游戏AI：（二）状态机

一个状态机分为四种状态：状态输入、状态进入、状态更新、状态退出。

案例：现在我们要实现主角的移动、跳跃、攻击之间的状态切换。

1）先把动画控制器做好

  2）开始写脚本了，我们先写一个状态基类：定义状态进入、状态更新、状态退出（虚方法，以便在状态子类中重写），初始化（让每个状态脚本获取到animator跟管理者）

public enum PlayerState
{
    Idle,
    Run,
    Jump,
    AttackA,
    AttackB,
    AttackC
}
public class PlayerStateBase : MonoBehaviour
{
    public PlayerStateManager manager;
    public Animator animator;
    public virtual void Init()
    {
        animator = GetComponent<Animator>();
        manager = GetComponent<PlayerStateManager>();
    }
    //状态进入
    public virtual void OnEnter() { }
    //状态更新
    public virtual void OnUpdate() { }
    //状态退出
    public virtual void OnExit() { }
}

2）再写负责状态切换的管理者类

public class PlayerStateManager : MonoBehaviour
{
    Dictionary<Type, PlayerStateBase> states = new Dictionary<Type, PlayerStateBase>();
    PlayerStateBase currentState;
    private void Awake()
    {
        AddState<PlayerStateIdle>();
        AddState<PlayerStateRun>();
        AddState<PlayerStateJump>();
        AddState<PlayerStateAttackA>();
        AddState<PlayerStateAttackB>();
        AddState<PlayerStateAttackC>();
        ChangeState<PlayerStateIdle>();
    }
    private void AddState<T>() where T : PlayerStateBase
    {
        PlayerStateBase state = gameObject.AddComponent<T>();
        state.Init();
        states.Add(typeof(T), state);
    }
    public void ChangeState<T>() where T : PlayerStateBase
    {
        if (currentState != null)
            currentState.OnExit();
        currentState = states[typeof(T)];
        currentState.OnEnter();
    }
    private void Update()
    {
        if (currentState != null)
            currentState.OnUpdate();
    }
}

3）然后是针对每种状态创建一个脚本

a. Idle 站立状态

public class PlayerStateIdle : PlayerStateBase
{
    private float h;
    private float v;

    public override void OnEnter()
    {
        animator.SetBool("Run", false);
    }
    public override void OnUpdate()
    {
        if (Input.GetKeyDown(KeyCode.Alpha1))
        {
            manager.ChangeState<PlayerStateAttackA>();
            return;
        }
        if (Input.GetKeyDown(KeyCode.Alpha2))
        {
            manager.ChangeState<PlayerStateAttackB>();
            return;
        }
        if (Input.GetKeyDown(KeyCode.Alpha3))
        {
            manager.ChangeState<PlayerStateAttackC>();
            return;
        }
        if (Input.GetKeyDown(KeyCode.Space))
        {
            manager.ChangeState<PlayerStateJump>();
            return;
        }

        h = Input.GetAxis("Horizontal");
        v = Input.GetAxis("Vertical");
        if (h != 0 || v != 0)
        {
            manager.ChangeState<PlayerStateRun>();
            return;
        }
    }
}

b. Run 奔跑状态

public class PlayerStateRun : PlayerStateBase
{
    private float h;
    private float v;
    private Vector3 direction;
    private CharacterController cc;

    public override void Init()
    {
        base.Init();
        cc = GetComponent<CharacterController>();
    }
    public override void OnEnter()
    {
        animator.SetBool("Run", true);
    }
    public override void OnUpdate()
    {
        if (Input.GetKeyDown(KeyCode.Alpha1))
        {
            manager.ChangeState<PlayerStateAttackA>();
            return;
        }
        if (Input.GetKeyDown(KeyCode.Alpha2))
        {
            manager.ChangeState<PlayerStateAttackB>();
            return;
        }
        if (Input.GetKeyDown(KeyCode.Alpha3))
        {
            manager.ChangeState<PlayerStateAttackC>();
            return;
        }
        if (Input.GetKeyDown(KeyCode.Space))
        {
            manager.ChangeState<PlayerStateJump>();
            return;
        }
        h = Input.GetAxis("Horizontal");
        v = Input.GetAxis("Vertical");
        direction.Set(h, 0, v);
        if (h == 0 && v == 0)
        {
            manager.ChangeState<PlayerStateIdle>();
            return;
        }
        direction = Camera.main.transform.TransformDirection(direction);
        direction.y = 0;
        transform.rotation = Quaternion.LookRotation(direction);
        cc.SimpleMove(direction * 3.0f);
    }
}

c. Jump 跳跃状态

public class PlayerStateJump : PlayerStateBase
{
    private Vector3 startPos;
    private Vector3 endPos;
    bool isJump;
    public override void OnEnter()
    {
        startPos = transform.position;
        endPos = startPos + transform.forward * 5.0f;
        isJump = true;
        animator.SetTrigger("Jump");
    }
    public override void OnUpdate()
    {
        AnimatorStateInfo info = animator.GetCurrentAnimatorStateInfo(0);
        if (info.IsName("Jump"))
            return;
        if (isJump && info.normalizedTime > 0.2f)
        {
            transform.position = Vector3.Lerp(startPos, endPos, info.normalizedTime);
            if (info.normalizedTime > 0.7f)
                isJump = false;
        }
        if (info.normalizedTime > 0.9f)
            manager.ChangeState<PlayerStateIdle>();
    }
}

d. Attack 攻击状态（这里只展示一个，另外两个是一样的）

public class PlayerStateAttackA : PlayerStateBase
{
    public override void OnEnter()
    {
        animator.SetTrigger("AttackA");
    }
    public override void OnUpdate()
    {
        AnimatorStateInfo info = animator.GetCurrentAnimatorStateInfo(0);
        if (info.IsName("AttackA"))
            return;
        
        if (info.normalizedTime > 0.9f)
            manager.ChangeState<PlayerStateIdle>();
    }
}