Update time for AlarmManager (Android)

Question

I use AlarmManager to display a notification for an event at the event date and time. But how can I update the time the AlarmManager sends the PendingIndent to my app, when an event is updated?

When an event is created the following code is called:

public void setOneTimeAlarm() {
        Intent intent = new Intent(this, TimerReceiver.class);
        PendingIntent pendingIntent = PendingIntent.getBroadcast(this, 0,
                intent, PendingIntent.FLAG_ONE_SHOT);

        Calendar c = Calendar.getInstance();
        c.set(Calendar.YEAR, year);
        c.set(Calendar.MONTH, month);
        c.set(Calendar.DAY_OF_MONTH, day-1);
        c.set(Calendar.HOUR_OF_DAY, 18);
        c.set(Calendar.MINUTE, 00);

        long date = c.getTimeInMillis();

        mAlarmManager.set(AlarmManager.RTC_WAKEUP, date, pendingIntent);
    }

The indent called is TimerReciver:

@Override
     public void onReceive(Context context, Intent intent) {
         Log.v("TimerReceiver", "onReceive called!");
         Intent notificationIntent = new Intent(context, ListTests.class);
            PendingIntent contentIntent = PendingIntent.getActivity(context,
                    123, notificationIntent,
                    PendingIntent.FLAG_CANCEL_CURRENT);

            NotificationManager nm = (NotificationManager) context.getSystemService(Context.NOTIFICATION_SERVICE);

            Resources res = context.getResources();
            NotificationCompat.Builder builder = new NotificationCompat.Builder(context);

            long[] pattern = {0,300};

            builder.setContentIntent(contentIntent)
                        .setSmallIcon(R.drawable.ic_launcher)
                        .setLargeIcon(BitmapFactory.decodeResource(res, R.drawable.ic_launcher))
                        .setTicker(res.getString(R.string.app_name))
                        .setWhen(System.currentTimeMillis())
                        .setAutoCancel(true)
                        .setVibrate(pattern)
                        .setContentTitle(res.getString(R.string.notification_title))
                        .setContentText(res.getString(R.string.notification_text));
            Notification n = builder.build();

            nm.notify(789, n);
     }

Answer 1

I found the solution.. I turns out that the second argument to getBroadcast(Context context, int requestCode, Intent intent, int flags) makes the difference, even when the documentation says

requestCode Private request code for the sender (currently not used).

When a request id is used for each event, the alarm is updated and alarms are created for each event.

The reason is that with two different request codes, the filterEquals(Intent) will be false. Documentation of AlarmManager set(...) says:

If the time occurs in the past, the alarm will be triggered immediately. If there is already an alarm for this Intent scheduled (with the equality of two intents being defined by filterEquals(Intent)), then it will be removed and replaced by this one.

I also changed PendingIntent.FLAG_ONE_SHOT to PendingIndent.FLAG_CANCEL_CURRENT.