Android中的消息注冊Registrant機制

前面說過MessageHandle機制（見http://www.linuxidc.com/Linux/2011-10/45146.htm），它保證了Android上層代碼線程間的通信。

消息注冊機制更加豐富了MessageHandle的流程，它把過程嚴格階段化了，分成消息注冊和通知消息處理兩個部分，讓人一目了然。

消息注冊機制的總體思想是：一個對象中開辟一個空間用於存放Message，當調用regist方法時將Message存放進去，當其調用notify方法時將所有Message取出並發送到MessageQueue中等待處理。

下面是模擬程序，提供Registrant，RegistrantList，AsyncResult，MiddleUser類

package com.zte.liu.registermessage;

public class AsyncResult {

MessageParmeters parmList;
Object result;
Throwable exception;

public Throwable getException() {
return exception;
}

public void setException(Throwable exception) {
this.exception = exception;
}

AsyncResult(Object result, Throwable exception){
parmList = new MessageParmeters();
this.result = result;
this.exception = exception;
}

public MessageParmeters getMessageParms(){
return parmList;
}

public Object getResult(){
return result;
}

public void setResult(Object result){
this.result = result;
}

public AsyncResult refresh(Object parm){
parmList.refresh(parm);
return this;
}
}

package com.zte.liu.registermessage;

import com.zte.liu.messagehandler.Handler;

public class MiddleUser {

RegistrantList registrantList = new RegistrantList();

public void registForReason(Handler handler, int what, Object firstParms){
registrantList.add(handler, what, firstParms);
}

public void notifyRegistrant(Object secondParms, Throwable exception){
registrantList.notifyRegistrantList(secondParms, exception);
}

public void unRegistForReason(int what){
registrantList.remove(what);
}
}

package com.zte.liu.registermessage;

import com.zte.liu.messagehandler.Handler;
import com.zte.liu.messagehandler.Message;

public class Registrant {

private Message msg = null;

Registrant(Handler handler, int what, Object firstParms){
msg = new Message(what, handler, new AsyncResult(null, null).refresh(firstParms));
}

public void notifyRegistrant(Object secondParms, Throwable exception){
if(msg == null){
return;
}
AsyncResult asyncResult = (AsyncResult)msg.getObj();
asyncResult.refresh(secondParms).setException(exception);
msg.sendToTarget();
}

public Message getMessage(){
return msg;
}
}

package com.zte.liu.registermessage;

import java.util.ArrayList;

import com.zte.liu.messagehandler.Handler;

public class RegistrantList {

private ArrayList<Registrant> registrantList = new ArrayList<Registrant>();

public synchronized void add(Handler handler, int what, Object firstParms){
Registrant registrant = new Registrant(handler, what, firstParms);
registrantList.add(registrant);
}

public synchronized void remove(int what){
for(int i=0; i<registrantList.size(); i++){
if(((Registrant)registrantList.get(i)).getMessage().getId() == what){
registrantList.remove(i);
}
}
}

public synchronized void notifyRegistrantList(Object secondParms, Throwable exception){
for(int i=0; i<registrantList.size(); i++){
Registrant registrant = (Registrant)registrantList.get(i);
registrant.notifyRegistrant(secondParms, exception);
}
}

}