转载请注明地址:凉鞋的笔记
为什么用有限状态机?
之前做过一款跑酷游戏,跑酷角色有很多状态:跑、跳、二段跳、死亡等等。一开始是使用if/switch来切换状态,但是每次角色添加一个状态（提前没规划好),所有状态处理相关的代码就会指数级增长,那样就会嗅出代码的坏味道了。在这种处理状态并且状态数量不是特别多的情况下,自然就想到了引入状态机。
优点:
1.使代码整洁,状态容易扩展和管理。
2.可复用。
3.还没想到.....
缺点:
1.也没想到......
什么是有限状态机?
解释不清楚,看了下百度百科。反正是一种数据结构,一个解决问题的工具。
从百度百科可以看到,有限状态机最最最基础的概念有两个:状态和转移。
从刚才跑酷的例子来讲,跑、跳、二段跳等这些就是角色的状态。
如图所示:
主角从跑状态切换到跳状态,从跳状态切换到二段跳状态,这里的切换就是指状态的转移。状态的转移是有条件的,比如主角从跑状态不可以直接切换到二段跳状态。但是可以从二段跳状态切换到跑状态。
另外,一个基本的状态有:进入状态、退出状态、接收输入、转移状态等动作。但是仅仅作为跑酷的角色的状态管理来说,只需要转移状态就足够了。有兴趣的同学可以自行扩展。
如何实现?
恰好之前看到过一个还算简易的实现(简易就是指我能看得懂- -,希望大家也是),原版是用lua实现的,我的跑酷游戏是用C#实现的,所以直接贴出C#代码。
using UnityEngine;
using System.Collections;
using System.Collections.Generic;
public class FSM {
// 定义函数指针类型
public delegate void FSMTranslationCallfunc(); /// <summary>
/// 状态类
/// </summary>
public class FSMState
{
public string name;
public FSMState(string name)
{
this.name = name;
}
/// <summary>
/// 存储事件对应的条转
/// </summary>
public Dictionary <string,FSMTranslation> TranslationDict = new Dictionary<string,FSMTranslation>();
}
/// <summary>
/// 跳转类
/// </summary>
public class FSMTranslation
{
public FSMState fromState;
public string name;
public FSMState toState;
public FSMTranslationCallfunc callfunc; // 回调函数
public FSMTranslation(FSMState fromState,string name, FSMState toState,FSMTranslationCallfunc callfunc)
{
this.fromState = fromState;
this.toState = toState;
this.name = name;
this.callfunc = callfunc;
}
}
// 当前状态
private FSMState mCurState;
Dictionary <string,FSMState> StateDict = new Dictionary<string,FSMState>();
/// <summary>
/// 添加状态
/// </summary>
/// <param name="state">State.</param>
public void AddState(FSMState state)
{
StateDict [state.name] = state;
}
/// <summary>
/// 添加条转
/// </summary>
/// <param name="translation">Translation.</param>
public void AddTranslation(FSMTranslation translation)
{
StateDict [translation.fromState.name].TranslationDict [translation.name] = translation;
}
/// <summary>
/// 启动状态机
/// </summary>
/// <param name="state">State.</param>
public void Start(FSMState state)
{
mCurState = state;
}
/// <summary>
/// 处理事件
/// </summary>
/// <param name="name">Name.</param>
public void HandleEvent(string name)
{
if (mCurState != null && mCurState.TranslationDict.ContainsKey(name)) {
Debug.LogWarning ("fromState:" + mCurState.name);
mCurState.TranslationDict [name].callfunc ();
mCurState = mCurState.TranslationDict [name].toState;
Debug.LogWarning ("toState:" + mCurState.name);
}
}
}
测试代码(需自行修改):
// Idle, 闲置
// Run, 跑
// Jump, 一段跳
// DoubleJump, 二段跳
// Die, 挂彩
// 创建状态
FSM.FSMState idleState = new FSM.FSMState("idle");
FSM.FSMState runState = new FSM.FSMState("run");
FSM.FSMState jumpState = new FSM.FSMState("jump");
FSM.FSMState doubleJumpState = new FSM.FSMState("double_jump");
FSM.FSMState dieState = new FSM.FSMState("die");
// 创建跳转
FSM.FSMTranslation touchTranslation1 = new FSM.FSMTranslation(runState,"touch_down",jumpState,Jump);
FSM.FSMTranslation touchTranslation2 = new FSM.FSMTranslation(jumpState,"touch_down",doubleJumpState,DoubleJump);
FSM.FSMTranslation landTranslation1 = new FSM.FSMTranslation(jumpState,"land",runState,Run);
FSM.FSMTranslation landTranslation2 = new FSM.FSMTranslation(doubleJumpState,"land",runState,Run);
// 添加状态
PlayerModel.Instance ().fsm.AddState (idleState);
PlayerModel.Instance ().fsm.AddState (runState);
PlayerModel.Instance ().fsm.AddState (jumpState);
PlayerModel.Instance ().fsm.AddState (doubleJumpState);
PlayerModel.Instance ().fsm.AddState (dieState);
// 添加跳转
PlayerModel.Instance ().fsm.AddTranslation (touchTranslation1);
PlayerModel.Instance ().fsm.AddTranslation (touchTranslation2);
PlayerModel.Instance ().fsm.AddTranslation (landTranslation1);
PlayerModel.Instance ().fsm.AddTranslation (landTranslation2);
PlayerModel.Instance ().fsm.Start (runState);
贴上代码地址址:https://github.com/liangxiegame/QFramework/blob/master/Script/DesignPattern/QFSM.cs
就这些,想要进一步扩展的话,可以给FSMState类添加EnterCallback和ExitCallback等委托,然后在FSM的HandleEvent方法中进行调用。当时对跑酷的项目来说够用了,接没继续扩展了,我好懒- -,懒的借口是:没有最好的设计,只有最适合的设计。
