第14章《观察者模式》

发布时间：2020-12-13 20:56:09 所属栏目：百科来源：网络整理

导读：的依赖关系，让多个观察者对象同事监听某一个主题的对象。这个主题对象在状态在发生变化时，会通知所有的观察者对象，让它们能够。 /** @Author: cxh @CreateTime: 18/1/10 09:08 @ProjectName: JavaBaseTest */ public class Client { public static void

的依赖关系，让多个观察者对象同事监听某一个主题的对象。这个主题对象在状态在发生变化时，会通知所有的观察者对象，让它们能够。

/**


@Author: cxh


@CreateTime: 18/1/10 09:08


@ProjectName: JavaBaseTest

*/

public class Client {

public static void main(String[] args) {

Boss boss=new Boss();

NBAObserver nbaObserver=new NBAObserver("李明浩",boss);

TVObserver tvObserver=new TVObserver("李沁",boss);

//add

boss.add(nbaObserver);

boss.add(tvObserver);

//delete
 //boss状态转变,通知观察者
 boss.setSubjetctState("领导回来了");
 boss.notifyObservers();
}

}



/**


@Author: cxh


@CreateTime: 18/1/9 23:29


@ProjectName: JavaBaseTest

*/

public abstract class Subject {

abstract void add(Observer observer);

abstract void delete(Observer observer);

abstract void notifyObservers();

private String subjetctState;
//获取主题状态

public String getSubjetctState() {

return subjetctState;

}

//设置主题状态

public void setSubjetctState(String subjetctState) {

this.subjetctState = subjetctState;

}

}



import java.util.ArrayList;

import java.util.List;
/**


@Author: cxh


@CreateTime: 18/1/10 09:11


@ProjectName: JavaBaseTest

*/

public class Boss extends Subject{

private List list=new ArrayList<>();
//增加观察者

public void add(Observer observer){

list.add(observer);

}

//删除观察者

public void delete(Observer observer){

list.remove(observer);

}

//通知

public void notifyObservers(){

for(Observer s:list)

s.update();

}

}



/**

@Author: cxh
@CreateTime: 18/1/9 23:17
@ProjectName: JavaBaseTest

*/

public interface Observer {

void update();

}



/**


@Author: cxh


@CreateTime: 18/1/9 23:28


@ProjectName: JavaBaseTest

*/

public class NBAObserver implements Observer {

private Subject subject;//关注主题

private String name;//观察者名字

public NBAObserver(String name,Subject subject){//参数Subject体现了:具体依赖抽象原则

this.name=name;

this.subject=subject;

}
@Override

public void update() {

System.out.println(subject.getSubjetctState()+","+name+","+"快继续工作~");

}

}



/**


@Author: cxh


@CreateTime: 18/1/9 23:45


@ProjectName: JavaBaseTest

*/

public class TVObserver implements Observer {

private String name;//看电视的人名字

private Boss subject;//主题

public TVObserver(String name,Boss subject){

this.name=name;

this.subject=subject;

}
@Override

public void update() {

System.out.println(subject.getSubjetctState()+","+"快继续工作~");

}

}

输出：

Process finished with exit code 0

import java.util.Date;
/**


@Author: cxh


@CreateTime: 18/1/12 16:40


@ProjectName: JavaBaseTest

*/

public class Client {

public static void main(String[] args) {

//观察者.  创建时起,开始做自己的事情

NBAObserver nbaObserver=new NBAObserver();

TVObserver tvObserver=new TVObserver();

//主题(通知者)

NotifierA notifierA=new NotifierA();
 //为主题添加观察者
 notifierA.addListener(nbaObserver,"stopWatchingNBA",new Date());
 notifierA.addListener(tvObserver,"stopWatchingTV",new Date());

 //主题状态改变,通知观察者
 notifierA.notifyX();
}

}



import java.lang.reflect.Method;
/**


@Author: cxh


@CreateTime: 18/1/10 23:29


@ProjectName: JavaBaseTest

*/

public class Event{

//要执行方法的对象

private Object object;

//要执行的方法名称

private String methodName;

//要执行方法的参数

private Object[] params;

//要执行方法的参数类型

private Class[] paramType;
//两个构造函数

public Event(){}

public Event(Object object,String methodName,Object... args){

this.object=object;

this.methodName=methodName;

this.params=args;

//获取参数类型

getParaTypes(args);

}

private void getParaTypes(Object[] params){

int size=params.length;

this.paramType=new Class[size];//4个私有变量,只有这个变量实现了深拷贝

for(int i=0;i<size;i++)

paramType[i]=params[i].getClass();

}
//执行该对象的方法

public void invoke() throws Exception{

Method method=object.getClass().getMethod(getMethodName(),getParamType());

if(null==method)

return;

method.invoke(getObject(),getParams());

}
//get,set方法

public Object getObject() {

return object;

}
public void setObject(Object object) {

this.object = object;

}
public String getMethodName() {

return methodName;

}
public void setMethodName(String methodName) {

this.methodName = methodName;

}
public Object[] getParams() {

return params;

}
public void setParams(Object[] params) {

this.params = params;

}
public Class[] getParamType() {

return paramType;

}
public void setParamType(Class[] paramType) {

this.paramType = paramType;

}

}



import java.util.ArrayList;

import java.util.List;
/**


@Author: cxh


@CreateTime: 18/1/12 11:23


@ProjectName: JavaBaseTest

*/

public class EventHandler {

//保存了很多event的引用

private List objects;

public EventHandler(){

objects=new ArrayList<>();

}
//添加某个event

public void addEvent(Object object,String name,Object... args){

objects.add(new Event(object,name,args));

}

//触发所有引用的event

public void notifyEvents() throws Exception{

for(Event e:objects)

e.invoke();

}

}



import java.util.Date;
/**

@Author: cxh
@CreateTime: 18/1/12 16:30
@ProjectName: JavaBaseTest

*/

public class NBAObserver{

public NBAObserver(){

System.out.println("正在观看NBA比赛!当前时间为:"+new Date());

}

public void stopWatchingNBA(Date date){

System.out.println("领导回来了,快关闭NBA赛事直播!当前时间为:"+date);

}

}



import java.util.Date;
/**

@Author: cxh
@CreateTime: 18/1/12 16:37
@ProjectName: JavaBaseTest

*/

public class TVObserver {

public TVObserver(){

System.out.println("正在观看电视剧<<甄嬛传>>,当前时间为:"+new Date());

}

public void stopWatchingTV(Date date){

System.out.println("领导回来了,快关闭电视剧播放.当前时间为:"+date);

}

}



/**


@Author: cxh


@CreateTime: 18/1/12 11:36


@ProjectName: JavaBaseTest

*/

public abstract class Notifier {

private EventHandler eventHandler=new EventHandler();

//增加需要帮忙放哨的同事

public abstract void addListener(Object object,Object... args);

//告诉所有需要帮忙放哨的同事:领导回来啦

public abstract void notifyX();
//get,set

public EventHandler getEventHandler() {

return eventHandler;

}
public void setEventHandler(EventHandler eventHandler) {

this.eventHandler = eventHandler;

}

}



/**


@Author: cxh


@CreateTime: 18/1/12 16:13


@ProjectName: JavaBaseTest

*/

public class NotifierA extends Notifier{
@Override

public void addListener(Object object,Object... args) {

getEventHandler().addEvent(object,args);

}
@Override

public void notifyX(){

try{

getEventHandler().notifyEvents();

}catch (Exception e){

System.out.println("通知同事时出错!!!");

}

}

}

（编辑：李大同）

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