Scheduling notifications

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Sometimes it is required to display a notification at a specific time, a task that unfortunately is not trivial on the Android system, as there is no method setTime() or similiar for notifications. This example outlines the steps needed to schedule notifications using the AlarmManager:

Add a BroadcastReceiver that listens to Intents broadcasted by the Android AlarmManager.

This is the place where you build your notification based on the extras provided with the Intent:

public class NotificationReceiver extends BroadcastReceiver {
    @Override
    public void onReceive(Context context, Intent intent) {
        // Build notification based on Intent
        Notification notification = new NotificationCompat.Builder(context)
            .setSmallIcon(R.drawable.ic_notification_small_icon)
            .setContentTitle(intent.getStringExtra("title", ""))
            .setContentText(intent.getStringExtra("text", ""))
            .build();
        // Show notification
        NotificationManager manager = (NotificationManager) context.getSystemService(Context.NOTIFICATION_SERVICE);
        manager.notify(42, notification);
    }
}

Register the BroadcastReceiver in your AndroidManifest.xml file (otherwise the receiver won’t receive any Intents from the AlarmManager):

<receiver
    android:name=".NotificationReceiver"
    android:enabled="true" />

Schedule a notification by passing a PendingIntent for your BroadcastReceiver with the needed Intent extras to the system AlarmManager. Your BroadcastReceiver will receive the Intent once the given time has arrived and display the notification. The following method schedules a notification:

public static void scheduleNotification(Context context, long time, String title, String text) {
    Intent intent = new Intent(context, NotificationReceiver.class);
    intent.putExtra("title", title);
    intent.putExtra("text", text);
    PendingIntent pending = PendingIntent.getBroadcast(context, 42, intent, PendingIntent.FLAG_UPDATE_CURRENT);
    // Schdedule notification
    AlarmManager manager = (AlarmManager) context.getSystemService(Context.ALARM_SERVICE);
    manager.setExactAndAllowWhileIdle(AlarmManager.RTC_WAKEUP, time, pending);
}

*Please note that the `42` above needs to be unique for each scheduled notification, otherwise the `PendingIntent`s will replace each other causing undesired effects!*

Cancel a notification by rebuilding the associated PendingIntent and canceling it on the system AlarmManager. The following method cancels a notification:

public static void cancelNotification(Context context, String title, String text) {
    Intent intent = new Intent(context, NotificationReceiver.class);
    intent.putExtra("title", title);
    intent.putExtra("text", text);
    PendingIntent pending = PendingIntent.getBroadcast(context, 42, intent, PendingIntent.FLAG_UPDATE_CURRENT);
    // Cancel notification
    AlarmManager manager = (AlarmManager) context.getSystemService(Context.ALARM_SERVICE);
    manager.cancel(pending);
}

Note that the 42 above needs to match the number from step 3!

Found a mistake? Have a question or improvement idea? Let me know.

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