20250523-简易的状态机代码模板及分析

20250523-简易的状态机代码模板及分析

前情提要，以下是个人对状态机的部分理解：

（1）状态机示例主要包括Player、PlayerStateMachine、PlayerState三部分；

（2）Player既作为小数据库（有点像单例模式的对象池），存储Player相关属性、创建全局唯一的状态对象和状态机对象；又通过继承MonoBehavior类，执行整个生命周期（Awake、Start、Update等），在各个生命周期函数中调用状态机对象；Player对象本身代表Unity悬挂脚本的组件；

（3）PlayerStateMachine为状态机对象，主要维护一个属性，即当前对象正处于哪个状态；主要有两个动作：一是状态初始化，一般只会有一次；二是当前状态的切换；

（4）PlayerState表示对象的一种状态（可继续细分），一般维护状态的某些信息，如状态名称等；还要获得Player对象和PlayerStateMachine对象用于在执行某些动作时方便调用，例如当Player对象的某个属性满足条件时，进行切换当前状态的操作。主要的动作有三个方面：一是进入状态是干什么；二是处于当前状态时需要一直重复干什么；三是退出当前状态是需要干什么（例如重置某些属性的数值等）；


以下是代码：

PlayerState.cs

using System.Collections;
using System.Collections.Generic;
using Unity.VisualScripting;
using UnityEngine;

public class PlayerState
{
    protected PlayerStateMachine stateMachine;
    protected Player player;
    private string animBoolName;

    public PlayerState(PlayerStateMachine stateMachine, Player player, string animBoolName)
    {
        this.stateMachine = stateMachine;
        this.player = player;
        this.animBoolName = animBoolName;
    }

    public virtual void Enter()
    {
        Debug.Log("I enter " + animBoolName);
    }

    public virtual void Update()
    {
        Debug.Log("I'm in " + animBoolName);
    }

    public virtual void Exit()
    {
        Debug.Log("I exit " + animBoolName);
    }
}

PlayerIdleState.cs

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

public class PlayerIdleState : PlayerState
{
    public PlayerIdleState(PlayerStateMachine stateMachine, Player player, string animBoolName) : base(stateMachine, player, animBoolName)
    {
    }

    public override void Enter()
    {
        base.Enter();
    }

    public override void Exit()
    {
        base.Exit();
    }

    public override void Update()
    {
        base.Update();
        if (Input.GetKeyDown(KeyCode.N))
            stateMachine.ChangeState(player.moveState);

    }
}

PlayerMoveState.cs

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

public class PlayerMoveState : PlayerState
{
    public PlayerMoveState(PlayerStateMachine stateMachine, Player player, string animBoolName) : base(stateMachine, player, animBoolName)
    {
    }

    public override void Enter()
    {
        base.Enter();
    }

    public override void Exit()
    {
        base.Exit();
    }

    public override void Update()
    {
        base.Update();
        if (Input.GetKeyDown(KeyCode.N))
            stateMachine.ChangeState(player.idleState);
    }
}

PlayerStateMachine.cs

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

public class PlayerStateMachine
{
    public PlayerState currentState { get; private set; }

    public void Initiallize(PlayerState _startState)
    {
        currentState = _startState;
        currentState.Enter();
    }

    public void ChangeState(PlayerState _newState)
    {
        currentState.Exit();
        currentState = _newState;
        currentState.Enter();
    }

}

Player.cs

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

public class Player : MonoBehaviour
{
    public PlayerStateMachine stateMachine { get; private set; }
    
    public PlayerIdleState idleState { get; private set; }
    public PlayerMoveState moveState { get; private set; }

    private void Awake()
    {
        stateMachine = new PlayerStateMachine();

        idleState = new PlayerIdleState(stateMachine, this, "Idle");
        moveState = new PlayerMoveState(stateMachine, this, "Move");
    }
    private void Start()
    {
        stateMachine.Initiallize(idleState);
    }
    private void Update()
    {
        stateMachine.currentState.Update();
        
    }
}

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