Nearby Messages using an IntentService

Question

Initially I setup a BroadcastReceiver to receive intents from the Nearby Messages API.

class BeaconMessageReceiver : BroadcastReceiver() {

    override fun onReceive(context: Context, intent: Intent) {
        Nearby.getMessagesClient(context).handleIntent(intent, object : MessageListener() {
            override fun onFound(message: Message) {
                val id = IBeaconId.from(message)
                Timber.i("Found iBeacon=$id")
                sendNotification(context, "Found iBeacon=$id")
            }

            override fun onLost(message: Message) {
                val id = IBeaconId.from(message)
                Timber.i("Lost iBeacon=$id")
                sendNotification(context, "Lost iBeacon=$id")
            }
        })
    }

    private fun sendNotification(context: Context, text: String) {
        Timber.d("Send notification.")
        val manager = context.getSystemService(Context.NOTIFICATION_SERVICE) as NotificationManager

        val notification = NotificationCompat.Builder(context, Notifications.CHANNEL_GENERAL)
                .setContentTitle("Beacons")
                .setContentText(text)
                .setSmallIcon(R.drawable.ic_notification_white)
                .build()

        manager.notify(NotificationIdGenerator.nextID(), notification)
    }

}

Then registered this receiver in my MainActivity after location permissions have been granted.

class MainActivity : AppCompatActivity() {

    // ...

    private fun onLocationPermissionsGranted() {
        val filter = MessageFilter.Builder()
                .includeIBeaconIds(UUID.fromString("B9407F30-F5F8-466E-AFF9-25556B57FEED"), null, null)
                .build()

        val options = SubscribeOptions.Builder().setStrategy(Strategy.BLE_ONLY).setFilter(filter).build()

        Nearby.getMessagesClient(context).subscribe(getPendingIntent(), options)
    }

    private fun getPendingIntent(): PendingIntent = PendingIntent.getBroadcast(
            this, 0, Intent(context, BeaconMessageReceiver::class.java), PendingIntent.FLAG_UPDATE_CURRENT)

}

This worked well while the app was open, but does not work when the app is closed. So I found this example, that demonstrates how to setup an IntentService to receive messages while the app is in the background.

The example does use the Nearby.Messages class, which was deprecated in favor of the MessagesClient. So I replaced the deprecated code with the MessagesClient implementation.

class MainActivity : AppCompatActivity() {

    // ...

    private fun onLocationPermissionsGranted() {
        val filter = MessageFilter.Builder()
                .includeIBeaconIds(UUID.fromString("B9407F30-F5F8-466E-AFF9-25556B57FEED"), null, null)
                .build()

        val options = SubscribeOptions.Builder().setStrategy(Strategy.BLE_ONLY).setFilter(filter).build()

        Nearby.getMessagesClient(context).subscribe(getPendingIntent(), options)
            .addOnSuccessListener {
                Timber.i("Subscribed successfully.")
                startService(Intent(this, BeaconMessageIntentService::class.java))
            }.addOnFailureListener {
                Timber.e(exception, "Subscription failed.")
            }
    }

    private fun getPendingIntent(): PendingIntent = PendingIntent.getBroadcast(
            this, 0, Intent(context, BeaconMessageIntentService::class.java), PendingIntent.FLAG_UPDATE_CURRENT)

}

And this is the IntentService (which is almost identical to my BroadcastReceiver).

class BeaconMessageIntentService : IntentService("BeaconMessageIntentService") {

    override fun onHandleIntent(intent: Intent?) {
        intent?.let {
            Nearby.getMessagesClient(this)
                    .handleIntent(it, object : MessageListener() {
                        override fun onFound(message: Message) {
                            val id = IBeaconId.from(message)
                            Timber.i("Found iBeacon=$id")
                            sendNotification("Found iBeacon=$id")
                        }

                        override fun onLost(message: Message) {
                            val id = IBeaconId.from(message)
                            Timber.i("Lost iBeacon=$id")
                            sendNotification("Lost iBeacon=$id")
                        }
                    })
        }
    }

    private fun sendNotification(text: String) {
        Timber.d("Send notification.")
        val manager = getSystemService(Context.NOTIFICATION_SERVICE) as NotificationManager

        val notification = NotificationCompat.Builder(this, Notifications.CHANNEL_GENERAL)
                .setContentTitle("Beacons")
                .setContentText(text)
                .setSmallIcon(R.drawable.ic_notification_white)
                .build()

        manager.notify(NotificationIdGenerator.nextID(), notification)
    }

}

onHandleIntent is called, and the Intent is not null; yet for some reason onFound() and onLost() are never called. Why would this be the case?

score 2 · Answer 1 · answered Dec 17 '18 at 11:46

It's not really a solution but what I found is this (credit to this answer):
I've tried a few configurations including a BroadcastReceiver and adding a JobIntentService to run the code in the background, but every time I got this the onExpired callback which you can set to the SubscribeOptions:

options.setCallback(new SubscribeCallback() {
    @Override
    public void onExpired() {
        super.onExpired();
        Toast.makeText(context.get(), "No longer Subscribing!", Toast.LENGTH_SHORT).show();
    }
}

When the subscribe occurred in the background it was delayed, but it was still called.

Notes:
1. When I've tested with Strategy.BLE_ONLY I did not get the onFound callback.
2. From Google's documentation:

Background subscriptions consumes less power than foreground subscriptions, but have higher latency and lower reliability

When testing I found this "lower reliability" to be an understatement: onFound was rarely called and I never got the onLost.

score 0 · Answer 2 · answered Jun 15 '20 at 12:07

I know this is a late reply, but I had the same problem and found out by debugging that it is an issue related to this error: "Attempting to perform a high-power operation from a non-Activity Context". This can be solved when calling Nearby.getMessagesClient(this) by passing in an activity context instead of this.

In my case I added a class extending Application which helps in returning this context (the below is in java but should be translatable to kotlin easily)

public class MyApplication extends Application {
    private Activity currentActivity = null;

    public Activity getCurrentActivity(){
        return currentActivity;
    }
    public void setCurrentActivity(Activity mCurrentActivity){
        this.currentActivity = mCurrentActivity;
    }
}

And in my base activity, from which all activities extend, I set the current activity by calling ((MyApplication) this.getApplicationContext()).setCurrentActivity(this); in the constructor.

My service can then call getMessagesClient with the correct context like below:

final Activity context = ((MyApplication)getApplicationContext()).getCurrentActivity();
Nearby.getMessagesClient(context).[...]

Do not forget to register your Application class in the AndroidManifest:

<application
android:name="com.example.xxx.MyApplication"`

Nearby Messages using an IntentService

2 Answers2