按下移动、释放"/>
【Unity3D UGUI】事件接口(三) 按下移动、释放
【准备工作】
相关基础知识与注意事项烦请参见拙作——事件接口(零)总述
【接口介绍】
IDragHandler
该接口实现方法如下:
public void OnDrag(PointerEventData eventData)
{//当鼠标在A对象按下并拖拽时 A对象每帧响应一次此事件//注:如果不实现此接口,则后面的四个接口方法都不会触发Debug.Log("OnDrag " + name);
}
IInitializePotentialDragHandler
该接口实现方法如下:
public void OnInitializePotentialDrag(PointerEventData eventData)
{//当鼠标在A对象按下还没开始拖拽时 A对象响应此事件//注:此接口事件与IPointerDownHandler接口事件类似// 有兴趣的朋友可以测试下二者的执行顺序这里不再赘述Debug.Log("OnInitializePotentialDrag " + name);
}
IBeginDragHandler
该接口实现方法如下:
public void OnBeginDrag(PointerEventData eventData)
{//当鼠标在A对象按下并开始拖拽时 A对象响应此事件// 此事件在OnInitializePotentialDrag之后响应 OnDrag之前响应Debug.Log("OnBeginDrag " + name);
}
IEndDragHandler
该接口实现方法如下:
public void OnEndDrag(PointerEventData eventData)
{//当鼠标抬起时 A对象响应此事件Debug.Log("OnEndDrag " + name);
}
IDropHandler
该接口实现方法如下:
public void OnDrop(PointerEventData eventData)
{//A、B对象必须均实现IDropHandler接口,且A至少实现IDragHandler接口//当鼠标从A对象上开始拖拽,在B对象上抬起时 B对象响应此事件//此时name获取到的是B对象的name属性//eventData.pointerDrag表示发起拖拽的对象(GameObject)Debug.Log(eventData.pointerDrag.name + " OnDrop to " + name);
}
【应用案例】
案例说明
本案例将实现从图片组中拖出图片到目标时,释放鼠标则目标变为拖入的图片。
具体实施
(1)创建五个 Image,其中三个命名为 Image Source 并指定不同的图片作为其“Source Image”属性,其余两个命名为 Image Target,不指定图片。五张图片看心情随便摆一摆;
(2)创建 DragImage 脚本,将其指定给所有 Image Source,并添加如下代码:
/*- - - - - - - - - - - - - - - - - - - - - - - - - -*/
/* Script Editor: Eazey丶亦泽
/* Blog Adress:
/* GitHub Adress:
/*- - - - - - - - - - - - - - - - - - - - - - - - - -*//* Either none appetency, or determined to win. *//* * * * * * * * * * * * * * * * * * * * * * * * * * */
/* Script Overview: * The script target is that realize effect of drag * image.
/* * * * * * * * * * * * * * * * * * * * * * * * * * */using UnityEngine;
using UnityEngine.EventSystems;
using UnityEngine.UI;public class DragImage : MonoBehaviour,IDragHandler,IBeginDragHandler,IEndDragHandler{private Image image;private GameObject go;void OnEnable(){image = GetComponent<Image>();}public void OnBeginDrag(PointerEventData eventData){if (image.sprite == null){Debug.LogError("Current component of 'Image' have none 'Sprite'.");return;}go = new GameObject("Draging");go.transform.SetParent(eventData.pointerDrag.transform.parent);go.transform.localPosition = Vector3.zero;go.transform.localScale = Vector3.one;Image goImg = go.AddComponent<Image>();goImg.sprite = image.sprite;goImg.raycastTarget = false;}public void OnDrag(PointerEventData eventData){if (go == null)return;go.transform.position = Input.mousePosition;}public void OnEndDrag(PointerEventData eventData){Destroy(go);go = null;}
}
(3)创建 DropImage 脚本,将其指定给所有的 Image Target,并添加如下代码:
/*- - - - - - - - - - - - - - - - - - - - - - - - - -*/
/* Script Editor: Eazey丶亦泽
/* Blog Adress:
/* GitHub Adress:
/*- - - - - - - - - - - - - - - - - - - - - - - - - -*//* Either none appetency, or determined to win. *//* * * * * * * * * * * * * * * * * * * * * * * * * * */
/* Script Overview: * The script target is change the image after it had * dropped.
/* * * * * * * * * * * * * * * * * * * * * * * * * * */using UnityEngine;
using UnityEngine.EventSystems;
using UnityEngine.UI;public class DropImage : MonoBehaviour,IDropHandler {private Image image;void OnEnable(){image = GetComponent<Image>();if (image == null)image = gameObject.AddComponent<Image>();}public void OnDrop(PointerEventData eventData){Sprite s = GetSprite(eventData);if (s != null)image.sprite = s;}private Sprite GetSprite(PointerEventData eventData){GameObject goSource = eventData.pointerDrag;if (goSource == null)return null;Image imgSource = eventData.pointerDrag.GetComponent<Image>();if (imgSource == null)return null;DragImage DragSource = imgSource.GetComponent<DragImage>();if (DragSource == null)return null;return imgSource.sprite;}
}
(4)最终效果如下图所示:
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【Unity3D UGUI】事件接口(三) 按下移动、释放
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