[Android Q&A, Help & Troubleshooting] AlexAndro7385:
I decided to implement Google Cloud Messaging push notifications to notify users about news. I think it is topic messaging. For implement I took the Google GCM sample. I added all needed services, permissions and receiver in manifest. When I send a post request to Google GCM server, the response is true with message ID, but device doesn't notify. What is the matter? I tested in Bluestacks.

My manifest:

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="..."
xmlns:tools="..."
package="packagename" >

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

<permission android:name="packagename.permission.C2D_MESSAGE"
android:protectionLevel="signature" />

<application
android:name=".App"
android:allowBackup="true"
android:icon="@mipmap/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
<activity
android:name=".activities.MainActivity"
android:configChanges="keyboardHidden|orientation|screenSize"
android:label="@string/app_name"
android:launchMode="singleTop" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />

<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity
android:name=".activities.BiographyActivity"
android:configChanges="keyboardHidden|orientation|screenSize"
android:label="@string/title_biography"
android:parentActivityName=".activities.MainActivity"
tools:ignore="UnusedAttribute" >
<meta-data
android:name="android.support.PARENT_ACTIVITY"
android:value=".activities.MainActivity" />
</activity>
<activity
android:name=".activities.AboutActivity"
android:label="@string/title_about_app" >
<meta-data
android:name="android.support.PARENT_ACTIVITY"
android:value=".activities.MainActivity" />
</activity>
<activity android:name=".activities.CrashReportDialog"
android:theme="@style/Theme.Dialog"
android:process=":error_report"
android:launchMode="singleInstance"
android:excludeFromRecents="true"
android:finishOnTaskLaunch="true" />

<meta-data
android:name="com.google.android.gms.version"
android:value="@integer/google_play_services_version" />

<receiver
android:name="com.google.android.gms.gcm.GcmReceiver"
android:exported="true"
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="packagename" />
</intent-filter>
</receiver>
<service
android:name="packagename.AppGcmListenerService"
android:exported="false" >
<intent-filter>
<action android:name="com.google.android.c2dm.intent.RECEIVE" />
</intent-filter>
</service>
<service
android:name="packagename.AppInstanceIDListenerService"
android:exported="false">
<intent-filter>
<action android:name="com.google.android.gms.iid.InstanceID"/>
</intent-filter>
</service>
<service
android:name="packagename.RegistrationIntentService"
android:exported="false">
</service>
</application>

</manifest>

Main Activity:

public class MainActivity extends AppCompatActivity {

private BroadcastReceiver mRegistrationBroadcastReceiver;

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);

mRegistrationBroadcastReceiver = new BroadcastReceiver() {
@Override
public void onReceive(Context context, Intent intent) {
SharedPreferences sharedPreferences =
PreferenceManager.getDefaultSharedPreferences(context);
boolean sentToken = sharedPreferences
.getBoolean(GcmPreferences.SENT_TOKEN_TO_SERVER, false);
if (sentToken) {
Log.i("GCM", "Success!");
} else {
Log.i("GCM", "Error!");
}
}
};

Intent intent = new Intent(this, RegistrationIntentService.class);
startService(intent);
}
}

GCM Listener Service:

public class AppGcmListenerService extends GcmListenerService {

private static final String TAG = "GCM";

/**
* Called when message is received.
*
* @param from SenderID of the sender.
* @param data Data bundle containing message data as key/value pairs.
* For Set of keys use data.keySet().
*/
@Override
public void onMessageReceived(String from, Bundle data) {
String message = data.getString("message");
Log.d(TAG, "From: " + from);
Log.d(TAG, "Message: " + message);

/**
* Production applications would usually process the message here.
* Eg: - Syncing with server.
* - Store message in local database.
* - Update UI.
*/

/**
* In some cases it may be useful to show a notification indicating to the user
* that a message was received.
*/
sendNotification(message);
}

/**
* Create and show a simple notification containing the received GCM message.
*
* @param message GCM message received.
*/
private void sendNotification(String message) {
Intent intent = new Intent(this, MainActivity.class);
intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
PendingIntent pendingIntent = PendingIntent.getActivity(this, 0 /* Request code */, intent,
PendingIntent.FLAG_ONE_SHOT);

Uri defaultSoundUri= RingtoneManager.getDefaultUri(RingtoneManager.TYPE_NOTIFICATION);
NotificationCompat.Builder notificationBuilder = new NotificationCompat.Builder(this)
.setSmallIcon(R.drawable.ic_app)
.setContentTitle("GCM Message")
.setContentText(message)
.setAutoCancel(true)
.setSound(defaultSoundUri)
.setContentIntent(pendingIntent);

NotificationManager notificationManager =
(NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);

notificationManager.notify(0 /* ID of notification */, notificationBuilder.build());
}
}

Instance ID Listener Service:

public class AppInstanceIDListenerService extends InstanceIDListenerService {

/**
* Called if InstanceID token is updated. This may occur if the security of
* the previous token had been compromised. This call is initiated by the
* InstanceID provider.
*/
@Override
public void onTokenRefresh() {
// Fetch updated Instance ID token and notify our app's server of any changes (if applicable).
Intent intent = new Intent(this, RegistrationIntentService.class);
startService(intent);
}
}

Registration Intent Service:

public class RegistrationIntentService extends IntentService {

private static final String TAG = "GCM";

public RegistrationIntentService() {
super(TAG);
}

@Override
protected void onHandleIntent(Intent intent) {
SharedPreferences sharedPreferences = PreferenceManager.getDefaultSharedPreferences(this);

try {
// In the (unlikely) event that multiple refresh operations occur simultaneously,
// ensure that they are processed sequentially.
synchronized (TAG) {
// Initially this call goes out to the network to retrieve the token, subsequent calls
// are local.
InstanceID instanceID = InstanceID.getInstance(this);
String token = instanceID.getToken(getString(R.string.gcm_defaultSenderId),
GoogleCloudMessaging.INSTANCE_ID_SCOPE, null);

Log.d(TAG, "GCM Registration Token: " + token);

subscribeTopics(token);

// You should store a boolean that indicates whether the generated token has been
// sent to your server. If the boolean is false, send the token to your server,
// otherwise your server should have already received the token.
sharedPreferences.edit().putBoolean(GcmPreferences.SENT_TOKEN_TO_SERVER, true).apply();
}
} catch (Exception e) {
Log.d(TAG, "Failed to complete token refresh", e);
// If an exception happens while fetching the new token or updating our registration data
// on a third-party server, this ensures that we'll attempt the update at a later time.
sharedPreferences.edit().putBoolean(GcmPreferences.SENT_TOKEN_TO_SERVER, false).apply();
}
// Notify UI that registration has completed, so the progress indicator can be hidden.
Intent registrationComplete = new Intent(GcmPreferences.REGISTRATION_COMPLETE);
LocalBroadcastManager.getInstance(this).sendBroadcast(registrationComplete);
}

/**
* Subscribe to any GCM topics of interest, as defined by the TOPICS constant.
*
* @param token GCM token
* @throws IOException if unable to reach the GCM PubSub service
*/
private void subscribeTopics(String token) throws IOException {
GcmPubSub.getInstance(this).subscribe(token, "/topics/global", null);
}
}

My POST request:

GCM Server
Content-Type:application/json
Authorization:key=mykey

{
"to": "/topics/global",
"data": {
"message": "This is a GCM Topic Message!",
}
}

I tested POST request. Android app tested on Bluestacks App Player. I noticed also the app is not in the running services in the settings. Also I tested the app on real phone, but notifications still does not come :( I have no use for a long time working on it. The issue is strangely. I checked my code - whole is true as in the Google sample and documentation.