状态模式

保存所有操作流程接口 

package com.godv.state;
//状态接口
public interface State {
	/**
     * 重置
     */
    void reset(Context context);

    /**
     * 设置数据源
     */
    void setDataSource(Context context);

    /**
     * 异步准备
     */
    void prepareAsync(Context context);

    /**
     * 停止
     */
    void stop(Context context);

    /**
     * seek
     */
    void seekTo(Context context);

    /**
     * 开始播放
     */
    void start(Context context);

    /**
     * 暂停
     */
    void pause(Context context);

    String getCurrentState();
}

封装接口重写方法  使需要的类重写抽象类方法 

package com.godv.state;

public abstract class AbstractState implements State {

	protected static final RuntimeException EXCEPTION = new RuntimeException("操作流程不允许");

	@Override
	public void reset(Context context) {
		// TODO Auto-generated method stub
		throw EXCEPTION;
	}

	@Override
	public void setDataSource(Context context) {
		// TODO Auto-generated method stub
		throw EXCEPTION;
	}

	@Override
	public void prepareAsync(Context context) {
		// TODO Auto-generated method stub
		throw EXCEPTION;
	}

	@Override
	public void stop(Context context) {
		// TODO Auto-generated method stub
		throw EXCEPTION;
	}

	@Override
	public void seekTo(Context context) {
		// TODO Auto-generated method stub
		throw EXCEPTION;
	}

	@Override
	public void start(Context context) {
		// TODO Auto-generated method stub
		throw EXCEPTION;
	}

	@Override
	public void pause(Context context) {
		// TODO Auto-generated method stub
		throw EXCEPTION;
	}
}

具体的实现类

package com.godv.state;

class Idle extends AbstractState {

	@Override
	public void reset(Context context) {
		// TODO Auto-generated method stub
		context.setState(new Idle());
	}

	@Override
	public void setDataSource(Context context) {
		// TODO Auto-generated method stub
		context.setState(new Initialized());
	}

	@Override
	public String getCurrentState() {
		// TODO Auto-generated method stub
		return StateEnum.IDLE.getValue();
	}

}

class Initialized extends AbstractState {
	
	@Override
	public void reset(Context context) {
		// TODO Auto-generated method stub
		context.setState(new Idle());
	}

	@Override
	public void prepareAsync(Context context) {
		// TODO Auto-generated method stub
		context.setState(new Prepard());
	}
	
	@Override
	public String getCurrentState() {
		// TODO Auto-generated method stub
		return StateEnum.INITIALIZED.getValue();
	}
}

class Prepard extends AbstractState {

	@Override
	public void reset(Context context) {
		// TODO Auto-generated method stub
		context.setState(new Idle());
	}

	@Override
	public void stop(Context context) {
		// TODO Auto-generated method stub
		context.setState(new Stopped());
	}

	@Override
	public void seekTo(Context context) {
		// TODO Auto-generated method stub
		context.setState(new Stopped());
	}

	@Override
	public void start(Context context) {
		// TODO Auto-generated method stub
		context.setState(new Started());
	}

	@Override
	public String getCurrentState() {
		// TODO Auto-generated method stub
		return StateEnum.PREPARED.getValue();
	}
}

class Started extends AbstractState {

	@Override
	public void reset(Context context) {
		// TODO Auto-generated method stub
		context.setState(new Idle());
	}

	@Override
	public void stop(Context context) {
		// TODO Auto-generated method stub
		context.setState(new Stopped());
	}

	@Override
	public void seekTo(Context context) {
		// TODO Auto-generated method stub
		context.setState(new Started());
	}

	@Override
	public void start(Context context) {
		// TODO Auto-generated method stub
		context.setState(new Started());
	}

	@Override
	public void pause(Context context) {
		// TODO Auto-generated method stub
		context.setState(new Pause());
	}

	@Override
	public String getCurrentState() {
		return StateEnum.STARTED.getValue();
	}

}

class Stopped extends AbstractState {

	@Override
	public void reset(Context context) {
		// TODO Auto-generated method stub
		context.setState(new Idle());
	}

	@Override
	public void prepareAsync(Context context) {
		// TODO Auto-generated method stub
		context.setState(new Prepard());
	}

	@Override
	public void stop(Context context) {
		// TODO Auto-generated method stub
		context.setState(new Stopped());
	}

	@Override
	public String getCurrentState() {
		return StateEnum.STOPPED.getValue();
	}

}

class Pause extends AbstractState {

	@Override
	public void stop(Context context) {
		// TODO Auto-generated method stub
		context.setState(new Stopped());
	}

	@Override
	public void seekTo(Context context) {
		// TODO Auto-generated method stub
		context.setState(new Pause());
	}

	@Override
	public void pause(Context context) {
		// TODO Auto-generated method stub
		context.setState(new Pause());
	}

	@Override
	public String getCurrentState() {
		return StateEnum.PAUSE.getValue();
	}

}

目标操作类

package com.godv.state;

public class Context extends AbstractState{
	
	private State state = new Idle();

    @Override
	public void reset(Context context) {
		// TODO Auto-generated method stub
    	state.reset(context);
    	getCurrentState();
	}

	@Override
	public void setDataSource(Context context) {
		// TODO Auto-generated method stub
		state.setDataSource(context);
		getCurrentState();
	}

	@Override
	public void prepareAsync(Context context) {
		// TODO Auto-generated method stub
		state.prepareAsync(context);
		getCurrentState();
	}

	@Override
	public void stop(Context context) {
		// TODO Auto-generated method stub
		state.stop(context);
		getCurrentState();
	}

	@Override
	public void seekTo(Context context) {
		// TODO Auto-generated method stub
		state.seekTo(context);
		getCurrentState();
	}

	@Override
	public void start(Context context) {
		// TODO Auto-generated method stub
		state.start(context);
		getCurrentState();
	}

	@Override
	public void pause(Context context) {
		// TODO Auto-generated method stub
		state.pause(context);
		getCurrentState();
	}

	public State getState() {
        return state;
    }

    public void setState(State state) {
        this.state = state;
    }

    @Override
    public String getCurrentState() {
        System.out.println("当前状态 : " + state.getCurrentState());
        return state.getCurrentState();
    }
}

状态Enum

package com.godv.state;

public enum StateEnum {
	//播放器就绪
    IDLE(1, "IDLE"),

    //初始化状态
    INITIALIZED(2, "INITIALIZED"),

    //就绪
    PREPARED(3, "PREPARED"),

    //开始播放状态
    STARTED(4, "STARTED"),

    //暂停状态
    PAUSE(5, "PAUSE"),

    //停止状态
    STOPPED(6, "FEED_BACKED");

    private int key;
    private String value;

    StateEnum(int key, String value) {
        this.key = key;
        this.value = value;
    }
    public int getKey() {return key;}
    public String getValue() {return value;}
}

测试

package com.godv.state;

public class Client {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Context context = new Context();
		System.out.println(context.getCurrentState());
		context.prepareAsync(context); //异常
	}
}