Unity学习之FSM有限状态机

前言：一个游戏里的一个人物会存在多种状态，那么就需要有一个专门管理这些状态的类。不然会显得杂乱无章，不易于后面状态的增加或者减少。
思路：既然要方便管理，那么首先肯定得有个系统类（专门用来存放所有的状态、状态的增删等功能）；然后就是需要把所有的状态都单独写一个类（已达到修改某个状态的时候，其他状态不会受到影响）。

状态管理类：

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

public class FSMSystem
{
    private Dictionary<StateID, FSMState> states = new Dictionary<StateID, FSMState>();

    private StateID currentStateID;
    private FSMState currentFSMState;

    public void Update(GameObject npc)
    {
        currentFSMState.Act(npc);
        currentFSMState.Reason(npc);
    }

    /// <summary>
    /// 添加状态
    /// </summary>
    /// <param name="fSMState"></param>
    public void AddState(FSMState fSMState)
    {
        if (fSMState == null) return;

        //if (currentFSMState == null)
        //{
            currentStateID = fSMState.ID;
            currentFSMState = fSMState;
        //}
        if (states.ContainsKey(currentStateID)) return;
        states.Add(currentStateID, currentFSMState);
    }
    /// <summary>
    /// 删除状态
    /// </summary>
    /// <param name="stateID"></param>
    public void DeleteState(StateID stateID)
    {
        if (stateID == StateID.Null) return;
        if (!states.ContainsKey(stateID)) return;

        states.Remove(stateID);
    }

    /// <summary>
    /// 执行状态条件转换
    /// </summary>
    /// <param name="transition"></param>
    public void PerformTransition(Transition transition)
    {
        if (transition == Transition.NullTransition) return;

        StateID stateID = currentFSMState.GetStateID(transition);
        if (stateID == StateID.Null) return;
        if (!states.ContainsKey(stateID)) return;

        FSMState fSMState = states[stateID];
        currentFSMState.StateExit();
        currentFSMState = fSMState;
        currentStateID = fSMState.ID;
        currentFSMState.StateEnter();
    }
}

状态基类：

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

public enum Transition
{
    NullTransition,
    SeePlayer,//发现玩家
    LostPlayer,//玩家脱离视野范围
    AttackPlayer,//攻击玩家
}
public enum StateID
{
    Null,
    Chase,//追逐
    Patrol,//巡逻
    Attack,//攻击
}
public abstract class FSMState
{
    protected Transition transition;

    protected StateID stateID;
    protected FSMSystem fSM;
    public StateID ID
    {
        get { return stateID; }
    }

    protected Dictionary<Transition, StateID> dic = new Dictionary<Transition, StateID>();

    public FSMState(FSMSystem fSM)
    {
        this.fSM = fSM;
    }

    /// <summary>
    /// 增加状态
    /// </summary>
    /// <param name="transition"></param>
    /// <param name="stateID"></param>
    public void AddTransition(Transition transition, StateID stateID)
    {
        if (transition == Transition.NullTransition) return;
        if (stateID == StateID.Null) return;
        if (dic.ContainsKey(transition)) return;

        dic.Add(transition, stateID);
    }
    /// <summary>
    /// 删除状态
    /// </summary>
    /// <param name="transition"></param>
    public void DeleteTransition(Transition transition)
    {
        if (transition == Transition.NullTransition) return;
        if (!dic.ContainsKey(transition)) return;

        dic.Remove(transition);
    }
    /// <summary>
    /// 获取状态
    /// </summary>
    /// <param name="transition"></param>
    /// <returns></returns>
    public StateID GetStateID(Transition transition)
    {
        if (transition == Transition.NullTransition) return StateID.Null;
        if (!dic.ContainsKey(transition)) return StateID.Null;
        return dic[transition];
    }

    /// <summary>
    /// 进入状态
    /// </summary>
    public virtual void StateEnter() { }
    /// <summary>
    /// 退出状态
    /// </summary>
    public virtual void StateExit() { }

    /// <summary>
    /// 状态持续中，，，
    /// </summary>
    /// <param name="npc"></param>
    public abstract void Act(GameObject npc);
    /// <summary>
    /// 状态退出前，，，
    /// </summary>
    /// <param name="npc"></param>
    public abstract void Reason(GameObject npc);
}

巡逻状态：

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

/// <summary>
/// 巡逻状态
/// </summary>
public class PatrolState : FSMState
{
    /// <summary>
    /// 巡逻路径点集合
    /// </summary>
    private Transform[] paths;
    /// <summary>
    /// 当前巡逻路径点索引
    /// </summary>
    private int index = 0;
    /// <summary>
    /// 移动速度
    /// </summary>
    private float moveSpeed = 0.5f;
    /// <summary>
    /// 玩家
    /// </summary>
    private Transform player;
    public PatrolState(FSMSystem fSM, Transform player) : base(fSM)
    {
        this.player = player;
        paths = GameObject.Find("Path").GetComponentsInChildren<Transform>();
        stateID = StateID.Patrol;
    }

    public override void Act(GameObject npc)
    {
        npc.transform.LookAt(paths[index].position);
        npc.transform.Translate(Vector3.forward * Time.deltaTime * moveSpeed);
        if (Vector3.Distance(npc.transform.position, paths[index].position) < 1)
        {
            index++;
            index %= paths.Length;
        }
    }

    public override void Reason(GameObject npc)
    {
        npc.GetComponent<Animator>().SetFloat("Speed", moveSpeed );
        if (Vector3.Distance(player.position, npc.transform.position) < 10)
        {
            fSM.PerformTransition(Transition.SeePlayer);
        }
    }
}

追逐状态：

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

/// <summary>
/// 追逐状态
/// </summary>
public class ChaseState : FSMState
{
    /// <summary>
    /// 移动速度
    /// </summary>
    private float moveSpeed = 2f;
    /// <summary>
    /// 玩家
    /// </summary>
    private Transform player;
    public ChaseState(FSMSystem fSM, Transform player) : base(fSM)
    {
        stateID = StateID.Chase;
        this. player = player;
    }

    public override void Act(GameObject npc)
    {
        npc.transform.LookAt(player.position);
        npc.transform.Translate(Vector3.forward * Time.deltaTime * moveSpeed);
    }

    public override void Reason(GameObject npc)
    {
        npc.GetComponent<Animator>().SetFloat("Speed", moveSpeed / 2);
        if (Vector3.Distance(player.position, npc.transform.position) >= 10)
        {
            fSM.PerformTransition(Transition.LostPlayer);
        }
        else if (Vector3.Distance(player.position, npc.transform.position) <= 1f )
        {
            fSM.PerformTransition(Transition.AttackPlayer);
        }
    }
}

攻击状态：

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

/// <summary>
/// 攻击状态
/// </summary>
public class AttackState : FSMState
{
    /// <summary>
    /// 玩家
    /// </summary>
    private Transform player;
    public AttackState(FSMSystem fSM, Transform player) : base(fSM)
    {
        stateID = StateID.Attack;
        this.player = player;
    }
    public override void Act(GameObject npc)
    {

    }

    public override void Reason(GameObject npc)
    {
        if (Vector3.Distance(player.position, npc.transform.position) > 1f)
        {
            if (Vector3.Distance(player.position, npc.transform.position) >= 10)
            {
                fSM.PerformTransition(Transition.LostPlayer);
            }
            else if (Vector3.Distance(player.position, npc.transform.position) < 10)
            {
                fSM.PerformTransition(Transition.SeePlayer);
            }
            return;
        }
        npc.GetComponent<Animator>().SetTrigger("Attack01");
    }
}

状态持有者实现类：

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

public class Enemy : MonoBehaviour
{
    private FSMSystem fSM;
    private Transform player;
    private void Start()
    {
        fSM = new FSMSystem();
        FSMState patrolState = new PatrolState(fSM, player);
        patrolState.AddTransition(Transition.SeePlayer, StateID.Chase);
        patrolState.AddTransition(Transition.AttackPlayer, StateID.Attack);
        //patrolState.AddTransition(Transition.LostPlayer, StateID.Patrol);

        FSMState chaseState = new ChaseState(fSM, player);
        chaseState.AddTransition(Transition.LostPlayer, StateID.Patrol);
        chaseState.AddTransition(Transition.AttackPlayer, StateID.Attack);
        //chaseState.AddTransition(Transition.SeePlayer, StateID.Chase);

        FSMState attackState = new AttackState(fSM, player);
        attackState.AddTransition(Transition.SeePlayer, StateID.Chase);
        attackState.AddTransition(Transition.LostPlayer, StateID.Patrol);
        //attackState.AddTransition(Transition.AttackPlayer, StateID.Attack);

        fSM.AddState(patrolState);
        fSM.AddState(chaseState);
        fSM.AddState(attackState);
    }

    private void Update()
    {
        fSM.Update(gameObject);
    }
}

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