Java监听器与观察者模式

观察者模式分为观察者（被通知并执行）和被观察者（添加观察者列表，事件触发通知）两部分，在java、.net等事件处理中使用广泛

观察者抽象类

public abstract class Observer {

public abstract void Update();
}

观察者A

public class ObserverA extends Observer {

@Override
public void Update() {
System.out.println("This is ObserverA Update");
}
}

观察者B

public class ObserverB extends Observer {

@Override
public void Update() {
System.out.println("This is ObserverB Update");
}
}

 

观察者C.......

 

被观察者

 

public class Observed {
List<Observer> list = new ArrayList<Observer>();
public void AddObserver(Observer o) {
list.add(o);
}

public void RemoveObserver(Observer o) {
list.remove(o);
}

public void Notify() {
for (Observer o : list) {
o.Update();
}
}
}

 

执行

 

public static void main(String[] args) {
Observed observed = new Observed();
observed.AddObserver(new ObserverA());
observed.AddObserver(new ObserverB());
observed.Notify();
}

 

观察者抽象类替换成观察者接口就是监听器了

public interface Observer {
public void Update();
}

 

public static void main(String[] args) {
Observed observed = new Observed();
observed.AddObserver(new Observer() {
@Override
public void Update() {
System.out.println("This is ObserverA Update");
}
});
observed.AddObserver(new Observer() {
@Override
public void Update() {
System.out.println("This is ObserverB Update");
}
});
observed.Notify();
}