Unity/Csharp/オブジェクトをドラッグ

unity2020の場合

using UnityEngine;
using UnityEngine.EventSystems;

public class BlockScript : MonoBehaviour, IDragHandler, IDropHandler
{
    public void OnDrag(PointerEventData eventData)
    {
        Vector3 objectPointInScreen = Camera.main.WorldToScreenPoint(eventData.position);
        Vector3 mousePointInScreen = new Vector3(Input.mousePosition.x,
            Input.mousePosition.y,
            objectPointInScreen.z);
        Vector3 mousePointInWorld = Camera.main.ScreenToWorldPoint(mousePointInScreen);
        mousePointInWorld.z = this.transform.position.z;
        this.transform.position = mousePointInWorld;
    }
    public void OnDrop(PointerEventData eventData)
    {
        //Destroy(gameObject);
    }
}

上記は、以下の項目と違って、Colliderは不要。

unity2019?

unity2020だと以下は動作しなかったので・・

画像オブジェクトにColliderをつけ以下コードをアタッチ(Add Component)するとドラッグでオブジェクトが動かせるようになる

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
public class BlockScript : MonoBehaviour {
	void Start () {
	}
	void Update () {
	}
	void OnMouseDrag()
	{
		Vector3 objectPointInScreen = Camera.main.WorldToScreenPoint(this.transform.position);
		Vector3 mousePointInScreen = new Vector3(Input.mousePosition.x,
			Input.mousePosition.y,
			objectPointInScreen.z);
		Vector3 mousePointInWorld = Camera.main.ScreenToWorldPoint(mousePointInScreen);
		mousePointInWorld.z = this.transform.position.z;
		this.transform.position = mousePointInWorld;
	}
}

参考

http://neareal.com/1230/

別の方法その１

Rididbody2DとCollider2D追加

using UnityEngine;
using UnityEngine.EventSystems;

public class DragImage : MonoBehaviour, IBeginDragHandler, IDragHandler
{
    private Vector2 prevPos;

    public void OnBeginDrag(PointerEventData eventData)
    {
        prevPos = transform.position;
    }

    public void OnDrag(PointerEventData eventData)
    {
        transform.position = eventData.position;
    }

    public void OnEndDrag(PointerEventData eventData)
    {
        transform.position = eventData.position - prevPos;
    }
}

参考：http://matorierunormal.sblo.jp/article/187233424.html