设计模式之观察者模式

设计模式之观察者模式

观察者模式的特点：定义了对象之间的一对多的依赖。

图什么的我就不太想画了。

简单说的是-找一个对象放置容器，容器放置实现某类接口的对象，当对象内容变化的时候同时调用容器里面对象对应的方法

大家可以理解为报纸订阅。报社和读者之间的对应关系

观察者模式的实现

当然你也可以使用实现
java.util.observable
java.util.observer;

package design_partner;

import java.util.ArrayList;
import java.util.Observer;

import org.omg.CORBA.PUBLIC_MEMBER;

public class TestObserver {

public static void main(String[] argv){

System.out.println("start:observer");
WeatherData weatherData = new WeatherData();
CurrentConditionDisplay conditionDisplay = new CurrentConditionDisplay(weatherData);
weatherData.setMeasurements(80, 65, 30.4f);
weatherData.setMeasurements(82, 70, 29.2f);
weatherData.setMeasurements(78, 90, 29.4f);

}
}

interface Subject{
public void registerObserver(MyObserver o);
public void removeObserver(MyObserver o);
public void notifyObservers();
}

interface MyObserver{
public void update(float temp,float humidity,float pressure);
}

interface DisplayElement{
public void display();
}

class WeatherData implements Subject{
private ArrayList<MyObserver> observers;
private float temperature;
private float humidity;
private float pressure;
public WeatherData() {
observers = new ArrayList<MyObserver>();
}

public void registerObserver(MyObserver o){
observers.add(o);
}
public void removeObserver(MyObserver o){
int i = observers.indexOf(o);
if(i>=0){
observers.remove(i);
}
}
public void notifyObservers(){
for(int i=0;i<observers.size();++i){
MyObserver observer = (MyObserver) observers.get(i);
observer.update(temperature, humidity, pressure);
}
}
public void measurementsChanged() {
notifyObservers();
}
public void setMeasurements(float temp,float humidity,float pressure) {
this.temperature = temp;
this.humidity = humidity;
this.pressure = pressure;
measurementsChanged();
}
}

class CurrentConditionDisplay implements MyObserver,DisplayElement{
private float temperature;
private float humidity;
private Subject weatherData;

CurrentConditionDisplay(Subject weatherData){
this.weatherData = weatherData;
weatherData.registerObserver(this);
}

public void update(float temperature,float humidity,float pressure){
this.temperature = temperature;
this.humidity = humidity;
display();
}

public void display(){
System.out.println("current conditions:"+temperature+"F degress and "+
humidity+" %humidity");
}

}