What's “requestCode” used for on PendingIntent

Question

Background:

I'm using PendingIntent for alarms via AlarmManager.

The problem:

At first I thought that in order to cancel previous ones, I must provide the exact requestCode that I've used before to start the alarm.

But then I've found out I was wrong, as the cancellation API says:

Remove any alarms with a matching Intent. Any alarm, of any type, whose Intent matches this one (as defined by filterEquals(Intent)), will be canceled.

looking at "filterEquals", the documentation says:

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.

so I don't get what the "requestCode" is for...

The question:

What is "requestCode" used for?

What if I create multiple alarms with the same "requestCode" ? do they override each other?

Answer 1

in my case i want to open the same activity with two different intents so if two or more FCMS are there in the tray, any one of them will only open other will not, so i changed the requests codes of pending intent then it worked.

 PendingIntent pendingIntent =
                            PendingIntent.getActivity(this, **Some unique id for all GCMS** /* Request code */, intent,
                                    PendingIntent.FLAG_ONE_SHOT);

Answer 2

1. requestCode is used to retrieve the same pending intent instance later on (for cancelling, etc).
2. Yes, my guess is the alarms will override each other. I would keep the request codes unique.

Answer 3

I just want to add to @Minhaj Arfin answer

1- requestCode is used to get the same pending intent later on (for cancelling etc)

2- Yes, they will get override as long as your specify the same Receiver to your Intent that you specify on your PendingIntent

example:

Intent startIntent1 = new Intent(context, AlarmReceiverFirst.class);
PendingIntent pendingIntent1 = PendingIntent.getBroadcast(context, 0, startIntent1, 0);

Intent startIntent2 = new Intent(context, AlarmReceiverSecond.class);
PendingIntent pendingIntent2 = PendingIntent.getBroadcast(context, 0, startIntent2, 0);

From above example, they will not override each other because the receiver is different(AlarmReceiverFirst and AlarmReceiverSecond)

Intent startIntent2 = new Intent(context, AlarmReceiverSecond.class);
PendingIntent pendingIntent2 = PendingIntent.getBroadcast(context, 0, startIntent2, 0);

Intent startIntent3 = new Intent(context, AlarmReceiverSecond.class);
PendingIntent pendingIntent3 = PendingIntent.getBroadcast(context, 0, startIntent3, 0);

From above example, they will override each other, because the receiver is same(AlarmReceiverSecond)