一、概述：
1、定義：觀察者模式定義了一種一對(duì)多的依賴關(guān)系，讓多個(gè)觀察者對(duì)象同時(shí)監(jiān)聽某一個(gè)主題對(duì)象。這個(gè)主題對(duì)象在狀態(tài)發(fā)生變化時(shí),會(huì)通知所有觀察者對(duì)象，使它們能夠自動(dòng)更新自己。
2、結(jié)構(gòu)圖：
public interface Subject {
void registerObserver(Observer observer);
void unregisterObserver(Observer observer);
void notifyObservers();
}public interface Observer {
void update();
}
實(shí)現(xiàn)文章來源：http://www.zghlxwxcb.cn/news/detail-676092.html
import java.util.ArrayList;
import java.util.List;
public class ConcreteSubject implements Subject {
private List<Observer> observers = new ArrayList<>();
private int state;
public int getState() {
return state;
}
public void setState(int state) {
this.state = state;
notifyObservers();
}
@Override
public void registerObserver(Observer observer) {
observers.add(observer);
}
@Override
public void unregisterObserver(Observer observer) {
observers.remove(observer);
}
@Override
public void notifyObservers() {
for (Observer observer : observers) {
observer.update();
}
}
}public class ConcreteObserver implements Observer {
private int observerState;
private ConcreteSubject subject;
public ConcreteObserver(ConcreteSubject subject) {
this.subject = subject;
this.subject.registerObserver(this);
}
@Override
public void update() {
observerState = subject.getState();
System.out.println("Observer state updated: " + observerState);
}
}?調(diào)用文章來源地址http://www.zghlxwxcb.cn/news/detail-676092.html
public class Main {
public static void main(String[] args) {
ConcreteSubject subject = new ConcreteSubject();
ConcreteObserver observer1 = new ConcreteObserver(subject);
ConcreteObserver observer2 = new ConcreteObserver(subject);
subject.setState(10);
// 輸出：
// Observer state updated: 10
// Observer state updated: 10
subject.setState(20);
// 輸出：
// Observer state updated: 20
// Observer state updated: 20
subject.unregisterObserver(observer2);
subject.setState(30);
// 輸出：
// Observer state updated: 30
}
}到了這里，關(guān)于設(shè)計(jì)模式（11）觀察者模式的文章就介紹完了。如果您還想了解更多內(nèi)容，請(qǐng)?jiān)谟疑辖撬阉鱐OY模板網(wǎng)以前的文章或繼續(xù)瀏覽下面的相關(guān)文章，希望大家以后多多支持TOY模板網(wǎng)！
