Unity 简单的拖拽UI实现(不触发Btn事件，有屏幕范围判定)

/**
 *Copyright(C) 2019 by #COMPANY#
 *All rights reserved.
 *FileName:     #SCRIPTFULLNAME#
 *Author:       #AUTHOR#
 *Version:      #VERSION#
 *UnityVersion：#UNITYVERSION#
 *Date:         #DATE#
 *Description:   
 *History:
*/
using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.UI;
public class Drag : MonoBehaviour
{
    private void Start()
    {
        transform.GetComponent<Button>().onClick.AddListener(() =>
        {
            Debug.Log("点击了");
        });
    }
    // Update is called once per frame
    void Update()
    {
        if (Input.GetMouseButtonDown(0))
        {
            Vector2 mousePos2D = Input.mousePosition;
            RaycastHit2D hit = Physics2D.Raycast(mousePos2D, Vector2.zero);
            if (hit.transform != null)
            {
                var listener = EventTriggerListener.Get(hit.transform);
                Vector3 offset = Vector3.zero;
                Button btn = hit.transform.GetComponent<Button>();
                listener.onBeginDrag += (go) =>
                {
                    if (btn!=null)
                    {
                        btn.enabled = false;
                    }
                    offset = hit.transform.position - Input.mousePosition;
                };
                listener.onDrag += (go) =>
                {
                    hit.transform.position = Input.mousePosition + offset;
                    DragRangeLimit(hit.transform);
                };
                listener.onEndDrag += (go) =>
                {
                    if (btn != null)
                    {
                        btn.enabled = true;
                    }
                };
            }
        }
    }

    /// <summary>
    /// 限制移动距离在屏幕内
    /// </summary>
    /// <param name="tra"></param>
    public void DragRangeLimit(Transform tra)
    {
        var pos = tra.GetComponent<RectTransform>();
        float x = Mathf.Clamp(pos.position.x, pos.rect.width * 0.5f, Screen.width - (pos.rect.width * 0.5f));
        float y = Mathf.Clamp(pos.position.y, pos.rect.height * 0.5f, Screen.height - (pos.rect.height * 0.5f));
        pos.position = new Vector2(x, y);
    }
}

需要一个类似于NGUI的事件监听类

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

public class EventTriggerListener : EventTrigger
{
    public delegate void VoidDelegate(GameObject go);
    public VoidDelegate onClick;
    public VoidDelegate onDown;
    public VoidDelegate onEnter;
    public VoidDelegate onExit;
    public VoidDelegate onUp;
    public VoidDelegate onSelect;
    public VoidDelegate onUpdateSelect;
    public VoidDelegate onDrag;
    public VoidDelegate onBeginDrag;
    public VoidDelegate onEndDrag;

    public static EventTriggerListener Get(GameObject go)
    {
        EventTriggerListener listener = go.GetComponent<EventTriggerListener>();
        if (listener == null)
            listener = go.AddComponent<EventTriggerListener>();
        return listener;
    }

    public static EventTriggerListener Get(Transform go)
    {
        EventTriggerListener listener = go.GetComponent<EventTriggerListener>();
        if (listener == null)
            listener = go.gameObject.AddComponent<EventTriggerListener>();
        return listener;
    }

    public override void OnPointerClick(PointerEventData eventData)
    {
        if (onClick != null) onClick(gameObject);
    }
    public override void OnPointerDown(PointerEventData eventData)
    {
        if (onDown != null) onDown(gameObject);
    }
    public override void OnPointerEnter(PointerEventData eventData)
    {
        if (onEnter != null) onEnter(gameObject);
    }
    public override void OnPointerExit(PointerEventData eventData)
    {
        if (onExit != null) onExit(gameObject);
    }
    public override void OnPointerUp(PointerEventData eventData)
    {
        if (onUp != null) onUp(gameObject);
    }
    public override void OnSelect(BaseEventData eventData)
    {
        if (onSelect != null) onSelect(gameObject);
    }
    public override void OnUpdateSelected(BaseEventData eventData)
    {
        if (onUpdateSelect != null) onUpdateSelect(gameObject);
    }

    public override void OnDrag(PointerEventData eventData)
    {
        if (onDrag != null) onDrag(gameObject);
    }

    public override void OnBeginDrag(PointerEventData eventData)
    {
        if (onBeginDrag != null) onBeginDrag(gameObject);
    }

    public override void OnEndDrag(PointerEventData eventData)
    {
        if (onEndDrag != null) onEndDrag(gameObject);
    }
}

按下btn失活 抬起激活 这样就实现了移动图标不会激活Btn事件
需要注意的是要拖拽的物体要添加2D碰撞 这个脚本只用挂一个.不用每个物体都挂 根据2D射线碰撞拖动

这样的话有个问题 就是你按下才注册按下事件 所以第一次按下事件不会触发 第二次才会 每次点击到都要重新注册
所以更改一下 在btn界面传入transform注册

/**
 *Copyright(C) 2019 by #COMPANY#
 *All rights reserved.
 *FileName:     #SCRIPTFULLNAME#
 *Author:       #AUTHOR#
 *Version:      #VERSION#
 *UnityVersion：#UNITYVERSION#
 *Date:         #DATE#
 *Description:   
 *History:
*/
using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.UI;
public class Drag : MonoBehaviour
{
    bool canTouch=true;
    private void Start()
    {
        RegisterDrag(transform);
        transform.GetComponent<Button>().onClick.AddListener(() =>
        {
            Debug.Log("点击了");        
        });
    }
    // Update is called once per frame
    void Update()
    {
       
            
        
    }

    /// <summary>
    /// 限制移动距离在屏幕内
    /// </summary>
    /// <param name="tra"></param>
    public void DragRangeLimit(Transform tra)
    {
        var pos = tra.GetComponent<RectTransform>();
        float x = Mathf.Clamp(pos.position.x, pos.rect.width * 0.5f, Screen.width - (pos.rect.width * 0.5f));
        float y = Mathf.Clamp(pos.position.y, pos.rect.height * 0.5f, Screen.height - (pos.rect.height * 0.5f));
        pos.position = new Vector2(x, y);
    }

    public void RegisterDrag(Transform tra)
    {
        if (tra.transform != null)
        {
            var listener = EventTriggerListener.Get(tra.transform);
            Vector3 offset = Vector3.zero;
            Button btn = tra.transform.GetComponent<Button>();
            listener.onBeginDrag += (go) =>
            {
                if (!canTouch)
                    return;  
offset = tra.transform.position - Input.mousePosition;
                if (btn != null)
                {
                    btn.enabled = false;
                }
              
            };
            listener.onDrag += (go) =>
            {
                if (!canTouch)
                    return;
                tra.transform.position = Input.mousePosition + offset;
                DragRangeLimit(tra.transform);
            };
            listener.onEndDrag += (go) =>
            {
                if (!canTouch)
                    return;
                if (btn != null)
                {
                    btn.enabled = true;
                }
            };
        }
    }
}

这样就可以丝滑般流畅 可以根据canTouch控制是否可以拖动

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