示例：按回车键发送输入消息

using UnityEngine;
using TMPro;
/// <summary>
/// 按键盘Enter键发送输入消息
/// </summary>
public class KeyEnterSend : MonoBehaviour
{
    [SerializeField]
    private TMP_InputField m_InputField;

    private void Awake()
    {
        m_InputField.onEndEdit.AddListener(OnInputFieldEndEdit);
    }

    // 完成编辑时触发，也可理解为失去焦点时触发。
    private void OnInputFieldEndEdit(string value)
    {
        //回车(KeyCode.Return)
        //小键盘回车(KeyCode.KeypadEnter)
        if (Input.GetKeyDown(KeyCode.Return) || Input.GetKeyDown(KeyCode.KeypadEnter))
        {
            Debug.LogFormat("发送消息: {0}", value);
        }
    }
}