How to keep my Android app connected to the backend channel to receive updates and trigger events in device?

Question

I am working on an Android project where my app is connected to user_channel in background and shows a notification when a new event occurs in the channel.

The Viewmodel code

@RequiresApi(Build.VERSION_CODES.O)
fun getNotifications(callback: (Payload) -> Unit) {
    Coroutines.main {
        repository.receiveText { msg ->
            Log.d("NOTIFICATION", msg.toString())

            callback(msg)
        }
    }
}

The Repository code

suspend fun receiveText(callback: (Payload) -> Unit) {
    coroutineScope {
        async {
            sosChannel.on("notification") { message ->
                callback(message.payload)
            }
        }
    }
}

The Activity code

    viewModel.getNotifications() {
        runOnUiThread {
            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
                AlertNotification.alert(this, it["message"].toString() + "at " + it["latitude"] + " " + it["longitude"])
                v.vibrate(VibrationEffect.createOneShot(1500, VibrationEffect.DEFAULT_AMPLITUDE));
            } else {
                //deprecated in API 26
                v.vibrate(1500);
            }
            Toast.makeText(
                this,
                it["message"].toString() + "at " + it["latitude"] + " " + it["longitude"],
                Toast.LENGTH_LONG
            ).show()
        }
    }

Now when the app is in foreground, and my app is connected to channel , I can check for the event and it works fine But when the app is killed , the app leaves the channel an how can I keep connected to the channel to receive notification? I also learned that post Android Oreo background job is limited, despite Facebook and whatsapp like apps stay active in the backgrond ans show notifications, how do they do that - How can I proceed to achieve my goal , i.e. receiving notifications by staying connected to the channel in background an calling the Viewomdel method any suggestion is greatly appreciated , thanks in advance!

Answer 1

Facebook and whatsapp like apps stay active in the backgrond ans show notifications, how do they do that

The most appropriate way to show a notification even when the app is killed or in the background is to implement push notifications. This is typically how messaging apps alert about new messages.

That being said, push notifications need to be supported on both sides (your app and the back-end you're listening to). To support it on Android take a look at that https://firebase.google.com/docs/cloud-messaging

Otherwise, if you really wanna keep your app alive in the background and keep subscribing and running code (not good for battery and data usage) you will need to do that in a foreground service with a persistent notification for the user (not good for UX). I would advise avoiding this solution as much as possible. https://developer.android.com/guide/components/services