How to check if AlarmManager already has an alarm set?

Question

Following up on the comment ron posted, here is the detailed solution. Let's say you have registered a repeating alarm with a pending intent like this:

Intent intent = new Intent("com.my.package.MY_UNIQUE_ACTION");
PendingIntent pendingIntent = PendingIntent.getBroadcast(context, 0, 
                                      intent, PendingIntent.FLAG_UPDATE_CURRENT);
Calendar calendar = Calendar.getInstance();
calendar.setTimeInMillis(System.currentTimeMillis());
calendar.add(Calendar.MINUTE, 1);

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

The way you would check to see if it is active is to:

boolean alarmUp = (PendingIntent.getBroadcast(context, 0, 
        new Intent("com.my.package.MY_UNIQUE_ACTION"), 
        PendingIntent.FLAG_NO_CREATE) != null);

if (alarmUp)
{
    Log.d("myTag", "Alarm is already active");
}

The key here is the FLAG_NO_CREATE which as described in the javadoc: if the described PendingIntent **does not** already exists, then simply return null (instead of creating a new one)

For others who may need this, here's an answer.

Use adb shell dumpsys alarm

You can know the alarm has been set and when are they going to alarmed and interval. Also how many times this alarm has been invoked.

Working example with receiver (the top answer was just with action).

//starting
AlarmManager alarmManager = (AlarmManager) getActivity().getSystemService(Context.ALARM_SERVICE);
Intent intent = new Intent(getActivity(), MyReceiver.class);
intent.setAction(MyReceiver.ACTION_ALARM_RECEIVER);//my custom string action name
PendingIntent pendingIntent = PendingIntent.getBroadcast(getActivity(), 1001, intent, PendingIntent.FLAG_CANCEL_CURRENT);//used unique ID as 1001
alarmManager.setRepeating(AlarmManager.RTC_WAKEUP, System.currentTimeMillis(), aroundInterval, pendingIntent);//first start will start asap

//and stopping
Intent intent = new Intent(getActivity(), MyReceiver.class);//the same as up
intent.setAction(MyReceiver.ACTION_ALARM_RECEIVER);//the same as up
PendingIntent pendingIntent = PendingIntent.getBroadcast(getActivity(), 1001, intent, PendingIntent.FLAG_CANCEL_CURRENT);//the same as up
alarmManager.cancel(pendingIntent);//important
pendingIntent.cancel();//important

//checking if alarm is working with pendingIntent
Intent intent = new Intent(getActivity(), MyReceiver.class);//the same as up
intent.setAction(MyReceiver.ACTION_ALARM_RECEIVER);//the same as up
boolean isWorking = (PendingIntent.getBroadcast(getActivity(), 1001, intent, PendingIntent.FLAG_NO_CREATE) != null);//just changed the flag
Log.d(TAG, "alarm is " + (isWorking ? "" : "not") + " working...");

It is worth to mention:

If the creating application later (process) re-retrieves the same kind of PendingIntent (same operation, same Intent's - action, data, categories, components, flags), it will receive a PendingIntent representing the same token if that is still valid, and can thus call cancel() to remove it.

In short, your PendingIntent should have the same features (operation and intent's structure) to take control over it.

Note this quote from the docs for the set method of the Alarm Manager:

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

If you know you want the alarm set, then you don't need to bother checking whether it already exists or not. Just create it every time your app boots. You will replace any past alarms with the same Intent.

You need a different approach if you are trying to calculate how much time is remaining on a previously created alarm, or if you really need to know whether such alarm even exists. To answer those questions, consider saving shared pref data at the time you create the alarm. You could store the clock timestamp at the moment the alarm was set, the time that you expect the alarm to go off, and the repeat period (if you setup a repeating alarm).