一：前言

获取到选中的文字：哈哈

---

二：实现

UGUI的InputField提供了selectionAnchorPosition和selectionFocusPosition，开始选择时的光标下标和当前光标下标

using UnityEngine;
using UnityEngine.EventSystems;
using UnityEngine.UI;
using System;

public class GameInputField : InputField
{
    private string m_SelectedText;//当前选中的文本
    public string SelectedText
    {
        get
        {
            return m_SelectedText;
        }
    }
    private int m_StartSelectedIndex;//起始选中的下标
    public int StartSelectedIndex
    {
        get
        {
            return m_StartSelectedIndex;
        }
    }
    private int m_EndSelectedIndex;//结束选中的下标
    public int EndSelectedIndex
    {
        get
        {
            return m_EndSelectedIndex;
        }
    }

    private void Update()
    {
        if (Input.GetMouseButtonDown(0) && EventSystem.current.currentSelectedGameObject == gameObject)
        {
            m_StartSelectedIndex = selectionAnchorPosition;
        }
        if (Input.GetMouseButtonUp(0) && EventSystem.current.currentSelectedGameObject == gameObject)
        {
            m_EndSelectedIndex = selectionFocusPosition;
            if (m_EndSelectedIndex < m_StartSelectedIndex)
            {
                int temp = m_StartSelectedIndex;
                m_StartSelectedIndex = m_EndSelectedIndex;
                m_EndSelectedIndex = temp;
            }
            m_SelectedText = text.Substring(m_StartSelectedIndex, m_EndSelectedIndex - m_StartSelectedIndex);
        }
    }
}