观察者模式Observer和Observable的使用

Obersver 是 一个接口类代表观察者，继承实现它的update（Observable arg0, Object arg1）方法就可以定义一个具体的观察者类。

Observable是一个抽象类，继承后成为一个被观察的类，通过addOberser(Observer o)注册观察者。

当Observable的对象发生改变时先调用setChanged（）方法表示对象已改变,然后调用

notifyObserver(Obiect obj)

的方法通知观察者，并表示改变已完成。观察者受到通知后调用update（Observable arg0, Object arg1）方法

下面是用观察这模式模拟商品信息改变后通知商品显示界面的改变

//Action类定义了商品改变的细节状态

package wu.com.observer;

public final class Action {

public static final int PRODUCE_NAME_CHANGED=0;
public static final int PRODUCE_PRICE_CHANGED=1;
public static final int PRODUCE_COUNT_CHANGED=2;
}

//produce商品类继承Observable表示该类对象为被观察者

package wu.com.observer;

import java.util.Observable;

public class Produce extends Observable{

private String name;
private float price;
private int count;
public String getName() {
return name;
}

public void setName(String name) {
this.name = name;
setChanged();
notifyObservers(Action.PRODUCE_NAME_CHANGED);
}

public float getPrice() {
return price;
}

public void setPrice(float price) {
this.price = price;

//设置改变点
setChanged();

//通知观察者
notifyObservers(Action.PRODUCE_PRICE_CHANGED);
}

@Override
public String toString() {
return "Produce [name=" + name + ", price=" + price + ", count="
+ count + "]";
}

public int getCount() {
return count;
}

public void setCount(int count) {
this.count = count;
setChanged();
notifyObservers(Action.PRODUCE_COUNT_CHANGED);
}

}

//NameObserver产品名称改变监听类

package wu.com.observer;

import java.util.Observable;
import java.util.Observer;

public class NameObserver implements Observer{

@Override
public void update(Observable arg0, Object arg1) {
// TODO Auto-generated method stub
if (arg1.equals(Action.PRODUCE_NAME_CHANGED)) {
System.out.println("产平名称更新");
}
}

}

//产品价格改变监听类

package wu.com.observer;

import java.util.Observable;
import java.util.Observer;

public class PriceObserver implements Observer{

@Override
public void update(Observable arg0, Object arg1) {
// TODO Auto-generated method stub
if (arg1.equals(Action.PRODUCE_PRICE_CHANGED)) {
System.out.println("产平价格更新");
}
}

}

//用来模拟显示produce信息的Jlarble也实现监听者接口

package wu.com.observer;

import java.util.Observable;
import java.util.Observer;

import javax.swing.JLabel;

public abstract class MyJLarble extends JLabel implements Observer {

@Override
public abstract void update(Observable o, Object arg) ;

}

//测试类

package wu.com.observer;

import java.util.Observable;

import javax.swing.JFrame;

public class Test {

public static void main(String[] args) throws InterruptedException {
final Produce p=new Produce();
JFrame frame=new JFrame("产品");
frame.setBounds(400, 300, 300, 400);
MyJLarble lbPrice=new MyJLarble(){
@Override
public void update(Observable observer,Object obj){
if (obj.equals(Action.PRODUCE_PRICE_CHANGED)) {
setText(String.valueOf(p.getPrice()));
}
}
};
lbPrice.setBounds(0, 150, 300, 150);
MyJLarble lbNmae=new MyJLarble(){
@Override
public void update(Observable observer,Object obj){
if (obj.equals(Action.PRODUCE_NAME_CHANGED)) {
setText(p.getName());
}
}
};
lbNmae.setBounds(0, 0, 300, 150);
frame.add(lbNmae);
frame.add(lbPrice);
frame.setVisible(true);
NameObserver nameObserver=new NameObserver();
PriceObserver priceObserver=new PriceObserver();

p.addObserver(priceObserver);
p.addObserver(nameObserver);
p.addObserver(lbPrice);
p.addObserver(lbNmae);
p.setName("haha");
p.setPrice(8.20f);
System.out.println(p);
Thread.sleep(5000);

p.setName("嘿！您好！");
p.setPrice(10.20f);
System.out.println(p);
}
}