.mousePosition.y, 0);
    }
}

因为

Input.mousePosition

计算的坐标，是以左下角为 原点。

所以跟随的Image图片的锚点，要设置为左下角。

并且Rect Transform的Pos X ,Pos Y,Pos Z为0，0，0

go.GetComponent().position = new Vector3(Input.mousePosition.x, Input.mousePosition.y, 0);

注意这里 的Image的 位置不能是 localPosition，会产生 偏差。

正确的是position。

你会发现，是Image图片的 中点，跟随 鼠标进行移动。

----------------------------------------

go.GetComponent().sizeDelta【参考文章1，2】

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

public class Test_Mouse : MonoBehaviour {

    public GameObject go;

	// Use this for initialization
	void Start () {
		
	}
	
	// Update is called once per frame
	void Update () {
        Debug.Log("    "+Input.mousePosition);
        //go.GetComponent().sizeDelta = new Vector2(Input.mousePosition.x, Input.mousePosition.y);
        //go.GetComponent().localPosition = new Vector3(Input.mousePosition.x, Input.mousePosition.y,0);
        //Camera.main.WorldToScreenPoint(Input.mousePosition);
        go.GetComponent().position = new Vector3(Input.mousePosition.x- (go.GetComponent().sizeDelta.x/2),
            Input.mousePosition.y - (go.GetComponent().sizeDelta.y / 2)
            , 0);
    }
}

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

public class Test_Mouse : MonoBehaviour {

    public GameObject go;

	// Use this for initialization
	void Start () {
		
	}
	
	// Update is called once per frame
	void Update () {
        Debug.Log("    "+Input.mousePosition);
        //go.GetComponent().sizeDelta = new Vector2(Input.mousePosition.x, Input.mousePosition.y);
        //go.GetComponent().localPosition = new Vector3(Input.mousePosition.x, Input.mousePosition.y,0);
        //Camera.main.WorldToScreenPoint(Input.mousePosition);
        go.GetComponent().position = new Vector3(Input.mousePosition.x + (go.GetComponent().sizeDelta.x/2),
            Input.mousePosition.y + (go.GetComponent().sizeDelta.y / 2)
            , 0);
    }
}

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

public class Test_Mouse : MonoBehaviour {

    public GameObject go;

	// Use this for initialization
	void Start () {
		
	}
	
	// Update is called once per frame
	void Update () {
        Debug.Log("    "+Input.mousePosition);
        //go.GetComponent().sizeDelta = new Vector2(Input.mousePosition.x, Input.mousePosition.y);
        //go.GetComponent().localPosition = new Vector3(Input.mousePosition.x, Input.mousePosition.y,0);
        //Camera.main.WorldToScreenPoint(Input.mousePosition);
        go.GetComponent().position = new Vector3(Input.mousePosition.x + (go.GetComponent().sizeDelta.x/2),
            Input.mousePosition.y - (go.GetComponent().sizeDelta.y / 2)
            , 0);
    }
}

----------------------------------------

参考文章：

1.UGUI之RectTransform知识点 图解
http://www.manew.com/thread-41633-1-1.html
(出处: -【游戏蛮牛】-ar增强现实,虚拟现实,unity3d,unity3d教程下载首选u3d,unity3d官网)

2.

ugui在运行时改变RectTransform的大小

3.

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