damonhuang

观察者模式:定义了对象之间的一对多依赖,这样一来,当一个对象改变状态时,它的所有依赖者都会收到通知并自动更新。 当你试图勾勒观察者模式时,可以利用报纸订阅服务,以及出版者和订阅者比拟这一切。

设计原则:为了交互对象之间的松耦合设计为努力。

工程名称:SubjectAndObsever(eclipse) 下载目录:http://www.cnblogs.com/jrsmith/admin/Files.aspx , SubjectAndObsever.zip

 1 package com.jyu.interfaces;
 2 
 3 /**
 4  * 主题接口
 5  * @author JRSmith
 6  *
 7  */
 8 public interface Subject {
 9 
10     /**注册观察者*/
11     public void registerObsever(Obsever obsever);
12     /**撤销观察者*/
13     public void removeObsever(Obsever obsever);
14     /**通知观察者*/
15     public void notifyObsever();
16 }
 1 package com.jyu.interfaces;
 2 
 3 /**
 4  * 观察者接口
 5  * @author JRSmith
 6  *
 7  */
 8 public interface Obsever {
 9     /**当气象观测值改变时,主题会把这些状态值当做方法的参数,传送给观察者*/
10     public void update(float temp,float humidity,float pressure);
11 }
 1 package com.jyu.interfaces;
 2 
 3 /**
 4  * 布告板接口
 5  * @author JRSmith
 6  *
 7  */
 8 public interface DisplayElement {
 9     /**当布告板需要显示时,调用此方法*/
10     public void display();
11 }
View Code
 1 package com.jyu.implement;
 2 
 3 import java.util.ArrayList;
 4 import java.util.List;
 5 
 6 import com.jyu.interfaces.Obsever;
 7 import com.jyu.interfaces.Subject;
 8 
 9 public class WeatherData implements Subject {
10 
11     private List<Obsever> obsevers;
12     private float temperature;
13     private float humidity;
14     private float pressure;
15     
16     public WeatherData(){
17         obsevers = new ArrayList<Obsever>();
18     }
19     
20     @Override
21     public void registerObsever(Obsever obsever) {
22         obsevers.add(obsever);
23     }
24 
25     @Override
26     public void removeObsever(Obsever obsever) {
27         int i = obsevers.indexOf(obsever);
28         if(i>=0){
29             obsevers.remove(i);
30         }
31     }
32 
33     @Override
34     public void notifyObsever() {
35         int size = obsevers.size();
36         for(int i = 0; i< size; i++){
37             Obsever obsever = obsevers.get(i);
38             obsever.update(temperature, humidity, pressure);
39         }
40     }
41 
42     /**
43      * 当从气象站得到更新观测值时,我们通知观测者
44      */
45     public void measurementsChanged(){
46         notifyObsever();
47     }
48     
49     public void setMeasurements(float temperature,float humidity,float pressure){
50         this.temperature = temperature;
51         this.humidity = humidity;
52         this.pressure = pressure;
53         measurementsChanged();
54     }
55 }
View Code
 1 package com.jyu.implement;
 2 
 3 import com.jyu.interfaces.DisplayElement;
 4 import com.jyu.interfaces.Obsever;
 5 import com.jyu.interfaces.Subject;
 6 
 7 public class CurrentConditionDisplay implements Obsever, DisplayElement {
 8 
 9     private float temperature;
10     private float humidity;
11     private Subject weatherData;
12     
13     /**构造器需要weatherData对象(也就是主题)作为注册之用*/
14     public CurrentConditionDisplay(Subject weatherData){
15         this.weatherData = weatherData;
16         weatherData.registerObsever(this);
17     }
18     
19 
20     @Override
21     public void update(float temp, float humidity, float pressure) {
22         this.temperature = temp;
23         this.humidity = humidity;
24         display();
25     }
26 
27     @Override
28     public void display() {
29         System.out.println("Currnet conditions:"+temperature+"F degree and "+humidity+"%humidity");
30     }
31 }
 1 package com.jyu.test;
 2 
 3 import com.jyu.implement.CurrentConditionDisplay;
 4 import com.jyu.implement.WeatherData;
 5 
 6 public class WeatherStation {
 7 
 8     /**
 9      * @param args
10      */
11     public static void main(String[] args) {
12         WeatherData weatherData = new WeatherData();
13         
14         CurrentConditionDisplay currentConditionDisplay = new CurrentConditionDisplay(weatherData);
15         
16         weatherData.setMeasurements(80, 65, 30.4f);
17     }
18 
19 }

 

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