设计模式课程 设计模式精讲 27-2 状态模式coding

Posted 2021-03-06 1446358788-qq

1　　　　代码演练

1.1　　代码演练1

 

 

 

 

1　　　　代码演练

1.1　　代码演练1

需求：

课程视频有播放，快进，暂停，停止（关闭）四种状态，状态之间可以相互切换，但是停止状态不能切换到快进 和暂停状态

 

 

重点：（个人开发中没有注意到的地方）

1　　核心：上下文类：this.courseVideoState.setCourseVideoContext(this); 相当于把State 直接把 当前本身状态 直接放到 上下文（CourseVideoContext）中

2　　重点：状态基类：因为要被子类所使用的属性，所以权限设置成protected

 

 

uml类图：

 

 

测试类：

package com.geely.design.pattern.behavioral.state;

public class Test {

    @org.junit.Test
    public void testVideoState(){

        CourseVideoContext courseVideoContext = new CourseVideoContext();
        courseVideoContext.setCourseVideoState(new PlayState());

        System.out.println("目前状态为："+courseVideoContext.getCourseVideoState().getClass().getSimpleName());

        courseVideoContext.Pause();
        System.out.println("目前状态为："+courseVideoContext.getCourseVideoState().getClass().getSimpleName());

        courseVideoContext.Speed();
        System.out.println("目前状态为："+courseVideoContext.getCourseVideoState().getClass().getSimpleName());


        courseVideoContext.Stop();
        System.out.println("目前状态为："+courseVideoContext.getCourseVideoState().getClass().getSimpleName());

        courseVideoContext.Speed();
        System.out.println("目前状态为："+courseVideoContext.getCourseVideoState().getClass().getSimpleName());
    }
}

 

 

 

视频状态基类：

package com.geely.design.pattern.behavioral.state;

public abstract class CourseVideoState {
    //重点：因为要被子类所使用的属性，所以权限设置成protected
    protected  CourseVideoContext courseVideoContext;

    public void setCourseVideoContext(CourseVideoContext courseVideoContext) {
        this.courseVideoContext = courseVideoContext;
    }

    public abstract void play();
    public abstract void speed();
    public abstract void pause();
    public abstract void stop();

}

 

上下文类：

package com.geely.design.pattern.behavioral.state;

public class CourseVideoContext {
    private CourseVideoState courseVideoState;
    public final static PlayState PLAY_STATE = new PlayState();
    public final static PauseState PAUSE_STATE = new PauseState();
    public final static SpeedState SPEED_STATE = new SpeedState();
    public final static StopState STOP_STATE = new StopState();

    //注意这里是get方法，不是构造器
    public CourseVideoState getCourseVideoState() {
        return courseVideoState;
    }

    /**
     * 核心：重点：this.courseVideoState.setCourseVideoContext(this); 相当于把State 直接把 当前本身状态 直接放到 上下文（CourseVideoContext）中
     * @param courseVideoState
     */
    public void setCourseVideoState(CourseVideoState courseVideoState) {
        this.courseVideoState = courseVideoState;
        this.courseVideoState.setCourseVideoContext(this);
    }

    public void Play(){
        this.courseVideoState.play();
    }

    public void Pause(){
        this.courseVideoState.pause();
    }

    public void Speed(){
        this.courseVideoState.speed();
    }

    public void Stop(){
        this.courseVideoState.stop();
    }
}

 

播放状态类：

package com.geely.design.pattern.behavioral.state;

public class PlayState extends CourseVideoState {
    @Override
    public void play() {
        System.out.println("开始播放");
    }

    @Override
    /**
     * 此处方法需要仔细看
     * 通过 上下文来设置课程视频状态
     */
    public void speed() {
        super.courseVideoContext.setCourseVideoState(CourseVideoContext.SPEED_STATE);
    }

    @Override
    public void pause() {
        super.courseVideoContext.setCourseVideoState(CourseVideoContext.PAUSE_STATE);
    }

    @Override
    public void stop() {
        super.courseVideoContext.setCourseVideoState(CourseVideoContext.STOP_STATE);
    }
}

 

暂停状态类：

package com.geely.design.pattern.behavioral.state;

public class PauseState extends CourseVideoState {
    @Override
    public void play() {
        super.courseVideoContext.setCourseVideoState(CourseVideoContext.PLAY_STATE);
    }

    @Override
    public void speed() {
        super.courseVideoContext.setCourseVideoState(CourseVideoContext.SPEED_STATE);
    }

    @Override
    public void pause() {
        System.out.println("处于暂停状态");
    }

    @Override
    public void stop() {
        super.courseVideoContext.setCourseVideoState(CourseVideoContext.STOP_STATE);
    }
}

 

快进状态类：

package com.geely.design.pattern.behavioral.state;

public class SpeedState extends CourseVideoState {
    @Override
    public void play() {
        super.courseVideoContext.setCourseVideoState(CourseVideoContext.PLAY_STATE);
    }

    @Override
    public void speed() {
        System.out.println("处于快进状态");
    }

    @Override
    public void pause() {
        super.courseVideoContext.setCourseVideoState(CourseVideoContext.PAUSE_STATE);
    }

    @Override
    public void stop() {
        super.courseVideoContext.setCourseVideoState(CourseVideoContext.STOP_STATE);
    }
}

 

停止状态类：

package com.geely.design.pattern.behavioral.state;

public class StopState extends CourseVideoState {
    @Override
    public void play() {
        super.courseVideoContext.setCourseVideoState(CourseVideoContext.PLAY_STATE);
    }

    @Override
    public void speed() {
        System.out.println("ERROR 关闭状态 不能切换到 快进状态");
    }

    @Override
    public void pause() {
        System.out.println("ERROR 关闭状态 不能切换到 暂停状态");
    }

    @Override
    public void stop() {
        System.out.println("已关闭");
    }
}

 

 

打印日志：

目前状态为：PlayState
目前状态为：PauseState
目前状态为：SpeedState
目前状态为：StopState
ERROR 关闭状态 不能切换到 快进状态
目前状态为：StopState

Process finished with exit code 0