//触发器事件, Tigger
private void OnTriggerEnter(Collider other)
private void OnTriggerStay(Collider other)
private void OnTriggerExit(Collider other)
//碰撞器事件, Collision
private void OnCollisionEnter(Collision collision)
private void OnCollisionStay(Collision collision)
private void OnCollisionExit(Collision collision)

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

public class NPC : MonoBehaviour
{   
    public enum emTriggerType
    {
        None,
        Enter,
        Exit,
    }
    private Transform m_tfPlayer;
    private emTriggerType m_emTriggerType;
    private float m_fRotateSpeed;
    private float m_fTimer;

    private Quaternion m_srcRotation;

    // Start is called before the first frame update
    void Start()
    {
        m_tfPlayer = GameObject.FindObjectOfType<Player>().transform;
        m_emTriggerType = emTriggerType.None;
        m_fRotateSpeed = 3f;
        m_fTimer = 0f;
        m_srcRotation = transform.rotation;

        SphereCollider trigger = transform.gameObject.AddComponent<SphereCollider>();
        trigger.isTrigger = true;
        trigger.radius = 10f;
    }

    // Update is called once per frame
    void Update()
    {
        if(m_emTriggerType == emTriggerType.Enter)
        {
            //玩家位置减去NPC位置，得到非单位化的向量dir，几何意义是NPC指向玩家位置的方向向量
            Vector3 dir = m_tfPlayer.transform.position - transform.position;
            Quaternion targetQ = Quaternion.LookRotation(dir, Vector3.up);
            transform.rotation = Quaternion.Lerp(transform.rotation, targetQ, Time.deltaTime * m_fRotateSpeed);

            m_fTimer += Time.deltaTime; //计时器

            if (m_fTimer >= 1f) {
                m_emTriggerType = emTriggerType.None;    //置空占位
                m_fTimer = 0;
            }
        }
        else if(m_emTriggerType == emTriggerType.Exit)
        {
            transform.rotation = Quaternion.Lerp(transform.rotation, m_srcRotation, Time.deltaTime * m_fRotateSpeed);
            m_fTimer += Time.deltaTime;

            if (m_fTimer >= 1f)
            {
                m_emTriggerType = emTriggerType.None;
                m_fTimer = 0;
            }
        }    
    }

    private void OnTriggerEnter(Collider other)
    {
        if (other.transform != m_tfPlayer) return;
        m_emTriggerType = emTriggerType.Enter;
        //Debug.Log("Trigger enter");

        //弹出对话
    }

    private void OnTriggerExit(Collider other)
    {
        if (other.transform != m_tfPlayer) return;
        m_emTriggerType = emTriggerType.Exit;
        //Debug.Log("Trigger exit");

        //关闭对话
    }
}

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.UI;   //UI的命名空间

public class Unity_Entity : MonoBehaviour
{
    private GameObject m_objModel;

    private Text m_txtCharacterName;
    private GameObject m_objHPBar;
    private Image m_imgHP;

    public Vector3 mv3Offset;
    // Start is called before the first frame update
    void Start()
    {
        GameObject uiUnit = Resources.Load<GameObject>("Prefabs/UI/Unit_Entity");    //获取UI单元
        uiUnit.SetActive(false);

        mv3Offset = new Vector3(0f, 2f, 0f);

        m_objModel = Instantiate<GameObject>(uiUnit);   //实例化对象
        m_objModel.transform.parent = GameObject.Find("UnitEntityRoot").transform;  //将对象添加到附节点

        m_txtCharacterName = m_objModel.transform.Find("Context/txtCharacterName").GetComponent<Text>();  //获取名称
        m_objHPBar = m_objModel.transform.Find("Context/HPBar").gameObject;
        m_imgHP = m_objModel.transform.Find("Context/HPBar/hp").GetComponent<Image>(); //获取血条图片资源

        m_txtCharacterName.text = this.gameObject.name;
        m_objHPBar.SetActive(!SceneManager.Instance.isMainScene);   //不在主场景时才激活血条
    }

    // Update is called once per frame
    void Update()
    {
        m_objModel.transform.position = Camera.main.WorldToScreenPoint(this.transform.position + mv3Offset);
        //从世界坐标系转换为屏幕坐标系，将血条显示在屏幕上
    }
}

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

public class SceneManager : MonoBehaviour
{
    public static SceneManager Instance;
    public bool isMainScene
    {
        get //get和set可以封装public的field(Member Variable)
        {
            UnityEngine.SceneManagement.Scene curScene = UnityEngine.SceneManagement.SceneManager.GetActiveScene();
            //由于Unity已经有ScenceManager类，因此需要额外注明命名空间
            return curScene.name == "MainScene";
        }
    }
    // Start is called before the first frame update
    void Awake() //Awake的执行顺序优先于Start()
    {
        Instance = this;
    }

    // Update is called once per frame
    void Update()
    {

    }
}