FCM, GCM send data, mesasge, notification config, noti type head-up screen on etc.

https://stackoverflow.com/questions/37711082/how-to-handle-notification-when-app-in-background-in-firebase
1. Why is this happening?

There are two types of messages in FCM (Firebase Cloud Messaging):

Display Messages: These messages trigger the onMessageReceived() callback only when your app is in foreground
Data Messages: Theses messages trigger the onMessageReceived() callback even if your app is in foreground/background/killed
Firebase team have not developed a UI to send data-messages to your devices, yet.

https://stackoverflow.com/questions/3621599/wake-android-device-up
https://stackoverflow.com/questions/37570200/firebase-silent-apns-notification

https://github.com/phonegap/phonegap-plugin-push/blob/master/docs/PAYLOAD.md#push-message-arrives-with-app-in-background

With FCM, you can send two types of messages to clients:

Notification messages, sometimes thought of as "display messages."

Data messages, which are handled by the client app.

As per FCM official document

Use only data messages if you want to receive(In OnMessageReceived method) and process it when your app is in background.

Is this true ?

I have an app that should show headsup notification while the app is in both foreground and background(not in history).

In foreground case , i acheived this by the folowing method.

PendingIntent pendingIntent = PendingIntent.getActivity(ctx, 0, intent, PendingIntent.FLAG_UPDATE_CURRENT);
    NotificationCompat.Builder builder = new NotificationCompat.Builder(ctx);
    builder.setFullScreenIntent(pendingIntent,true);
But in background, it always showing in the notification area.Can anybody tell how to acheive this in background(not in history)

i tried the below parameters for notification but not working.

{ 
    "to" : "_Token_", 
    "priority":"high",
    "data":
    {
        "title": "Test",
        "text": "Fcm"
    },
    "notification":
    {
        "title": "Test",
        "text": "Fcm"
    }
}

Firebase allows notification customization when data messages are used. Data messages invokes onMessageReceived() method even when the app in backgroud so you create your custom notification.
The document says " When the app is in the background, Android directs notification messages to the system tray. A user tap on the notification opens the app launcher by default".


// From sample fcm
// [START_EXCLUDE]
// There are two types of messages data messages and notification messages. Data messages are handled
// here in onMessageReceived whether the app is in the foreground or background. Data messages are the type
// traditionally used with GCM. Notification messages are only received here in onMessageReceived when the app
// is in the foreground. When the app is in the background an automatically generated notification is displayed.
// When the user taps on the notification they are returned to the app. Messages containing both notification
// and data payloads are treated as notification messages. The Firebase console always sends notification
// messages. For more see: https://firebase.google.com/docs/cloud-messaging/concept-options
// [END_EXCLUDE]

public void onMessageReceived(RemoteMessage remoteMessage) {
...
// Also if you intend on generating your own notifications as a result of a received FCM

// message, here is where that should be initiated. See sendNotification method below.
...
}

Edit: for background you should do simillar. In order to show Heads-up notification there should be combination of high priority + sound and/or vibration (preferably both).
??

Messing between Server (service), API notification vs local (on device notification):
/**
     * Create and show a simple notification containing the received FCM message.
     *
     * @param messageBody FCM message body received.
     */
    private void sendNotification(String messageBody) {
    }


Ionic v1 plugins may be cause problem.
Push Plugin may be not trigger action when in background mode.
Background mode plugin (ver 0.7.2) need manually pull code from git to plugin dir not over cordova install.
Newer version (for native-ionic) is 4.1.0 may be not have this problems.