【100个 Unity实用技能】 | Unity实现Text BestFit文本超框时再缩小字体

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

public class UIText : Text
{
    #region 实现超框时再缩小字体，适配多语言
    /// <summary>
    /// 当前可见的文字行数
    /// </summary>
    public int VisibleLines { get; private set; }

    private void UseFitSettings()
    {
        TextGenerationSettings settings = GetGenerationSettings(rectTransform.rect.size);
        settings.resizeTextForBestFit = false;

        if (!resizeTextForBestFit)
        {
            cachedTextGenerator.PopulateWithErrors(text, settings, gameObject);
            return;
        }

        int minSize = resizeTextMinSize;
        int txtLen = text.Length;

        //从Best Fit中最大的值开始，逐次递减，每次减小后都尝试生成文本，
        //如果生成的文本可见字符数等于文本内容的长度，则找到满足需求(可以使所有文本都可见的最大字号)的字号。
        for (int i = resizeTextMaxSize; i >= minSize; --i)
        {
            settings.fontSize = i;
            cachedTextGenerator.PopulateWithErrors(text, settings, gameObject);
            if (cachedTextGenerator.characterCountVisible == txtLen) break;
        }
    }

    private readonly UIVertex[] _tmpVerts = new UIVertex[4];

    /// <summary>
    /// 重写绘制顶点方法
    /// </summary>
    /// <param name="toFill"></param>
    protected override void OnPopulateMesh(VertexHelper toFill)
    {
        if (null == font) return;

        m_DisableFontTextureRebuiltCallback = true;
        UseFitSettings();

        IList<UIVertex> verts = cachedTextGenerator.verts;
        float unitsPerPixel = 1 / pixelsPerUnit;
        int vertCount = verts.Count;

        // 没有要处理的对象时，直接return。
        if (vertCount <= 0)
        {
            toFill.Clear();
            return;
        }

        Vector2 roundingOffset = new Vector2(verts[0].position.x, verts[0].position.y) * unitsPerPixel;
        roundingOffset = PixelAdjustPoint(roundingOffset) - roundingOffset;
        toFill.Clear();

        for (int i = 0; i < vertCount; ++i)
        {
            int tempVertsIndex = i & 3;
            _tmpVerts[tempVertsIndex] = verts[i];
            _tmpVerts[tempVertsIndex].position *= unitsPerPixel;
            if (roundingOffset != Vector2.zero)
            {
                _tmpVerts[tempVertsIndex].position.x += roundingOffset.x;
                _tmpVerts[tempVertsIndex].position.y += roundingOffset.y;
            }
            if (tempVertsIndex == 3)
                toFill.AddUIVertexQuad(_tmpVerts);

        }

        m_DisableFontTextureRebuiltCallback = false;
        VisibleLines = cachedTextGenerator.lineCount;
    }
    #endregion
}