unity ui中使用onmouseover

public class TrackMouse: MonoBehaviour, IPointerEnterHandler, IPointerExitHandler
{
    // Called when the pointer enters our GUI component.
    // Start tracking the mouse
    public void OnPointerEnter( PointerEventData eventData )
    {
        StartCoroutine( "TrackPointer" );          
    }
 
    // Called when the pointer exits our GUI component.
    // Stop tracking the mouse
    public void OnPointerExit( PointerEventData eventData )
    {
        StopCoroutine( "TrackPointer" );
    }
 
    IEnumerator TrackPointer()
    {
        var ray = GetComponentInParent<GraphicRaycaster>();
        var input = FindObjectOfType<StandaloneInputModule>();
 
        if( ray != null && input != null )
        {
            while( Application.isPlaying )
            {                  
                Vector2 localPos; // Mouse position  
                RectTransformUtility.ScreenPointToLocalPointInRectangle( transform as RectTransform, Input.mousePosition, ray.eventCamera, out localPos );
                     
                // local pos is the mouse position.
                     
                yield return 0;
            }      
        }
        else
            UnityEngine.Debug.LogWarning( "Could not find GraphicRaycaster and/or StandaloneInputModule" );      
    }
}