Android C2DM学习——云端推送

一．基础知识

当我们开发需要和服务器交互的应用程序时，基本上都需要获取服务器端的数据，比如《地震及时通》就需要及时获取服务器上最新的地震信息。要获取服务器上不定时更新的信息一般来说有两种方法，第一种是客户端使用Pull（拉）的方式，隔一段时间就去服务器上获取信息，看是否有更新的信息出现。第二种就是服务器使用Push（推送）的方式，当服务器端有新信息了，则把最新的信息Push到客户端上。
虽然Pull和Push两种方式都能实现获取服务器端更新信息的功能，但是明显来说Push is better than pull。因为Pull方式更费客户端的网络流量，更主要的是费电量。
Android从2.2版本开始增加了Cloud to Device Messaging（C2DM）框架，在系统中支持了Push功能，基于Android平台使用Push功能更加简单了。虽然C2DM目前还处在实验室阶段，不过小规模的使用应该没问题
下面我们就来体验一下Android的C2DM功能。

二．C2DM框架

使用Android的C2DM功能有几个要求：
1. 需要Android2.2及以上的系统版本。
2. 使用C2DM功能的Android设备上需要设置好Google的账户。
3. 需要在这里注册使用C2DM功能的用户邮箱账号（最好为C2DM单独注册一个Gmail邮箱账号）。
我们接下来C2DM的一个完整过程，这里借用一下Google官方推出的Chrome To Phone过程图来说明下。



图1 C2DM操作过程图
要使用C2DM来进行Push操作，基本上要使用以下6个步骤：
（1）注册：Android设备把使用C2DM功能的用户账户（比如android.c2dm.demo@gmail.com）和App名称发送给C2DM服务器。
（2）C2DM服务器会返回一个registration_id值给Android设备，设备需要保存这个registration_id值。
（3）Android设备把获得的registration_id和C2DM功能的用户账户（android.c2dm.demo@gmail.com）发送给自己的服务器，不过一般用户账户信息因为和服务器确定好的，所以不必发送。
这样Android设备就完成了C2DM功能的注册过程，接下来就可以接收C2DM服务器Push过来的消息了。
（4）服务器获得数据。这里图中的例子Chrome To Phone，服务器接收到Chrome浏览器发送的数据。数据也可以是服务器本地产生的。这里的服务器是Google AppEngine（很好的一项服务，可惜在国内被屏了），要换成自己的服务器。服务器还要获取注册使用C2DM功能的用户账户（android.c2dm.demo@gmail.com）的ClientLogin权限Auth。
（5）服务器把要发送的数据和registration_id一起，并且头部带上获取的Auth，使用POST的方式发送给C2DM服务器。
（6）C2DM服务器会以Push的方式把数据发送给对应的Android设备，Android设备只要在程序中按之前和服务器商量好的格式从对应的key中获取数据即可。
这样我们就大概明白了C2DM的工作流程，下面我们就结合一个实例来具体的说明以上6个步骤。

三．实例开发

我们要创建的程序名称为AndroidC2DMDemo，包名为com.ichliebephone.c2dm。
开始之前我们先去C2DM网页上注册一下使用C2DM功能的用户账户。



图2 应用程序名
其中应用程序名要填写带包名的完整名称，比如这里为om.ichliebephone.c2dm. AndroidC2DMDemo。



图3 C2DM用户账户注册
这里的contact邮箱使用一个你能接收到邮件的邮箱即可，下面的Role（sender）account邮箱最好单独注册一个Gmail邮箱来使用C2DM服务。我们这里使用的是专门注册的android.c2dm.deno@gmail.com邮箱。
提交后，过一段时间就会收到Google发送过来的确认邮件，然后你就可以使用C2DM的Push服务了。

介绍了这么多，我们先来快速完成一个实例，只完成Android设备端的注册部分，不包含向服务器发送registration_id和服务器向C2DM服务器发送数据的具体代码，这部分只是用Ubuntu下的curl命令来模拟，主要是快速亲自体验一下Push的结果。
创建一个Android工程AndroidC2DMDemo，并且包含进Google的开源例子Chrome To Phone中的c2dm包com.google.android.c2dm，包中包含三个Java类，分别为：
第一个类为C2DMBaseReceiver：

[java]
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/*
* Copyright 2010 Google Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/

package com.google.android.c2dm;

import java.io.IOException;

import android.app.AlarmManager;
import android.app.IntentService;
import android.app.PendingIntent;
import android.content.Context;
import android.content.Intent;
import android.os.PowerManager;
import android.util.Log;

/**
* Base class for C2D message receiver. Includes constants for the
* strings used in the protocol.
*/
/**
* 接收和处理C2DM消息的基类
* */
public abstract class C2DMBaseReceiver extends IntentService {
//和C2DM Push的Intent内容相关

//重新向C2DM服务器注册

private static final String C2DM_RETRY = "com.google.android.c2dm.intent.RETRY";
//向C2DM服务器注册后的回调处理

public static final String REGISTRATION_CALLBACK_INTENT = "com.google.android.c2dm.intent.REGISTRATION";
//接收到C2DM服务器的推送消息

private static final String C2DM_INTENT = "com.google.android.c2dm.intent.RECEIVE";

// Logging tag

private static final String TAG = "C2DM";

// Extras in the registration callback intents.

//向C2DM注册返回的intent中包含的key

public static final String EXTRA_UNREGISTERED = "unregistered";
public static final String EXTRA_ERROR = "error";
public static final String EXTRA_REGISTRATION_ID = "registration_id";
//向C2DM注册出错的原因

public static final String ERR_SERVICE_NOT_***AILABLE = "SERVICE_NOT_***AILABLE";
public static final String ERR_ACCOUNT_MISSING = "ACCOUNT_MISSING";
public static final String ERR_AUTHENTICATION_FAILED = "AUTHENTICATION_FAILED";
public static final String ERR_TOO_MANY_REGISTRATIONS = "TOO_MANY_REGISTRATIONS";
public static final String ERR_INVALID_PARAMETERS = "INVALID_PARAMETERS";
public static final String ERR_INVALID_SENDER = "INVALID_SENDER";
public static final String ERR_PHONE_REGISTRATION_ERROR = "PHONE_REGISTRATION_ERROR";

// wakelock

private static final String WAKELOCK_KEY = "C2DM_LIB";

private static PowerManager.WakeLock mWakeLock;
private final String senderId;

/**
* The C2DMReceiver class must create a no-arg constructor and pass the
* sender id to be used for registration.
*/
public C2DMBaseReceiver(String senderId) {
// senderId is used as base name for threads, etc.

super(senderId);
this.senderId = senderId;
}
//下面几个是接收到C2DM Push过来的信息后的回调函数，都可以在继承的子类中处理

/**
* Called when a cloud message has been received.
*/
/**
* 接收到C2DM服务器Push的消息后的回调函数，需要在继承的子类中处理
* */
protected abstract void onMessage(Context context, Intent intent);

/**
* Called on registration error. Override to provide better
* error messages.
*
* This is called in the context of a Service - no dialog or UI.
*/
/**
* 出错的回调函数
* */
public abstract void onError(Context context, String errorId);

/**
* Called when a registration token has been received.
*/
/**
* 注册后的回调函数
* */
public void onRegistered(Context context, String registrationId) throws IOException {
// registrationId will also be saved

}

/**
* Called when the device has been unregistered.
*/
/**
* 取消注册的回调函数
* */
public void onUnregistered(Context context) {
}

//IntentService的方法

@Override
public final void onHandleIntent(Intent intent) {
try {
Context context = getApplicationContext();
if (intent.getAction().equals(REGISTRATION_CALLBACK_INTENT)) {
handleRegistration(context, intent);//处理注册后的回调

} else if (intent.getAction().equals(C2DM_INTENT)) {
onMessage(context, intent);//处理C2DM Push消息的回调

} else if (intent.getAction().equals(C2DM_RETRY)) {
C2DMessaging.register(context, senderId); //重新注册

}
} finally {
// Release the power lock, so phone can get back to sleep.

// The lock is reference counted by default, so multiple

// messages are ok.


// If the onMessage() needs to spawn a thread or do something else,

// it should use it's own lock.

mWakeLock.release();
}
}


/**
* Called from the broadcast receiver.
* Will process the received intent, call handleMessage(), registered(), etc.
* in background threads, with a wake lock, while keeping the service
* alive.
*/
static void runIntentInService(Context context, Intent intent) {
if (mWakeLock == null) {
// This is called from BroadcastReceiver, there is no init.

PowerManager pm =
(PowerManager) context.getSystemService(Context.POWER_SERVICE);
mWakeLock = pm.newWakeLock(PowerManager.PARTIAL_WAKE_LOCK,
WAKELOCK_KEY);
}
mWakeLock.acquire();

// Use a naming convention, similar with how permissions and intents are

// used. Alternatives are introspection or an ugly use of statics.

String receiver = context.getPackageName() + ".C2DMReceiver";
intent.setClassName(context, receiver);

context.startService(intent);

}

//处理注册后的回调

private void handleRegistration(final Context context, Intent intent) {
final String registrationId = intent.getStringExtra(EXTRA_REGISTRATION_ID);
String error = intent.getStringExtra(EXTRA_ERROR);
String removed = intent.getStringExtra(EXTRA_UNREGISTERED);
Log.v(TAG, "handleRegistration");
//打印出接收到的registraton_id

Log.v(TAG, "dmControl: registrationId = " + registrationId +
", error = " + error + ", removed = " + removed);
if (Log.isLoggable(TAG, Log.DEBUG)) {
Log.d(TAG, "dmControl: registrationId = " + registrationId +
", error = " + error + ", removed = " + removed);
}
if (removed != null) {
// Remember we are unregistered

C2DMessaging.clearRegistrationId(context);
onUnregistered(context);
return;
} else if (error != null) {
// we are not registered, can try again

C2DMessaging.clearRegistrationId(context);
// Registration failed

Log.e(TAG, "Registration error " + error);
onError(context, error);
if ("SERVICE_NOT_***AILABLE".equals(error)) {
long backoffTimeMs = C2DMessaging.getBackoff(context);

Log.d(TAG, "Scheduling registration retry, backoff = " + backoffTimeMs);
Intent retryIntent = new Intent(C2DM_RETRY);
PendingIntent retryPIntent = PendingIntent.getBroadcast(context,
0 /*requestCode*/, retryIntent, 0 /*flags*/);

AlarmManager am = (AlarmManager) context.getSystemService(Context.ALARM_SERVICE);
am.set(AlarmManager.ELAPSED_REALTIME,
backoffTimeMs, retryPIntent);

// Next retry should wait longer.

backoffTimeMs *= 2;
C2DMessaging.setBackoff(context, backoffTimeMs);
}
} else {
try {
onRegistered(context, registrationId);
C2DMessaging.setRegistrationId(context, registrationId);
} catch (IOException ex) {
Log.e(TAG, "Registration error " + ex.getMessage());
}
}
}
}

[java] 
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/* 
 */  
package com.google.android.c2dm;  
  
import android.app.Activity;  
import android.content.BroadcastReceiver;  
import android.content.Context;  
import android.content.Intent;  
  
/** 
 * Helper class to handle BroadcastReciver behavior. 
 * - can only run for a limited amount of time - it must start a real service  
 * for longer activity 
 * - must get the power lock, must make sure it's released when all done. 
 *  
 */  
/** 
 * 帮助类，帮忙处理BroadcastReciver过程 
 * */  
public class C2DMBroadcastReceiver extends BroadcastReceiver {  
      
    @Override  
    public final void onReceive(Context context, Intent intent) {  
        // To keep things in one place.
  
        C2DMBaseReceiver.runIntentInService(context, intent);  
        setResult(Activity.RESULT_OK, null /* data */, null /* extra */);          
    }  
}  

/*
 */
package com.google.android.c2dm;

import android.app.Activity;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;

/**
 * Helper class to handle BroadcastReciver behavior.
 * - can only run for a limited amount of time - it must start a real service 
 * for longer activity
 * - must get the power lock, must make sure it's released when all done.
 * 
 */
/**
 * 帮助类，帮忙处理BroadcastReciver过程
 * */
public class C2DMBroadcastReceiver extends BroadcastReceiver {
    
    @Override
    public final void onReceive(Context context, Intent intent) {
        // To keep things in one place.
        C2DMBaseReceiver.runIntentInService(context, intent);
        setResult(Activity.RESULT_OK, null /* data */, null /* extra */);        
    }
}

第三个类为C2DMessaging：

[java]
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/*
* Copyright 2010 Google Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/

package com.google.android.c2dm;

import android.app.PendingIntent;
import android.content.Context;
import android.content.Intent;
import android.content.SharedPreferences;
import android.content.SharedPreferences.Editor;

/**
* Utilities for device registration.
*
* Will keep track of the registration token in a private preference.
*/
/**
* 和注册相关的一些实用函数
* */
public class C2DMessaging {
public static final String EXTRA_SENDER = "sender";
public static final String EXTRA_APPLICATION_PENDING_INTENT = "app";
public static final String REQUEST_UNREGISTRATION_INTENT = "com.google.android.c2dm.intent.UNREGISTER";
public static final String REQUEST_REGISTRATION_INTENT = "com.google.android.c2dm.intent.REGISTER";
public static final String LAST_REGISTRATION_CHANGE = "last_registration_change";
public static final String BACKOFF = "backoff";
public static final String GSF_PACKAGE = "com.google.android.gsf"; //GSF为GoogleServicesFramework.apk的缩写



// package

static final String PREFERENCE = "com.google.android.c2dm";

private static final long DEFAULT_BACKOFF = 30000;

/**
* Initiate c2d messaging registration for the current application
*/
public static void register(Context context,
String senderId) {
Intent registrationIntent = new Intent(REQUEST_REGISTRATION_INTENT);
registrationIntent.setPackage(GSF_PACKAGE);
registrationIntent.putExtra(EXTRA_APPLICATION_PENDING_INTENT,
PendingIntent.getBroadcast(context, 0, new Intent(), 0));
registrationIntent.putExtra(EXTRA_SENDER, senderId);
context.startService(registrationIntent);
// TODO: if intent not found, notification on need to have GSF

}

/**
* Unregister the application. New messages will be blocked by server.
*/
public static void unregister(Context context) {
Intent regIntent = new Intent(REQUEST_UNREGISTRATION_INTENT);
regIntent.setPackage(GSF_PACKAGE);
regIntent.putExtra(EXTRA_APPLICATION_PENDING_INTENT, PendingIntent.getBroadcast(context,
0, new Intent(), 0));
context.startService(regIntent);
}

/**
* Return the current registration id.
*
* If result is empty, the registration has failed.
*
* @return registration id, or empty string if the registration is not complete.
*/
public static String getRegistrationId(Context context) {
final SharedPreferences prefs = context.getSharedPreferences(
PREFERENCE,
Context.MODE_PRIVATE);
String registrationId = prefs.getString("dm_registration", "");
return registrationId;
}

public static long getLastRegistrationChange(Context context) {
final SharedPreferences prefs = context.getSharedPreferences(
PREFERENCE,
Context.MODE_PRIVATE);
return prefs.getLong(LAST_REGISTRATION_CHANGE, 0);
}

static long getBackoff(Context context) {
final SharedPreferences prefs = context.getSharedPreferences(
PREFERENCE,
Context.MODE_PRIVATE);
return prefs.getLong(BACKOFF, DEFAULT_BACKOFF);
}

static void setBackoff(Context context, long backoff) {
final SharedPreferences prefs = context.getSharedPreferences(
PREFERENCE,
Context.MODE_PRIVATE);
Editor editor = prefs.edit();
editor.putLong(BACKOFF, backoff);
editor.commit();

}

// package

static void clearRegistrationId(Context context) {
final SharedPreferences prefs = context.getSharedPreferences(
PREFERENCE,
Context.MODE_PRIVATE);
Editor editor = prefs.edit();
editor.putString("dm_registration", "");
editor.putLong(LAST_REGISTRATION_CHANGE, System.currentTimeMillis());
editor.commit();

}

// package

static void setRegistrationId(Context context, String registrationId) {
final SharedPreferences prefs = context.getSharedPreferences(
PREFERENCE,
Context.MODE_PRIVATE);
Editor editor = prefs.edit();
editor.putString("dm_registration", registrationId);
editor.commit();

}
}

[java] 
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package com.ichliebephone.c2dm;  
  
import com.google.android.c2dm.C2DMessaging;  
  
import android.app.Activity;  
import android.os.Bundle;  
import android.util.Log;  
  
public class AndroidC2DMDemo extends Activity {  
    /** Called when the activity is first created. */  
    private static final String TAG = "AndroidC2DMDemo";  
    public static final String SENDER_ID = "android.c2dm.demo@gmail.com"; //使用C2DM服务的用户账户
  
    public static final String MESSAGE_KEY_ONE = "msg";   //和服务器商量好的接收消息的键值key
  
      
    @Override  
    public void onCreate(Bundle savedInstanceState) {  
        super.onCreate(savedInstanceState);  
        setContentView(R.layout.main);  
          
        Log.v(TAG, "Start");  
        //向C2DM服务器注册
  
        C2DMessaging.register(this, SENDER_ID);  
    }  
      
      
}  

package com.ichliebephone.c2dm;

import com.google.android.c2dm.C2DMessaging;

import android.app.Activity;
import android.os.Bundle;
import android.util.Log;

public class AndroidC2DMDemo extends Activity {
    /** Called when the activity is first created. */
	private static final String TAG = "AndroidC2DMDemo";
	public static final String SENDER_ID = "android.c2dm.demo@gmail.com"; //使用C2DM服务的用户账户
	public static final String MESSAGE_KEY_ONE = "msg";   //和服务器商量好的接收消息的键值key
	
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        
        Log.v(TAG, "Start");
        //向C2DM服务器注册
        C2DMessaging.register(this, SENDER_ID);
    }
    
    
}

很简单，就是开始向C2DM服务器进行注册。
另一个类为C2DMBaseReceiver的子类C2DMReceiver：

[java]
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package com.ichliebephone.c2dm;

import java.io.IOException;

import android.app.Notification;
import android.app.NotificationManager;
import android.app.PendingIntent;
import android.content.Context;
import android.content.Intent;
import android.os.Bundle;
import android.util.Log;

import com.google.android.c2dm.C2DMBaseReceiver;
//接收C2DM服务器Push的消息，包括注册返回的registration_id消息，推送的数据消息等

public class C2DMReceiver extends C2DMBaseReceiver{

private static final String TAG="C2DMReceiver";
//

public C2DMReceiver()
{
super(AndroidC2DMDemo.SENDER_ID);
}
public C2DMReceiver(String senderId) {
super(senderId);
// TODO Auto-generated constructor stub

}
//接收到Push消息的回调函数

@Override
protected void onMessage(Context context, Intent intent) {
// TODO Auto-generated method stub

Log.v(TAG, "C2DMReceiver message");
Bundle extras = intent.getExtras();
if(extras!=null){
String msg = (String)extras.get(AndroidC2DMDemo.MESSAGE_KEY_ONE);
Log.v(TAG, "The received msg = "+msg);
//在标题栏上显示通知

NotificationManager notificationManager = (NotificationManager)getSystemService(NOTIFICATION_SERVICE);
Notification notification = new Notification(R.drawable.icon, msg, System.currentTimeMillis());
PendingIntent contentIntent = PendingIntent.getActivity(this, 0, new Intent(this, AndroidC2DMDemo.class), 0);
notification.setLatestEventInfo(this, getString(R.string.app_name), msg, contentIntent);
notificationManager.notify(0, notification);

}
}

@Override
public void onError(Context context, String errorId) {
// TODO Auto-generated method stub

Log.v(TAG, "C2DMReceiver error");
}

@Override
public void onRegistered(Context context, String registrationId)
throws IOException {
// TODO Auto-generated method stub

super.onRegistered(context, registrationId);
Log.v(TAG, "C2DMReceiver Register");
}
@Override
public void onUnregistered(Context context) {
// TODO Auto-generated method stub

super.onUnregistered(context);
Log.v(TAG, "C2DMReceiver UnRegister");
}
}

[html] 
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<?xml version="1.0" encoding="utf-8"?>  
<manifest xmlns:android="http://schemas.android.com/apk/res/android"  
      package="com.ichliebephone.c2dm"  
      android:versionCode="1"  
      android:versionName="1.0">  
    <uses-sdk android:minSdkVersion="8" />  
  
    <!--Only this application can receive the message and registration result  -->  
    <!-- 设置一个权限，使只有这个应用才能接收到对应Push的消息及注册时返回的结果  -->  
    <permission android:name="com.ichliebephone.c2dm.permission.C2D_MESSAGE"  
        android:protectionLevel="signature"></permission>  
    <uses-permission android:name="com.ichliebephone.c2dm.permission.C2D_MESSAGE"/>  
    <!-- This application has the permission to register and receive c2dm message -->  
    <!-- 设置注册和接收C2DM Push消息的权限 -->  
    <uses-permission android:name="com.google.android.c2dm.permission.RECEIVE" />  
    <!-- Send and registration id to the server  -->  
    <!-- 设置联网权限，在把registration_id发送给服务器的时候要用 -->  
    <uses-permission android:name="android.permission.INTERNET" />  
    <!-- App must have this permission to use the library -->  
    <!-- 其他和获取手机中用户账户相关的权限 -->  
    <uses-permission android:name="android.permission.WAKE_LOCK" />  
    <uses-permission android:name="android.permission.GET_ACCOUNTS" />  
    <uses-permission android:name="android.permission.USE_CREDENTIALS" />  
      
    <application android:icon="@drawable/icon" android:label="@string/app_name">  
        <activity android:name=".AndroidC2DMDemo"  
                  android:label="@string/app_name">  
            <intent-filter>  
                <action android:name="android.intent.action.MAIN" />  
                <category android:name="android.intent.category.LAUNCHER" />  
            </intent-filter>  
        </activity>  
          
        <!-- In order to use the c2dm library, an  
             application must declare a class with the name C2DMReceiver, in its   
             own package, extending com.google.android.c2dm.C2DMBaseReceiver                 
             It must also include this section in the manifest. -->  
        <!-- 为了使用c2dm包com.google.android.c2dm及其对应的3个类，我们需要声明一个  
            继承com.google.android.c2dm.C2DMBaseReceiver类的子类C2DMReceiver，  
            并且要在这声明下 -->       
        <service android:name=".C2DMReceiver" />  
                  
        <!-- Only google service can send data messages for the app. If permission is not set -  
             any other app can generate it -->   
        <!-- 谷歌的C2DM服务只为这个程序发送数据，声明对应的权限 -->  
        <receiver android:name="com.google.android.c2dm.C2DMBroadcastReceiver"  
                  android:permission="com.google.android.c2dm.permission.SEND">  
            <!-- Receive the actual message -->  
            <!-- 可以接收实际的Push数据 -->  
            <intent-filter>  
                <action android:name="com.google.android.c2dm.intent.RECEIVE" />  
                <category android:name="com.ichliebephone.c2dm" />  
            </intent-filter>  
            <!-- Receive the registration id -->  
            <!-- 可以接收注册后返回的registration_id -->  
            <intent-filter>  
                <action android:name="com.google.android.c2dm.intent.REGISTRATION" />  
                <category android:name="com.ichliebephone.c2dm" />  
            </intent-filter>  
        </receiver>  
    </application>  
</manifest>  

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
      package="com.ichliebephone.c2dm"
      android:versionCode="1"
      android:versionName="1.0">
    <uses-sdk android:minSdkVersion="8" />

	<!--Only this application can receive the message and registration result  -->
	<!-- 设置一个权限，使只有这个应用才能接收到对应Push的消息及注册时返回的结果  -->
	<permission android:name="com.ichliebephone.c2dm.permission.C2D_MESSAGE"
		android:protectionLevel="signature"></permission>
	<uses-permission android:name="com.ichliebephone.c2dm.permission.C2D_MESSAGE"/>
	<!-- This application has the permission to register and receive c2dm message -->
	<!-- 设置注册和接收C2DM Push消息的权限 -->
	<uses-permission android:name="com.google.android.c2dm.permission.RECEIVE" />
	<!-- Send and registration id to the server  -->
	<!-- 设置联网权限，在把registration_id发送给服务器的时候要用 -->
	<uses-permission android:name="android.permission.INTERNET" />
	<!-- App must have this permission to use the library -->
	<!-- 其他和获取手机中用户账户相关的权限 -->
    <uses-permission android:name="android.permission.WAKE_LOCK" />
    <uses-permission android:name="android.permission.GET_ACCOUNTS" />
    <uses-permission android:name="android.permission.USE_CREDENTIALS" />
    
    <application android:icon="@drawable/icon" android:label="@string/app_name">
        <activity android:name=".AndroidC2DMDemo"
                  android:label="@string/app_name">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
		
		<!-- In order to use the c2dm library, an
             application must declare a class with the name C2DMReceiver, in its 
             own package, extending com.google.android.c2dm.C2DMBaseReceiver               
             It must also include this section in the manifest. -->
        <!-- 为了使用c2dm包com.google.android.c2dm及其对应的3个类，我们需要声明一个
        	继承com.google.android.c2dm.C2DMBaseReceiver类的子类C2DMReceiver，
        	并且要在这声明下 -->     
        <service android:name=".C2DMReceiver" />
                
        <!-- Only google service can send data messages for the app. If permission is not set -
             any other app can generate it --> 
        <!-- 谷歌的C2DM服务只为这个程序发送数据，声明对应的权限 -->
        <receiver android:name="com.google.android.c2dm.C2DMBroadcastReceiver"
                  android:permission="com.google.android.c2dm.permission.SEND">
            <!-- Receive the actual message -->
            <!-- 可以接收实际的Push数据 -->
            <intent-filter>
                <action android:name="com.google.android.c2dm.intent.RECEIVE" />
                <category android:name="com.ichliebephone.c2dm" />
            </intent-filter>
            <!-- Receive the registration id -->
            <!-- 可以接收注册后返回的registration_id -->
            <intent-filter>
                <action android:name="com.google.android.c2dm.intent.REGISTRATION" />
                <category android:name="com.ichliebephone.c2dm" />
            </intent-filter>
        </receiver>
    </application>
</manifest>

因为C2DM功能只有2.2及以上的Android系统才支持，因此创建一个2.2及以上的***D，然后在”设置->账户与同步”里还要设置好Google Account，如下图所示：



图5 设置Android设备中的Google账户
然后就可以运行程序了，我们会在DDMS输出中看到获得的registration_id：



图6 获得的registration_id
如果第一次运行没有出现，试着再运行一次。
有了registration_id，我们的服务器端就可以向C2DM端发送需要Push的数据了，这里进行简单化处理下，在Ubuntu下直接使用curl命令来模拟服务器功能向C2DM发送数据。
我们先来获取C2DM的ClientLogin权限Auth，在Ubuntu终端下输入：

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lingaohe@lingaohe-laptop:~$ curl -d "accountType=HOSTED_OR_GOOGLE&Email=android.c2dm.demo@gmail.com&Passwd=androidc2dmdemo&service=ac2dm&source=bupt-c2dmdemo-1.0" https://www.google.com/accounts/ClientLogin

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SID=DQAAAKYAAADcTtHbBBNcZJEOfkfVRycD_ZOIidwsQ3UwIY7cSrYWaY6uhlfo0l9gRPB-mQxP4K2T5tWiG--vWVmSTeq5p8SPwgnsYvfzj7bkNiPPIy4xRimVVfBmAHnZgLohw7gHMKi5DS6kK-Ut5tNzdTkI0I2tUDF0ryQ7MnPpI6Sj-gUCyBXmvKatHHDnNTTV78XdGIx7FYej1DyqGsPsYo3bCstHgltjv3cd2Hs7D4yrpUWHZw  
LSID=DQAAAKgAAABCpaoUE4XvxM24Cofntw1IUGx5fKxX-m7aqTL0zhunP0OjzJ2sn9ywmPa1BMZ2cF2IchuxHFLVzaSQfydAmiHZJGXLgaUorpIN6yz1e0VFWKmS6j4wGjZOos3QoJ9rkha0jKbOiHfBesADjxk-qjJ24TJ0RL-xkZHQyzS69YlA1KyzqIKjAMCzgqaDfCwhqxylJzizJksO2h8xpAFXZ38d_grm8XYZtzejiCiAMAR65A  
Auth=DQAAAKoAAACRF4pgYULnXULoWgbwfdqmMiRhfZYa1l-LW_rwGD7cofov4L4c2bVrtCOXbEbkju_hhqdAonpMkrb5icptt28fU8c-s-u1y2MXNYDxPIdQzfA2t6oI3NTmyj35MpsR1NKL4TN7ZVEn6z9NueuiKAqLHukZYh1YMGkGC8M6rVvA7AWPW36064XCQED7KLVNp_pGT00lrni7UdZKZWEy0FT-EVR-OxDyHWw6C-5Kmfkisw  

SID=DQAAAKYAAADcTtHbBBNcZJEOfkfVRycD_ZOIidwsQ3UwIY7cSrYWaY6uhlfo0l9gRPB-mQxP4K2T5tWiG--vWVmSTeq5p8SPwgnsYvfzj7bkNiPPIy4xRimVVfBmAHnZgLohw7gHMKi5DS6kK-Ut5tNzdTkI0I2tUDF0ryQ7MnPpI6Sj-gUCyBXmvKatHHDnNTTV78XdGIx7FYej1DyqGsPsYo3bCstHgltjv3cd2Hs7D4yrpUWHZw
LSID=DQAAAKgAAABCpaoUE4XvxM24Cofntw1IUGx5fKxX-m7aqTL0zhunP0OjzJ2sn9ywmPa1BMZ2cF2IchuxHFLVzaSQfydAmiHZJGXLgaUorpIN6yz1e0VFWKmS6j4wGjZOos3QoJ9rkha0jKbOiHfBesADjxk-qjJ24TJ0RL-xkZHQyzS69YlA1KyzqIKjAMCzgqaDfCwhqxylJzizJksO2h8xpAFXZ38d_grm8XYZtzejiCiAMAR65A
Auth=DQAAAKoAAACRF4pgYULnXULoWgbwfdqmMiRhfZYa1l-LW_rwGD7cofov4L4c2bVrtCOXbEbkju_hhqdAonpMkrb5icptt28fU8c-s-u1y2MXNYDxPIdQzfA2t6oI3NTmyj35MpsR1NKL4TN7ZVEn6z9NueuiKAqLHukZYh1YMGkGC8M6rVvA7AWPW36064XCQED7KLVNp_pGT00lrni7UdZKZWEy0FT-EVR-OxDyHWw6C-5Kmfkisw

返回的内容包括SID，LSID和Auth三个部分，其中Auth是我们需要的内容。
有了Auth和registration_id值后，我们就可以继续用curl命令模拟我们自己服务器的功能向C2DM发送要推送的数据：

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lingaohe@lingaohe-laptop:~$ curl -H "Authorization:GoogleLogin auth=DQAAAKoAAACRF4pgYULnXULoWgbwfdqmMiRhfZYa1l-LW_rwGD7cofov4L4c2bVrtCOXbEbkju_hhqdAonpMkrb5icptt28fU8c-s-u1y2MXNYDxPIdQzfA2t6oI3NTmyj35MpsR1NKL4TN7ZVEn6z9NueuiKAqLHukZYh1YMGkGC8M6rVvA7AWPW36064XCQED7KLVNp_pGT00lrni7UdZKZWEy0FT-EVR-OxDyHWw6C-5Kmfkisw" -d "registration_id=APA91bGUBoSvt3G5Ny9t0IGLmIKAKYX6G6VHwSQHh3tP2fqcaQ0N4GPdKh5B3RDUHFCFF06YwT8ifOP_cOy5BAWyCLHL8d8NpuIW9AqXt9h2JSBVF2MitZA&collapse_key=1&data.msg=ichliebejiajia" https://android.apis.google.com/c2dm/send

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id=0:1308623423080544%6c5c15c200000031  
lingaohe@lingaohe-laptop:~$  

id=0:1308623423080544%6c5c15c200000031
lingaohe@lingaohe-laptop:~$

这时我们的服务器就已经把数据发送给C2DM服务器了，Android设备上一会就能接收到C2DM服务器Push的数据。

在我们的例子中我们可以看到DDMS中打印出的消息：



图7 获取到的Push数据
同时Android模拟器的状态栏上会有对应的通知显示：



图8 Android模拟器接收到的Push数据
这样我们就快速实现了下Android的C2DM框架的Push功能。进一步的具体解释说明及服务器端的代码处理我们以后再学习。


文章对应的完整代码例子下载地址：
http://download.csdn.net/source/3425855