c# - 使用状态模式的分层状态机的最佳实践是什么？

Question

我即将使用状态模式在 C# 中实现分层状态机。作为指南，我使用 this例子。不过，该示例并未提供有关分层状态的答案。不幸的是，我似乎无法在别处找到好的例子。我的第一个想法是为分层状态创建嵌套分类。但这被认为是最佳实践还是有更好的解决方案？

您好!

更新:

我整个下午都在尝试实现上述状态模式。 HSM 基于一个非常简单的媒体播放器:

alt text http://www.freeimagehosting.net/uploads/e8d2d6486a.jpg

我以为我已经做到了，但有一件事我不明白。首先是我写的代码(抱歉，太多了):

public class MediaPlayer
{
    public MediaPlayerStates state;

    public MediaPlayer(MediaPlayerStates state)
    {
        this.state = state;
    }

    public void OnButtonPressed()
    {
        state.OnButtonPressed(this);
    }

    public void DeviceBooted()
    { 
        state. ?????
    }

    //Other Functions
}

//The 3 initial states (Start, On, End) know only 2 events.
public abstract class MediaPlayerStates
{
    public abstract void OnButtonPressed(MediaPlayer player);
    public abstract void OffButtonPressed(MediaPlayer player);
}

//The very beginpoint of the state machine
public class Start : MediaPlayerStates
{
    //When hitting the onbutton, the state changes to the OnState state
    public override void OnButtonPressed(MediaPlayer player)
    {
        player.state = new OnState(player);
    }

    //No need to implement this one
    public override void OffButtonPressed(MediaPlayer player)
    {
        throw new NotImplementedException();
    }
}

//OnState implements the 2 events from the MediaPlayerStates abstract class.
public class OnState : MediaPlayerStates
{
    //When entered the OnState state, a new entrypoint is creaeted: the Start state
    public OnState(MediaPlayer player)
    {
        player.state = new OnStartState();
    }

    //The OnState doesn't have a OnButtonPressed event so it doesn't need to be implemented
    public override void OnButtonPressed(MediaPlayer player)
    {
        throw new NotImplementedException();
    }

    //When hitting the offbutton in the OnState, the new state is End
    public override void OffButtonPressed(MediaPlayer player)
    {
        player.state = new End();
    }

    //The OnState itself containts 3 events, therefore these need to be implemented by every state whitin the OnState state
    public abstract class SubStates : MediaPlayerStates
    {
        public abstract void DeviceBooted(MediaPlayer player);
        public abstract void PlayButtonPressed(MediaPlayer player);
        public abstract void StopButtonPressed(MediaPlayer player);
    }

    //The OnStartState is the pseudoState where the On state starts
    public class OnStartState : SubStates
    {
        //When booted, the state of the player changes to the ShowMediaFileState state
        public override void DeviceBooted(MediaPlayer player)
        {
            player.state = new ShowMediaFileState();
        }

        //The events below don't need to be implemented since they don't exist. 
        public override void PlayButtonPressed(MediaPlayer player)
        {
            throw new NotImplementedException();
        }

        public override void StopButtonPressed(MediaPlayer player)
        {
            throw new NotImplementedException();
        }

        public override void OnButtonPressed(MediaPlayer player)
        {
            throw new NotImplementedException();
        }

        public override void OffButtonPressed(MediaPlayer player)
        {
            throw new NotImplementedException();
        }
    }

    public class ShowMediaFileState : SubStates
    {
        //This event doesn't exists for this state
        public override void DeviceBooted(MediaPlayer player)
        {
            throw new NotImplementedException();
        }

        //When hitting the play button in this state, play the mediafile
        public override void PlayButtonPressed(MediaPlayer player)
        {
            player.state = new PlayMediaFileState();
        }

        //These events also don't exist for this state
        public override void StopButtonPressed(MediaPlayer player)
        {
            throw new NotImplementedException();
        }

        public override void OnButtonPressed(MediaPlayer player)
        {
            throw new NotImplementedException();
        }

        public override void OffButtonPressed(MediaPlayer player)
        {
            throw new NotImplementedException();
        }
    }

    public class PlayMediaFileState : SubStates
    {
        //This event doesn't exist for this state
        public override void DeviceBooted(MediaPlayer player)
        {
            throw new NotImplementedException();
        }

        //This event doesn't exist for this state
        public override void PlayButtonPressed(MediaPlayer player)
        {
            throw new NotImplementedException();
        }

        //While playing a file and hitting the stopbutton, the state changes to the ShowMediaFileState state
        public override void StopButtonPressed(MediaPlayer player)
        {
            player.state = new ShowMediaFileState();
        }

        //This event doesn't exist for this state
        public override void OnButtonPressed(MediaPlayer player)
        {
            throw new NotImplementedException();
        }

        //This event doesn't exist for this state
        public override void OffButtonPressed(MediaPlayer player)
        {
            throw new NotImplementedException();
        }
    }
}

//The endstate doesn't need any implementation since there cannot occur a event while being off
public class End : MediaPlayerStates
{
    public override void OnButtonPressed(MediaPlayer player)
    {
        throw new NotImplementedException();
    }

    public override void OffButtonPressed(MediaPlayer player)
    {
        throw new NotImplementedException();
    }
}

在 MediaPlayer 类中定义事件时，我无法调用任何其他函数

• OnButtonPressed
• OffButtonPressed

所以我想知道，我的实现效果好吗？怎么了？我还尝试查看使用复合模式的建议，但我不明白它应该如何与状态模式一起使用。希望大家帮忙!

Answer 1

我认为您也需要 Composite；这将使您能够将状态机链接在一起。