unity ui中使用onmouseover

unity ui中鼠标移进或者移出的触发方式与2d、3d的不同，2d、3d物体使用的是onmouseover，ui使用的是OnPointerEnter。需要实现以下两个接口。

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" );
    }
}

　　原文出自unity官方论坛，详情可以查看https://forum.unity.com/threads/problem-with-onmousedown-onmouseover-in-ui.326096/