Oreo - Foreground service does not show foreground notification

Code in kotlin

 private fun customNotification(title: String,notificationID: Int) {

                val intent = Intent(this, MainActivity::class.java)
                val pendingIntent = PendingIntent.getActivity(this, 0 /* request code */, intent, PendingIntent.FLAG_UPDATE_CURRENT)


                val builder = NotificationCompat.Builder(this, title)
                .setSound(RingtoneManager.getDefaultUri(RingtoneManager.TYPE_NOTIFICATION))
                .setContentText("Notification description")
                        .setSmallIcon(R.drawable.ic_mark_map)
                        .setContentIntent(pendingIntent)
                        .setOnlyAlertOnce(true)

                val mNotificationManager = getSystemService(Context.NOTIFICATION_SERVICE) as NotificationManager

                if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
                    val channel = NotificationChannel(title,
                            "Channel human readable title",
                            NotificationManager.IMPORTANCE_DEFAULT)
                    mNotificationManager.createNotificationChannel(channel)
                }

                 val notification = builder.build()
                 startForeground(notificationID, notification)
            }

Use:

 customNotification("Title",101)

You may need to define Notification Channel for your app. Check the log, there should be warning. Check this for introduction

I'll give you some example, it would be in kotin. First, make a class like this. You'll need to call createMainNotificationChannel() once at the start of your application.

class NotificationManager(private val context: Context) {

    companion object {
        private val CHANNEL_ID = "YOUR_CHANNEL_ID"
        private val CHANNEL_NAME = "Your human readable notification channel name"
        private val CHANNEL_DESCRIPTION = "description"
    }

    @RequiresApi(Build.VERSION_CODES.O)
    fun getMainNotificationId(): String {
        return CHANNEL_ID
    }

    @RequiresApi(Build.VERSION_CODES.O)
    fun createMainNotificationChannel() {
            val id = CHANNEL_ID
            val name = CHANNEL_NAME
            val description = CHANNEL_DESCRIPTION
            val importance = android.app.NotificationManager.IMPORTANCE_LOW
            val mChannel = NotificationChannel(id, name, importance)
            mChannel.description = description
            mChannel.enableLights(true)
            mChannel.lightColor = Color.RED
            mChannel.enableVibration(true)
            val mNotificationManager = context.getSystemService(Context.NOTIFICATION_SERVICE) as android.app.NotificationManager
            mNotificationManager.createNotificationChannel(mChannel)
    }
}

Then you can use util like this

fun createNotificationCompatBuilder(context: Context): NotificationCompat.Builder {
    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
        return NotificationCompat.Builder(context, NotificationManager(context).mainNotificationId)
    } else {
        return NotificationCompat.Builder(context)
    }
}