unity的Text下划线效果

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.EventSystems;
using UnityEngine.UI;


class UnderlineProperty
{
    public Color _color;
    public Vector3 _position;
    public float _width;
    public float _height;
    public Vector2 _privot;
}

/// 

/// 添加下划线
/// 
public class LinkText : MonoBehaviour, IPointerDownHandler, IPointerUpHandler
{

    private Text _text;
    private int _curCharacterCount = 0;
    private List _lines = new List();
    private System.Action _clickEvent = null; //下划线点击事件
    private bool _isInitUnderline = false;

    private int text_length;

    void Start()
    {
        _text = transform.GetComponent();

        text_length = CalculateLengthOfText(_text.text, _text);

    }

    void Update()
    {
        //做初始化
        if (_text.cachedTextGenerator.lineCount > 0 && !_isInitUnderline)
        {
            _isInitUnderline = true;
            _curCharacterCount = _text.cachedTextGenerator.characterCount;
            List list = GetUnderlinePropertys();
            CreateUnderLines(list);
            int avg = text_length / _lines.Count;

            for (int i = 0; i < _lines.Count; i++)
            {
                _lines[i].rectTransform.sizeDelta = new Vector2(avg, _lines[i].rectTransform.sizeDelta.y);
            }

        }

        //刷新
        if (_isInitUnderline && _curCharacterCount != _text.cachedTextGenerator.characterCount)
        {
            _curCharacterCount = _text.cachedTextGenerator.characterCount;
            List list = GetUnderlinePropertys();
            CreateUnderLines(list);
            int avg = text_length / _lines.Count;

            for (int i = 0; i < _lines.Count; i++)
            {
                _lines[i].rectTransform.sizeDelta = new Vector2(avg, _lines[i].rectTransform.sizeDelta.y);
            }
        }
    }

    List GetUnderlinePropertys()
    {
        List list = new List();
        for (int i = 0; i < _text.cachedTextGenerator.lineCount; i++)
        {
            var curPos = _text.cachedTextGenerator.characters[_text.cachedTextGenerator.lines[i].startCharIdx].cursorPos;
            UnderlineProperty property = new UnderlineProperty
            {
                _color = _text.color,
                _height = _text.fontSize / 10 == 0 ? 1 : _text.fontSize / 10,
                _width = GetWidth(_text.cachedTextGenerator.lines[i].startCharIdx, _text.cachedTextGenerator.characters),
                _position = new Vector3(curPos.x, curPos.y - _text.cachedTextGenerator.lines[i].height, 0),
                _privot = GetTextAnchorPivot(_text.alignment)
            };

            list.Add(property);
        }

        return list;
    }

    float GetWidth(int idx, IList info)
    {
        float width = 0;
        float start = info[idx].cursorPos.x;
        for (int i = idx; i < info.Count - 1; i++)
        {
            if (info[i].cursorPos.x > info[i + 1].cursorPos.x)
            {
                width = info[i].cursorPos.x - start;
                break;
            }

            if (info.Count - 1 == i + 1)
                width = info[i + 1].cursorPos.x - start;
        }
        return width;
    }

    Vector2 GetTextAnchorPivot(TextAnchor anchor)
    {
        switch (anchor)
        {
            case TextAnchor.LowerLeft: return new Vector2(0, 0);
            case TextAnchor.LowerCenter: return new Vector2(0.5f, 0);
            case TextAnchor.LowerRight: return new Vector2(1, 0);
            case TextAnchor.MiddleLeft: return new Vector2(0, 0.5f);
            case TextAnchor.MiddleCenter: return new Vector2(0.5f, 0.5f);
            case TextAnchor.MiddleRight: return new Vector2(1, 0.5f);
            case TextAnchor.UpperLeft: return new Vector2(0, 1);
            case TextAnchor.UpperCenter: return new Vector2(0.5f, 1);
            case TextAnchor.UpperRight: return new Vector2(1, 1);
            default: return Vector2.zero;
        }
    }

    void CreateUnderLines(List list)
    {
        for (int i = 0; i < transform.childCount; i++)
            Destroy(transform.GetChild(i).gameObject);
        _lines.Clear();

        for (int i = 0; i < list.Count; i++)
        {
            //初始化
            GameObject obj = new GameObject();
            obj.transform.SetParent(transform, false);
            obj.name = "underline" + i;
            _lines.Add(obj.AddComponent());
            _lines[i].rectTransform.pivot = list[i]._privot;

            //颜色和大小
            var tex = new Texture2D((int)list[i]._width, (int)list[i]._height, TextureFormat.ARGB32, false);
            Color[] colors = tex.GetPixels();
            for (int j = 0; j < colors.Length; j++)
                colors[j] = list[i]._color;
            tex.SetPixels(colors);
            tex.Apply();
            _lines[i].sprite = Sprite.Create(tex, new Rect(0, 0, tex.width, tex.height), Vector2.zero);
            _lines[i].SetNativeSize();
            _lines[i].rectTransform.sizeDelta = new Vector2(_lines[i].rectTransform.sizeDelta.x, _lines[i].rectTransform.sizeDelta.y);

            //坐标
            float x = list[i]._position.x;
            if (_text.alignment == TextAnchor.MiddleCenter || _text.alignment == TextAnchor.UpperCenter || _text.alignment == TextAnchor.LowerCenter)
                x = 0;
            if (_text.alignment == TextAnchor.MiddleRight || _text.alignment == TextAnchor.UpperRight || _text.alignment == TextAnchor.LowerRight)
                x += list[i]._width;
            _lines[i].rectTransform.anchoredPosition = new Vector2(x, list[i]._position.y);
        }
    }

    /*实现下划线同步点击效果*/
    public void OnPointerDown(PointerEventData eventData)
    {
        for (int i = 0; i < _lines.Count; i++)
        {
            Color[] colors = _lines[i].sprite.texture.GetPixels();
            for (int j = 0; j < colors.Length; j++)
                colors[j] = new Color(colors[j].r, colors[j].g, colors[j].b, colors[j].a * 0.70f);
            _lines[i].sprite.texture.SetPixels(colors);
            _lines[i].sprite.texture.Apply();
        }
    }

    public void OnPointerUp(PointerEventData eventData)
    {
        for (int i = 0; i < _lines.Count; i++)
        {
            Color[] colors = _lines[i].sprite.texture.GetPixels();
            for (int j = 0; j < colors.Length; j++)
                colors[j] = new Color(colors[j].r, colors[j].g, colors[j].b, colors[j].a / 0.70f);
            _lines[i].sprite.texture.SetPixels(colors);
            _lines[i].sprite.texture.Apply();
        }
    }
    int CalculateLengthOfText(string message, Text tex)
    {
        int totalLength = 0;
        Font myFont = tex.font;  //chatText is my Text component
        myFont.RequestCharactersInTexture(message, tex.fontSize, tex.fontStyle);
        CharacterInfo characterInfo = new CharacterInfo();

        char[] arr = message.ToCharArray();

        foreach (char c in arr)
        {
            myFont.GetCharacterInfo(c, out characterInfo, tex.fontSize);

            totalLength += characterInfo.advance;
        }

        return totalLength;
    }

}