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观察者模式(一)
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1.觀察者定義了一種一對(duì)多依賴(lài)關(guān)系，讓多個(gè)觀察者同時(shí)監(jiān)聽(tīng)某個(gè)主題對(duì)象。這個(gè)主題對(duì)象在狀態(tài)上發(fā)生變化時(shí)，會(huì)通知所有的觀者對(duì)象，讓他們自動(dòng)更新自己。----這里的主題對(duì)象就是被觀察者
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2.代碼模擬
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?? 抽象主題角色AbstractWatched.java
???public interface AbstractWatched {
Java代碼? ?
????public?void?addWatcher(AbstractWatcher?watcher);?? ?????? ????public?void?removeWatcher(AbstractWatcher?watcher);?? ?????? ????public?void?removeAll();?? ?????? ????public?void?fire();?? }?? ?? ? ?具體主題角色ConcreteWatched.java
???public class ConcreteWatched implements AbstractWatched {
Java代碼? ?
private?List<AbstractWatcher>?watchers?=?new?ArrayList<AbstractWatcher>();?? ?? @Override?? public?void?addWatcher(AbstractWatcher?watcher)?{?? ????watchers.add(watcher);?? }?? ?? @Override?? public?void?removeAll()?{?? ????watchers.clear();?? }?? ?? @Override?? public?void?removeWatcher(AbstractWatcher?watcher)?{?? ????watchers.remove(watcher);?? }?? ?? @Override?? public?void?fire()?{?? ?????? ????for(AbstractWatcher?watcher?:?watchers){?? ????????watcher.update();?? ????}?? }?? ?
?? 抽象觀察者角色
???public interface AbstractWatcher {
Java代碼? ?
public?void?update();?? ??? ???
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?? 具體觀者角色
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Java代碼? ?
public?class?ConcreteWatcher?implements?AbstractWatcher?{?? ?? ????@Override?? ????public?void?update()?{?? ????????System.out.println("update.....");?? ????}?? ?? }?? ?
??測(cè)試代碼：
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Java代碼? ?
public?static?void?main(String[]?args)?{?? ????//被觀察者?? ????AbstractWatched?watched?=?new?ConcreteWatched();?? ?????? ????AbstractWatcher?watcher1?=?new?ConcreteWatcher();?? ????AbstractWatcher?watcher2?=?new?ConcreteWatcher();?? ????AbstractWatcher?watcher3?=?new?ConcreteWatcher();?? ?????? ????watched.addWatcher(watcher1);?? ????watched.addWatcher(watcher2);?? ????watched.addWatcher(watcher3);?? ?????? ????watched.fire();?? } ?
轉(zhuǎn)載于:https://my.oschina.net/wdkxyd/blog/160415
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