前台Service

private fun startForeground() {
    val channelId =
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
            createNotificationChannel("my_service", "My Background Service")
        } else {
            // If earlier version channel ID is not used
            // https://developer.android.com/reference/android/support/v4/app/NotificationCompat.Builder.html#NotificationCompat.Builder(android.content.Context)
            ""
        }

    val notificationBuilder = NotificationCompat.Builder(this, channelId )
    val notification = notificationBuilder.setOngoing(true)
        .setSmallIcon(R.mipmap.ic_launcher)
        .setPriority(PRIORITY_MIN)
        .setCategory(Notification.CATEGORY_SERVICE)
        .build()
    startForeground(101, notification)
}

@RequiresApi(Build.VERSION_CODES.O)
private fun createNotificationChannel(channelId: String, channelName: String): String{
    val chan = NotificationChannel(channelId,
        channelName, NotificationManager.IMPORTANCE_NONE)
    chan.lightColor = Color.BLUE
    chan.lockscreenVisibility = Notification.VISIBILITY_PRIVATE
    val service = getSystemService(Context.NOTIFICATION_SERVICE) as NotificationManager
    service.createNotificationChannel(chan)
    return channelId
}

override fun onCreate() {
    super.onCreate()
    startForeground()
}