Flutter: How do I send a push notification from the device itself?

Question

I'm new to programming and I'm developing an app in which the user is suppose to get a notification 30 minutes before an event that's scheduled on the app. The schedule is saved in the firebase database and the device checks every 30 minutes to see if it's time to send an alert. If that condition becomes true, I want the device to send the notification so that the user will be alerted about the event. Every tutorial I saw only showed how to send notification through firebase itself. None of them covered how you can send them from the device.

I came across this code:

final postUrl = Uri.parse('https://fcm.googleapis.com/fcm/send');
    final data = {
      "registration_ids": tokens, //list of tokens
      "collapse_key": "type_a",
      "notification": {
        "title": 'title',
        "body": 'body',
      },
      "data": {
        "data1": 'data 1', //data passed
      }
    };

    final Map<String, String> headers = {
      'content-type': 'application/json',
      'Authorization': serverKey, //..................FCM server key
    };

    final response = await http.post(postUrl,
        body: json.encode(data),
        encoding: Encoding.getByName('utf-8'),
        headers: headers);

    if (response.statusCode == 200) {
      print('test ok push CFM');
      return true;
    } else {
      print(' CFM error');
      print(response.statusCode);
      return false;
    }
  }

But isn't this bad practice since your server key is exposed? Are there any better and safe methods to do this using flutter??

Answer 1

I think checking the firebase database every 30 minutes from the device is not a good decision.

You can use/write a firebase cloud function. Using a firebase cloud function you can watch any document/field and try to write notification trigger logic like if a event is before 30 minutes then this cloud function will throw a notification via firebase messaging.

See https://firebase.flutter.dev/docs/functions/overview/ for more information.