Alarm Manager

Example of how to send a notification at a custom time via Alarm Manager

Permissions Required

<uses-permission android:name="android.permission.POST_NOTIFICATIONS" />
<uses-permission android:name="android.permission.SCHEDULE_EXACT_ALARM" />
<uses-permission android:name="android.permission.RECEIVE_BOOT_COMPLETED" />

⚠️ Remember to register the receiver in the manifest ℹ️ android.permission.RECEIVE_BOOT_COMPLETED is not necessary if you don’t activate the alarm when the device boots up

Create a BroadcastReceiver for pushing notification

class AlarmReceiver : BroadcastReceiver() {
    override fun onReceive(context: Context, intent: Intent) {
        sendNotification(context)
    }

    private fun sendNotification(context: Context) {
        val notificationManager =
        context.getSystemService(Context.NOTIFICATION_SERVICE) as NotificationManager
        val notificationId = (100..200).random()
        val channelId = "hello_background"

        val channel =
        NotificationChannel(
            channelId,
            "hello_background",
            NotificationManager.IMPORTANCE_HIGH
        )
        notificationManager.createNotificationChannel(channel)

        val notification = NotificationCompat.Builder(context, channelId)
            .setContentTitle("It's time to die")
            .setContentText("A test message!!!")
            .setSmallIcon(R.drawable.play)
            .build()

        notificationManager.notify(notificationId, notification)
    }
}

Set the alarm via AlarmManager

@SuppressLint("ScheduleExactAlarm")
fun setExactAlarm(context: Context, triggerTime: Long) {
    val alarmManager = context.getSystemService(Context.ALARM_SERVICE) as AlarmManager
    val intent = Intent(context, AlarmReceiver::class.java)
    val pendingIntent = PendingIntent.getBroadcast(
        context,
        0,
        intent,
        PendingIntent.FLAG_UPDATE_CURRENT or PendingIntent.FLAG_IMMUTABLE
    )

    alarmManager.setExactAndAllowWhileIdle(AlarmManager.RTC_WAKEUP, triggerTime, pendingIntent)
}