android 源码设计模式之--观察者模式
观察者模式也叫订阅者模式
1模式定义：
定义对象间的一种一对多的依赖关系，当一个对象的状态发送改变时，所有依赖于它的对象都能得到通知并被自动更新，
在观察者模式中，发生改变的对象称为观察目标，而被通知的对象称为观察者，一个观察目标可以对应多个观察者
2应用场景
当一个对象的状态改变时，与它所有的关联对象都会更新它已存在自己内部的状态
3组成部分
观察者，我们称它为Observer，有时候我们也称它为订阅者，即Subscriber
被观察者，我们称它为Observable，即可以被观察的东西，有时候还会称之为主题，即Subject
4示例场景说明
情景1
有一种短信服务，比如天气预报服务，一旦你订阅该服务，你只需按月付费，付完费后，每天一旦有天气信息更新，它就会及时向你发送最新的天气信息。这样你需不时时刻刻关注天气变化，一但天气变化了你却能第一时间收到变化通知，
情景2
杂志的订阅，你只需向邮局订阅杂志，缴纳一定的费用，当有新的杂志时，邮局会自动将杂志送至你预留的地址。
5代码示例讲解
1【实体类】--被观察的内容
package com.san.javatest.observer;
public class ContentObject {
public String mManName = "aaa";
public int mManAge = 30;
public int mManMoney = 10000;
public ContentObject(String mManName, int mManAge, int mManMoney) {
super();
this.mManName = mManName;
this.mManAge = mManAge;
this.mManMoney = mManMoney;
}
public String getmManName() {
return mManName;
}
public void setmManName(String mManName) {
this.mManName = mManName;
}
public int getmManAge() {
return mManAge;
}
public void setmManAge(int mManAge) {
this.mManAge = mManAge;
}
public int getmManMoney() {
return mManMoney;
}
public void setmManMoney(int mManMoney) {
this.mManMoney = mManMoney;
}
@Override
public String toString() {
// TODO Auto-generated method stub
return "ContentObject {"+
"mManName ="+mManName+
" mManAge ="+mManAge+
" mManMoney ="+mManMoney+"}";
}
}2【被观察者】---管理观察者
package com.san.javatest.observer;
import java.util.ArrayList;
import java.util.List;
/**
* 被观察者:Observable
* 即主题: Subject
* @author User
* @param <T>
*
*/
public class Observable<T> {
private List<Observer<T>> mListObserver = new ArrayList<Observer<T>>();
public void registerObserverable(Observer<T> mObserver){
if(mListObserver != null){
if(!mListObserver.contains(mObserver)){
mListObserver.add(mObserver);
}
}
}
public void unRegisterObserverable(Observer<T> mObserver){
if(mListObserver != null){
mListObserver.remove(mObserver);
}
}
public void notifyChange(T t){
for(Observer<T> mObserver: mListObserver){
mObserver.noChange(t);
}
}
public void clearAllObserable(){
if(mListObserver != null && mListObserver.size() != 0){
mListObserver.clear();
}
}
}3【观察者】 所有的观察者是它的派生类
package com.san.javatest.observer;
/*
* 观察者:Observer
* 即订阅者：Subscriber
*/
public interface Observer<T> {
public void noChange(T t);
}4【触发使用类】
package com.san.javatest.observer;
public class MianTest {
public static void main(String[] args) {
//观察者1
Observer<ContentObject> laowang = new Observer<ContentObject>(){
@Override
public void noChange(ContentObject mCObject) {
// TODO Auto-generated method stub
System.out.println(mCObject.toString());
}
};
//观察者2
Observer<ContentObject> laoliu = new Observer<ContentObject>(){
@Override
public void noChange(ContentObject mCObject) {
// TODO Auto-generated method stub
System.out.println(mCObject.toString());
}
};
//观察者3
Observer<ContentObject> laochen = new Observer<ContentObject>(){
@Override
public void noChange(ContentObject mCObject) {
// TODO Auto-generated method stub
System.out.println(mCObject.toString());
}
};
ContentObject aa = new ContentObject("laowang",19,222);
ContentObject bbb = new ContentObject("laoliu",29,8888);
Observable<ContentObject> server = new Observable<ContentObject>();
server.registerObserverable(laoliu);//注册观察者1
server.registerObserverable(laowang);//注册观察者2
server.registerObserverable(laochen);//注册观察者3
server.notifyChange(aa);//将实例体类aa的内容更新发送给所有注册者
System.out.println("----------------------");
server.notifyChange(bbb);//将实例体类bbb的内容更新发送给所有注册者
System.out.println("----------------------");
server.unRegisterObserverable(laowang);//观察者2取消观察
server.notifyChange(aa);
}
}示例代码输出：
ContentObject {mManName =laowang mManAge =19 mManMoney =222}
ContentObject {mManName =laowang mManAge =19 mManMoney =222}
ContentObject {mManName =laowang mManAge =19 mManMoney =222}
----------------------
ContentObject {mManName =laoliu mManAge =29 mManMoney =8888}
ContentObject {mManName =laoliu mManAge =29 mManMoney =8888}
ContentObject {mManName =laoliu mManAge =29 mManMoney =8888}
----------------------
ContentObject {mManName =laowang mManAge =19 mManMoney =222}
ContentObject {mManName =laowang mManAge =19 mManMoney =222}package com.san.javatest.observer;
public class ContentObjectNews {
public String mTitle;
public String mContent;
public String mAuthor;
public ContentObjectNews(String mTitle, String mContent, String mAuthor) {
super();
this.mTitle = mTitle;
this.mContent = mContent;
this.mAuthor = mAuthor;
}
@Override
public String toString() {
// TODO Auto-generated method stub
return "News{ title ="+mTitle+
"News Content ="+mContent+
"News author ="+mAuthor+"}";
}
}2【触发使用类】
package com.kte.javatest.observer;
public class MianTest {
public static void main(String[] args) {
//观察者1
Observer<ContentObjectMan> laowang = new Observer<ContentObjectMan>(){
@Override
public void noChange(ContentObjectMan mCObject) {
// TODO Auto-generated method stub
System.out.println(mCObject.toString());
}
};
//观察者2
Observer<ContentObjectMan> laoliu = new Observer<ContentObjectMan>(){
@Override
public void noChange(ContentObjectMan mCObject) {
// TODO Auto-generated method stub
System.out.println(mCObject.toString());
}
};
//观察者3
Observer<ContentObjectMan> laochen = new Observer<ContentObjectMan>(){
@Override
public void noChange(ContentObjectMan mCObject) {
// TODO Auto-generated method stub
System.out.println(mCObject.toString());
}
};
ContentObjectMan aa = new ContentObjectMan("laowang",19,222);
ContentObjectMan bbb = new ContentObjectMan("laoliu",29,8888);
Observable<ContentObjectMan> server = new Observable<ContentObjectMan>();
server.registerObserverable(laoliu);//注册观察者1
server.registerObserverable(laowang);//注册观察者2
server.registerObserverable(laochen);//注册观察者3
//server.notifyChange(aa);//将实例体类aa的内容更新发送给所有注册者
System.out.println("----------------------");
//server.notifyChange(bbb);//将实例体类bbb的内容更新发送给所有注册者
System.out.println("----------------------");
server.unRegisterObserverable(laowang);//观察者2取消观察
//server.notifyChange(aa);
/*---------------------------------------------------------------------------------------*/
Observer<ContentObjectNews> newObserver1 = new Observer<ContentObjectNews>(){
@Override
public void noChange(ContentObjectNews t) {
// TODO Auto-generated method stub
System.out.println(t);
}
};
Observer<ContentObjectNews> newObserver2 = new Observer<ContentObjectNews>(){
@Override
public void noChange(ContentObjectNews t) {
// TODO Auto-generated method stub
System.out.println(t);
}
};
ContentObjectNews news1 = new ContentObjectNews("news1","aaa","laowang");
ContentObjectNews news2 = new ContentObjectNews("news2","bbb","laoli");
Observable<ContentObjectNews> server2 = new Observable<ContentObjectNews>();
server2.registerObserverable(newObserver1);
server2.registerObserverable(newObserver2);
server2.notifyChange(news1);
server2.unRegisterObserverable(newObserver1);
server2.notifyChange(news2);
}
}示例输出结果
----------------------
----------------------
News{ title =news1News Content =aaaNews author =laowang}
News{ title =news1News Content =aaaNews author =laowang}
News{ title =news2News Content =bbbNews author =laoli}版权声明：如无特殊标注，文章均为本站原创，转载时请以链接形式注明文章出处。
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