Unity 获取鼠标悬停位置下的UI或3D物体对象

根据UGUI的射线检测机制获取当前鼠标下的UI：

/// <summary>
/// 获取鼠标停留处UI
/// </summary>
/// <param name="canvas"></param>
/// <returns></returns>
public GameObject GetOverUI(GameObject canvas)
{
PointerEventData pointerEventData = new PointerEventData(EventSystem.current);
pointerEventData.position = Input.mousePosition;
GraphicRaycaster gr = canvas.GetComponent<GraphicRaycaster>();
List<RaycastResult> results = new List<RaycastResult>();
gr.Raycast(pointerEventData, results);
if (results.Count != 0)
{
return results[0].gameObject;
}

return null;
}

其中，results为鼠标下UI的列表。

不仅适用于UGUI，可以在摄像机上添加PhysicsRaycaster组件，传参为摄像机，这样就可以获取3D物体。

/// <summary>
/// 获取鼠标停留处物体
/// </summary>
/// <param name="raycaster"></param>
/// <returns></returns>
public GameObject GetOverGameObject(GameObject raycaster)
{
PointerEventData pointerEventData = new PointerEventData(EventSystem.current);
pointerEventData.position = Input.mousePosition;
PhysicsRaycaster pr = raycaster.GetComponent<PhysicsRaycaster>();
List<RaycastResult> results = new List<RaycastResult>();
pr.Raycast(pointerEventData, results);
if (results.Count != 0)
{
return results[0].gameObject;
}

return null;
}