WhatsApp不完全依赖GCM m不知道它是否依赖于GCM）。如果您打开Android设备的设置并转到应用程序，然后运行服务（如果您使用的是不同于我使用的Android版本的2.3.6版本，菜单可能会有所不同），您会看到有一个WhatsApp服务在后台运行（假设您安装了WhatsApp）。如果您停止该服务，您将停止从WhatsApp接收消息，直到您再次启动该应用程序为止。

只要您不杀死，您的应用程序就可以接受GCM广播它明确。一旦你杀了它，它将不会收到任何广播，直到你下一次启动它（根据我读到的，自从Android 3.x以来就是这种情况）。但是，如果您将应用移至后台（例如启动其他应用或点击后退按钮，直至移至主屏幕或其他应用），则您的应用仍会收到来自GCM的消息。

Recently I implement the GCM on my app. I followed the tutorial code at this website

http://javapapers.com/android/google-cloud-messaging-gcm-for-android-and-push-notifications/

However, the behavior is quite strange , for example

If I kill the app, then when I send the notification, it will not show on the notification bar immediately , but only when the user open the app again, say, if I send two notification when I kill app, I receive two notification only when I open the app.

Is it the behavior of GCM? As I expect it should be something like the whatsapp (even I did not open app, the device should still receive the notification and display)

here is my code. Thanks for helping

GcmBroadcastReceiver

public class GcmBroadcastReceiver extends WakefulBroadcastReceiver {

    @Override
    public void onReceive(Context context, Intent intent) {
        ComponentName comp = new ComponentName(context.getPackageName(),
                GCMNotificationIntentService.class.getName());
        startWakefulService(context, (intent.setComponent(comp)));
        setResultCode(Activity.RESULT_OK);
    }
}

GCMNotificationIntentService

public class GCMNotificationIntentService extends IntentService {

    public static final int NOTIFICATION_ID = 1;
    private NotificationManager mNotificationManager;
    NotificationCompat.Builder builder;

    public GCMNotificationIntentService() {
        super("GcmIntentService");
    }

    public static final String TAG = "GCMNotificationIntentService";

    @Override
    protected void onHandleIntent(Intent intent) {
        Bundle extras = intent.getExtras();
        GoogleCloudMessaging gcm = GoogleCloudMessaging.getInstance(this);

        String messageType = gcm.getMessageType(intent);

        if (!extras.isEmpty()) {
            if (GoogleCloudMessaging.MESSAGE_TYPE_SEND_ERROR.equals(messageType)) {
                sendNotification("Send error: " + extras.toString());
            } else if (GoogleCloudMessaging.MESSAGE_TYPE_DELETED.equals(messageType)) {
                sendNotification("Deleted messages on server: " + extras.toString());
            } else if (GoogleCloudMessaging.MESSAGE_TYPE_MESSAGE.equals(messageType)) {

                for (int i = 0; i < 3; i++) {
                    Log.i(TAG, "Working... " + (i + 1) + "/5 @ " + SystemClock.elapsedRealtime());
                    try {
                        Thread.sleep(5000);
                    } catch (InterruptedException e) {
                    }
                }

                Log.i(TAG, "Completed work @ " + SystemClock.elapsedRealtime());
                sendNotification(getResources().getString(R.string.gcm_news_remind));
                Log.i(TAG, "Received: " + extras.toString());
            }
        }
        GcmBroadcastReceiver.completeWakefulIntent(intent);
    }

    private void sendNotification(String msg) {
        Log.d(TAG, "Preparing to send notification...: " + msg);
        mNotificationManager = (NotificationManager) this.getSystemService(Context.NOTIFICATION_SERVICE);

        PendingIntent contentIntent = PendingIntent.getActivity(this, 0, new Intent(this, SplashScreen.class), 0);

        NotificationCompat.Builder mBuilder = new NotificationCompat.Builder(
                this).setSmallIcon(R.drawable.ic_launcher)
                .setContentTitle(getResources().getString(R.string.app_name))
                .setStyle(new NotificationCompat.BigTextStyle().bigText(msg))
                .setContentText(msg);

        mBuilder.setContentIntent(contentIntent);
        mNotificationManager.notify(NOTIFICATION_ID, mBuilder.build());
        Log.d(TAG, "Notification sent successfully.");
    }
}

Manifest

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.oshpedia"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-permission android:name="android.permission.INTERNET" />
    <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
    <uses-permission android:name="android.permission.GET_ACCOUNTS" />
    <uses-permission android:name="android.permission.WAKE_LOCK" />
    <uses-permission android:name="com.example.oshpedia.permission.C2D_MESSAGE" />
    <uses-permission android:name="com.google.android.c2dm.permission.RECEIVE" />
    <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
    <uses-permission android:name="android.permission.VIBRATE" />

    <permission
        android:name="com.example.oshpedia.permission.C2D_MESSAGE"
        android:protectionLevel="signature" />

    <uses-sdk
        android:minSdkVersion="9"
        android:targetSdkVersion="19" />

    <application
        android:name=".Defination.MyApp"
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:largeHeap="true"
        android:theme="@style/AppTheme" >
        <activity
            android:name=".Activity.SplashScreen"
            android:label="@string/app_name"
            android:theme="@android:style/Theme.NoTitleBar.Fullscreen" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <activity
            android:name=".Activity.Main"
            android:screenOrientation="portrait"
            android:windowSoftInputMode="stateHidden|adjustPan" >
        </activity>
        <activity
            android:name=".Activity.AboutUs"
            android:screenOrientation="portrait" >
        </activity>
        <activity
            android:name=".Activity.AboutApp"
            android:screenOrientation="portrait" >
        </activity>
        <activity
            android:name=".Activity.Disclaimer"
            android:screenOrientation="portrait" >
        </activity>
        <activity
            android:name=".Activity.EnquiryForm"
            android:screenOrientation="portrait"
            android:windowSoftInputMode="stateHidden|adjustPan" >
        </activity>
        <activity
            android:name=".Activity.NewsDetail"
            android:screenOrientation="portrait" >
        </activity>
        <activity
            android:name=".Activity.EnquiryDetail"
            android:screenOrientation="portrait" >
        </activity>
        <activity
            android:name=".Activity.SearchResult"
            android:screenOrientation="portrait" >
        </activity>
        <activity
            android:name=".Activity.LawDetail"
            android:screenOrientation="portrait" >
        </activity>
        <activity
            android:name=".Activity.AdvanceSearch"
            android:screenOrientation="portrait" >
        </activity>
        <activity
            android:name=".Activity.VideoChannel"
            android:screenOrientation="portrait" >
        </activity>
        <activity android:name=".Activity.VideoViewer" >
        </activity>

        <receiver
            android:name=".GCM.GcmBroadcastReceiver"
            android:permission="com.google.android.c2dm.permission.SEND" >
            <intent-filter>
                <action android:name="com.google.android.c2dm.intent.RECEIVE" />
                <action android:name="com.google.android.c2dm.intent.REGISTRATION" />

                <category android:name="com.example.oshpedia" />
            </intent-filter>
        </receiver>

        <service android:name=".GCM.GCMNotificationIntentService" />
    </application>

</manifest>

WhatsApp doesn't rely entirely on GCM (I'm not sure if it relies on GCM at all). If you open your Android device's Settings and go to Applications and then Running services (the menus may be a little different if you are using a different Android version than I'm using, which is 2.3.6), you'll see there's a WhatsApp service running in the background (assuming you have WhatsApp installed). If you stop that service, you would stop receiving messages from WhatsApp until you launch that app again.

Your app can accept GCM broadcasts only as long as you don't kill it explicitly. Once you kill it, it won't receive any broadcasts until the next time you launch it (according to what I read, that has been the case since Android 3.x). If, however, you move your app to the background (for example by launching another app or hitting the back button until you move to the home screen or to another app), your app would still get messages from GCM.