unity3d 根据手指触摸的位置去放置UI

private Vector3 m_uiWroldPos;
void Update()
{
if (Input.GetMouseButton(0))
{
m_uiWroldPos=UICamera.mainCamera.ScreenToWorldPoint(
new Vector3(Input.mousePosition.x,Input.mousePosition.y,0));
if (m_spr != null && m_parentPanel != null)
{
m_spr.transform.localPosition = m_parentPanel.transform.InverseTransformPoint(m_uiWroldPos);
}
}
}