unity3d UGUI的down与up弹窗，松开时关闭窗口处理机制

挂载到对象即可，然后注册回调做down和up的处理

using UnityEngine;
using UnityEngine.EventSystems;
public class PushListener : MonoBehaviour,IPointerDownHandler, IPointerUpHandler
{
    public delegate void VoidDelegate(Transform obj, object param);
    public VoidDelegate DownCall = null;
    public object DownParam = null;
    public VoidDelegate UpCall = null;
    public object UpParam = null;

    public void OnPointerDown(PointerEventData data)
    {
        if (DownCall != null)
        {
            DownCall(transform, DownParam);
        }
    }

    public void OnPointerUp(PointerEventData data)
    {
        if (UpCall != null)
        {
            UpCall(transform, UpParam);
        }
    }

    public void SetDown(VoidDelegate call, object param)
    {
        DownCall = call;
        DownParam = param;
    }

    public void SetUp(VoidDelegate call, object param)
    {
        UpCall = call;
        UpParam = param;
    }
}