如何同时应用状态模式和策略模式？

Question

我需要用 Java 实现一个播放和录制视频的应用程序。
视频播放器有两种状态，Playing mode 和 recording mode。
在播放模式下，我们可以Play, Pause,Stop, Forward和Backward视频。
另一方面，在录制模式下，我们可以做到Record, Pause或Stop。
这是我到目前为止所做的：br> 我有点卡住了。我不知道我是否应该为每种模式的每个动作创建一个策略，或者我是否可以让它变得更简单。
我正在考虑为PlayingModeVideoPlayer 和RecordingModeVideoPlayer 提供它们的特定策略（多个），但我不知道如何实现它。 谢谢
播放和录制模式是两个独立的东西。我不需要实现这两个实体之间的转换。

Answer 1

注意： 从 OP 来看，尚不清楚它是数字视频播放器，会根据当前模式（播放或录制）自动更改其 UI，还是老式视频带键的播放器（这意味着用户可以在播放模式时点击记录）。

所以，这只是一个可以帮助您前进的想法。

VideoPlayer 界面允许用户开始播放或录制。 When one of these is chosen, the user is handed over a different interface (a contract) that specifies what actions are possible.

public interface VideoPlayer {
    PlayerContext play();
    RecorderContext record();
}

public class PlayerContext {
    private VideoPlayer videoPlayer;
    private PlayerState playerState;

    public PlayerContext(VideoPlayer videoPlayer) {
        this.videoPlayer = videoPlayer;
        //this.playerState = ..init with PlayingState..
    }

    PlayerContext play() {
        playerState.play();
        return this;
    }
    PlayerContext pause() {
        playerState.pause();
        return this;
    }
    VideoPlayer stop() {
        playerState.stop();
        return videoPlayer;
    }
    PlayerContext forward() {
        playerState.forward();
        return this;
    }
    PlayerContext backward() {
        playerState.backward();
        return this;
    }
   //Methods to enable state switching
}


public class RecorderContext {
    private VideoPlayer videoPlayer;
    private RecorderState recorderState;

    public RecorderContext(VideoPlayer videoPlayer) {
        this.videoPlayer = videoPlayer;
        //this.recorderState = ..init with record state
    }

    RecorderContext pause() {
        recorderState.pause();
        return this;
    }
    RecorderContext record() {
        recorderState.record();
        return this;
    }
    VideoPlayer stop() {
        recorderState.stop();
        return videoPlayer;
    }
   //Methods to enable state switching
}

当点击stop 时，用户可以返回并选择两个可用选项之一 - 即可以播放或录制。这就是stop 返回基类VideoPlayer 对象的原因。

public class ConcreteVideoPlayer implements VideoPlayer {

    @Override
    public PlayerContext play() {
        return new PlayerContext(this);
    }

    @Override
    public RecorderContext record() {
        return new RecorderContext(this);
    }
}
public interface PlayerState {
    void play();
    void pause();
    VideoPlayer stop();
    void forward();
    void backward();
}
public interface RecorderState {
    void pause();
    void record();
    VideoPlayer stop();
}

您可以自己实现每个状态实现（PlayerState 和 RecorderState）。

用法：

VideoPlayer videoPlayer = new ConcreteVideoPlayer();
PlayerContext playerContext = videoPlayer.play();
videoPlayer = playerContext.pause()
        .backward()
        .pause()
        .play() //.play() -> Invalid state calls have to be handled by the individual state implementations
        .stop();
RecorderContext recordContext = videoPlayer.record();
videoPlayer = recordContext.pause()
        .record()
        .pause()
        .record()
        .stop();

我希望这会有所帮助！