How to automatically send FCM message in flutter with firebase?

Question

I'm trying to send a notification automatically to driver with the following code:

static sendNotificationToDriver(String token, context, String ride_request_id) async
  {
    var destionation = Provider.of<AppData>(context, listen: false).dropOffLocation;
    print("this is the token: ");
    print(token);
    Map<String, String> headerMap =
    {
      'Content-Type': 'application/json',
      'Authorization': serverToken,
    };
    print(headerMap);
    Map notificationMap =
    {
      'body': 'DropOff Address, ${destionation!.placeName}',
      'title': 'New Ride Request'
    };
    print(notificationMap);
    Map dataMap =
    {
      'click_action': 'FLUTTER_NOTIFICATION_CLICK',
      'id': '1',
      'status': 'done',
      'ride_request_id': ride_request_id,
    };
    print(dataMap);
    Map sendNotificationMap =
    {
      "notification": notificationMap,
      "data": dataMap,
      "priority": "high",
      "to": token,
    };
    print(sendNotificationMap);
    var res = await http.post(
      Uri.parse('https://fcm.googleapis.com/fcm/send'),
      headers: headerMap,
      body: jsonEncode(sendNotificationMap),
    );
  }

However, the push notification doesn't go through.

But when I use postman with this code:

{"notification" : {"body" : "New Ride Request! Tap here to view in the app.", 
"title": "New Ride Request"}, "priority": "high", "data": {"click_action": "FLUTTER_NOTIFIATION_CLICK", 
"id": "1", "status": "done", "ride_request_id": "-MqrfzH5DKC8hTYQHy35"}, 
"to" : "dTlAVB_KTe-XZTLEYwZL10:APA91bF-D-Uh5Yb5p2uCwRr8oT90R_BXOw9qCUGMGsWqlp9RNc-WlyyNfJOKSwPArvAa3062F2XxlUJbY6xibWCYZCDPGqvaQG4xvfgByyyJ9SBxvhAgDmaP35Mqr3dfJADmprMQJ-aL"}

It works. I don't know which part I did wrong.

Here are the results of the print statements above:

I/flutter ( 1288): {Content-Type: application/json, Authorization: AAAAUecji90:APA***********************}
I/flutter ( 1288): {body: DropOff Address, ACE Centerpoint Gen. San. Drive Wing, title: New Ride Request}
I/flutter ( 1288): {click_action: FLUTTER_NOTIFICATION_CLICK, id: 1, status: done, ride_request_id: -MqrfCLsW3Ncmfav7hdk}
I/flutter ( 1288): {notification: {body: DropOff Address, ACE Centerpoint Gen. San. Drive Wing, title: New Ride Request}, data: {click_action: FLUTTER_NOTIFICATION_CLICK, id: 1, status: done, ride_request_id: -MqrfCLsW3Ncmfav7hdk}, priority: high, to: dTlAVB_KTe-XZTLEYwZL10:APA91bF-D-Uh5Yb5p2uCwRr8oT90R_BXOw9qCUGMGsWqlp9RNc-WlyyNfJOKSwPArvAa3062F2XxlUJbY6xibWCYZCDPGqvaQG4xvfgByyyJ9SBxvhAgDmaP35Mqr3dfJADmprMQJ-aL}

Answer 1

I finally managed to get it to work. I used the following codes:

 static sendNotificationToDriver(String token, context, String rideRequestId) async {
    if (token == null) {
      print('Unable to send FCM message, no token exists.');
      return;
    }

    try {
      await http.post(
        Uri.parse('https://fcm.googleapis.com/fcm/send'),
        headers: <String, String>{
          'Content-Type': 'application/json; charset=UTF-8',
          'Authorization': serverToken,
        },
        body: constructFCMPayload(token, rideRequestId),
      );
      print('FCM request for device sent!');
    } catch (e) {
      print(e);
    }
  }


static String constructFCMPayload(String token, String rideRequestId) {
  var res = jsonEncode({
    'token': token,
    'notification': {
      "body" : "You have a new ride request! Tap here to view in the app.",
      "title": "New Ride Request"
    },
    "priority": "high",
    'data': {
      "click_action": "FLUTTER_NOTIFIATION_CLICK",
      "id": "1",
      "status": "done",
      "ride_request_id": rideRequestId,
    },
    'to': token,

  });

  print(res.toString());
  return res;
}

However, the code wasn't the problem itself, but the serverToken variable. No wonder why it works using Postman and not in app because I forgot to put "key=" at the beginning of the serverToken value. Now, the problem is solved.