UGUI事件系统点击响应对象的获取时机

public class TestInvoke : MonoBehaviour, IPointerDownHandler, IPointerUpHandler, IPointerClickHandler, IPointerEnterHandler, IPointerExitHandler
{
    public void OnPointerDown(PointerEventData eventData)
    {
        Debug.LogFormat("[OnPointerDown]pointerPress:{0}", eventData.pointerPress); //这个时候还是空的
        Debug.LogFormat("[OnPointerDown]selectedObject:{0}", eventData.selectedObject);
    }

    public void OnPointerUp(PointerEventData eventData)
    {
        Debug.LogFormat("[OnPointerUp]pointerPress:{0}", eventData.pointerPress);
        Debug.LogFormat("[OnPointerUp]selectedObject:{0}", eventData.selectedObject);
    }

    public void OnPointerClick(PointerEventData eventData)
    {
        Debug.LogFormat("[OnPointerClick]pointerPress:{0}", eventData.pointerPress);
        Debug.LogFormat("[OnPointerClick]selectedObject:{0}", eventData.selectedObject);
    }

    public void OnPointerEnter(PointerEventData eventData)
    {
        Debug.LogFormat("[OnPointerEnter]pointerPress:{0}", eventData.pointerPress);//这个时候还是空的
        Debug.LogFormat("[OnPointerEnter]selectedObject:{0}", eventData.selectedObject);//这个时候还是空的
    }

    public void OnPointerExit(PointerEventData eventData)
    {
        Debug.LogFormat("[OnPointerExit]pointerPress:{0}", eventData.pointerPress);//这个时候已经空了
        Debug.LogFormat("[OnPointerExit]selectedObject:{0}", eventData.selectedObject);
    }
}

通过继承几个点击相关的接口，来打日志看看，点击响应对象何时才能访问到

• pointerPress：顾名思义，发生了press才会访问到，所以在OnPointerEnter、OnPointerExit、OnPointerDown的时候是访问不到的。
• selectedObject：没有press这个限制，所以只有OnPointerEnter才访问不到。
  感觉这些接口表达的含义是，在事件发生时的前一刻。