Overwrite existing alarm

Question

I create an alaram in my app which is calling a BroadcastReceiver to setup notifications ever day with this code:

Intent intent = new Intent(Benachrichtigung.CUSTOM_INTENT);
PendingIntent pendingIntent  = PendingIntent.getBroadcast(this, 0, intent, PendingIntent.FLAG_CANCEL_CURRENT);

Calendar calendar = Calendar.getInstance();
calendar.set(Calendar.HOUR_OF_DAY, 8);
calendar.set(Calendar.MINUTE, 00);
calendar.set(Calendar.SECOND, 00);

alram = (AlarmManager) getSystemService(Context.ALARM_SERVICE);
alram.setRepeating(AlarmManager.RTC_WAKEUP, calendar.getTimeInMillis(), (24 * 60 * 60 * 1000), pendingIntent);

Now I want that the user can set the time for the norification so I have to call calendar.set with the new value. How can I overwrite the existing alarm with a new one?

Answer 1

To cancel or update an alarm using AlarmManager the Intent must match using the filterEquals. So basically, you re-create the PendingIntent the same as you did for the original and AlarmManager will see that they are the same. This includes the REQUEST_CODE, INTENT_ACTION, and INTENT_DATA (I may be missing something there but those are important.

Note:

EXTRAS are not used in comparing the two Intents.

So if the two Intents are equal then the first will be overwritten. When I have more time I can try and find a resource to better explain that.

According to the Intent Docs filterEquals

Determine if two intents are the same for the purposes of intent resolution (filtering). That is, if their action, data, type, class, and categories are the same. This does not compare any extra data included in the intents.