public interface IState { void Enter(); void Update(); void Exit(); } public class State<T> where T : IState { public delegate void StateAction(T state); public StateAction OnEnter; public StateAction OnUpdate; public StateAction OnExit; public void Enter(T state) { if (OnEnter != null) { OnEnter(state); } } public void Update(T state) { if (OnUpdate != null) { OnUpdate(state); } } public void Exit(T state) { if (OnExit != null) { OnExit(state); } } } public class IdleState : IState { public void Enter() { // Do idle behavior } public void Update() { // Do idle behavior } public void Exit() { // Do idle behavior } } public class WalkingState : IState { public void Enter() { // Do walking behavior } public void Update() { // Do walking behavior } public void Exit() { // Do walking behavior } } public class RunningState : IState { public void Enter() { // Do running behavior } public void Update() { // Do running behavior } public void Exit() { // Do running behavior } } public class StateMachine<T> where T : IState { private Stack<State<T>> stateStack = new Stack<State<T>>(); private T currentState; public void PushState(State<T> newState) { if (currentState != null) { currentState.Exit(); } stateStack.Push(newState); currentState = newState; currentState.Enter(currentState); } public void PopState() { if (stateStack.Count > 0) { currentState.Exit(); stateStack.Pop(); currentState = stateStack.Count > 0 ? stateStack.Peek() : null; if (currentState != null) { currentState.Enter(currentState); } } } public void Update() { if (currentState != null) { currentState.Update(currentState); } } }如何使用，请给出示例代码