文章目录
状态模式(有限状态机)结构实现(有限状态机)应用场景优缺点与其他模式的关系状态模式(有限状态机)
状态模式是一种对象型模式,他将复杂的逻辑判断提取到不同状态对象中,允许状态对象在其内部状态发生改变时,改变其行为。状态的改变和各个状态的行为是状态模式的核心。
这里模式就需要谈到一个游戏中经常使用的状态模式的形式。它就是有限状态机,有限状态机是作为对象不同状态的管理而使用的(游戏AI也经常使用有限状态机)。其主要思想是程序在任意时刻仅可处在有限的几个状态中。在任意状态中,程序行为将随状态的改变,发生改变。而状态和状态之间的切换都是预先设计好的。
预先定义的状态切换规则称为转移。
结构
说明
状态接口 - 定义状态的行为和状态切换具体状态 - 实现状态的行为和状态切换系统 - 负责状态的切换和状态的实际调用以及状态的管理。
实现(有限状态机)
这里将实现一个有限状态机,状态机分为四个部分
状态枚举状态接口及状态类条件接口及条件类状态系统
我们使用了泛型来增强有限状态机的复用性,使用工厂来创建状态机(避免复杂的创建过程,停留在调用端来污染代码)
为了方便考虑,我只枚举了 Idle(闲置)和 Chase(追击)两种状态
第一部分
状态枚举
public enum StateId{Idle,Chase,}
第二部分
状态接口
public interface IState<T>where T : Enum{//获得对应状态类的IdT Id {get; }//状态进入前,调用此函数void OnEnterState();//状态时,调用此函数void OnUpdateState();//状态退出前,调用此函数void OnExitState();//状态转换函数,通过此函数判断是否转移状态bool TransitionState(out T id);}
敌人抽象状态
public abstract class EnemyState : IState<StateId>{private readonly StateId _id;private readonly ITransitionState<StateId> _transitionState;protected EnemyState(StateId id, ITransitionState<StateId> transitionState){_id = id;_transitionState = transitionState;}public StateId Id => _id;public virtual void OnEnterState() {}public abstract void OnUpdateState();public virtual void OnExitState() {}public bool TransitionState(out StateId id) => _transitionState.Transition(out id);}
之所以多出来这个抽象类,是为了将状态条件逻辑和状态行为逻辑分开,使得子类无需关注状态转移,只关注实现即可。而状态的转移实现转交给条件类完成(实现状态判断和状态行为实现的分离)。
具体状态类(Idle,Chase)
public class EnemyIdleState : EnemyState{public EnemyIdleState(ITransitionState<StateId> transitionState) : base(StateId.Idle, transitionState){}public override void OnUpdateState(){}}
public class EnemyChaseState : EnemyState{private float _chaseSpeed;private float _chaseRange;private GameObject _go;private GameObject _chaseTarget;//物理缓存private Collider[] _colliders = new Collider[1];public EnemyChaseState(float chaseSpeed, float chaseRange, GameObject go, ITransitionState<StateId> transitionState) : base(StateId.Chase, transitionState){_go = go;_chaseSpeed = chaseSpeed;_chaseRange = chaseRange;}public override void OnEnterState(){_chaseTarget = null;int num = Physics.OverlapSphereNonAlloc(_go.transform.position, _chaseRange,_colliders, 1 << LayerMask.NameToLayer("Player"));if (num != 0) _chaseTarget = _colliders[0].gameObject;}public override void OnUpdateState(){//移动var position = _go.transform.position;position += _chaseSpeed * Time.deltaTime * (_chaseTarget.transform.position - position).normalized;_go.transform.position = position;//旋转_go.transform.LookAt(_chaseTarget.transform);}public override void OnExitState(){_chaseTarget = null;}}
第三部分
条件接口
public interface ITransitionState<T>where T : Enum{bool Transition(out T id);}
具体条件接口(IdleTransition,Chase Transition)
public class EnemyIdleStateTransition : ITransitionState<StateId>{//自身游戏对象private GameObject _go;//侦察范围private float _scoutingRange;//侦察范围间隔(每帧调用,不利于程序性能)private readonly float _scoutingTime = 0.2f;private float _currentTime;public EnemyIdleStateTransition(GameObject go, float scoutingRange){_scoutingRange = scoutingRange;_go = go;}public bool Transition(out StateId id){_currentTime += Time.deltaTime;if (_currentTime >= _scoutingTime){_currentTime = 0f;if (Physics.CheckSphere(_go.transform.position, _scoutingRange, 1 << LayerMask.NameToLayer("Player"))){id = StateId.Chase;return true;}}id = StateId.Idle;return false;}}
public class EnemyChaseStateTransition : ITransitionState<StateId>{//脱离追击的距离private float _outChaseDistance;//自身游戏对象private GameObject _go;//脱离范围间隔(每帧调用不利于程序性能)private readonly float _outChaseTime = 0.2f;private float _currentTime;public EnemyChaseStateTransition(GameObject go, float outChaseDistance){_outChaseDistance = outChaseDistance;_go = go;}public bool Transition(out StateId id){_currentTime += Time.deltaTime;if (_currentTime >= _outChaseTime){_currentTime = 0f;if (!Physics.CheckSphere(_go.transform.position, _outChaseDistance, 1 << LayerMask.NameToLayer("Player"))){id = StateId.Idle;return true;}}id = StateId.Chase;return false;}}
第四部分
有限状态机系统类
public class FsmSystem<T>where T : Enum{private Dictionary<T, IState<T>> _stateDic;private T _currentStateId;private IState<T> _currentState;public T Id => _currentStateId;public FsmSystem(){_stateDic = new Dictionary<T, IState<T>>();}public void Add(IState<T> state){if (state == null) return;if (_stateDic.ContainsKey(state.Id)) return;_stateDic.Add(state.Id, state);}public void Remove(T id){if (!_stateDic.ContainsKey(id)) return;_stateDic.Remove(id);}public bool Enable(T id){if (!_stateDic.ContainsKey(id)) return false;_currentStateId = id;_currentState = _stateDic[id];_currentState.OnEnterState();return true;}public void Update(){if (_currentState.TransitionState(out T id))TransferState(id);_currentState.OnUpdateState();}//转移状态函数private void TransferState(T id){if (!_stateDic.ContainsKey(id)) return;_currentState.OnExitState();_currentState = _stateDic[id];_currentStateId = id;_currentState.OnEnterState();}}
工厂类
public class FsmFactory{public static FsmSystem<StateId> CreateEnemyFsm(GameObject go, float chaseRange, float chaseSpeed, float outChaseRange){var fsm = new FsmSystem<StateId>();//创建条件,并添加条件所需对应参数var idleStateTransition = new EnemyIdleStateTransition(go, chaseRange);var chaseStateTransition = new EnemyChaseStateTransition(go, outChaseRange);//创建状态,并添加状态所需参数,而且将条件与状态绑定var idleState = new EnemyIdleState(idleStateTransition);var chaseState = new EnemyChaseState(chaseSpeed, chaseRange, go, chaseStateTransition);fsm.Add(idleState);fsm.Add(chaseState);fsm.Enable(StateId.Idle);return fsm;}}
调用端
public class StateExample : MonoBehaviour{//追击速度[SerializeField] private float _chaseSpeed = 3.0f;//追击范围[SerializeField] private float _chaseRange = 4.0f;//脱离追击距离[SerializeField] private float _outChaseRange = 5.0f;//此时状态[SerializeField] private StateId _stateId;private FsmSystem<StateId> _system;private void Awake(){_system = FsmFactory.CreateEnemyFsm(gameObject, _chaseRange, _chaseSpeed, _outChaseRange);}private void Update(){_system.Update();_stateId = _system.Id;}}
将玩家对象设置为 Player 层
效果图
由于不会作动图只能将就这看吧,代码没有问题,效果也还不错。
应用场景
游戏敌人AI需要根据不同状态进行改变,有不同行为。如果某个类需要根据成员变量的当前值改变自身行为,需要大量的判断条件时,可以使用状态模式。优缺点
优点
将状态分离,单一职责原则简化条件的判断
缺点
实现过于繁琐类数量过多,容易造成系统复杂