How to trigger an alarm only once in Android?

问题:

I set an alarm when the user lands on a certain activity, which is triggered after a certain time. How can I check if this alarm has already been triggered or not, so that it doesn't get set again if the user goes back to this activity ? I can only prevent the alarm getting set again if it's already scheduled but not triggered with this :

alarmIntent = PendingIntent.getBroadcast(context, requestCode, intent, PendingIntent.FLAG_NO_CREATE);
    if (alarmIntent != null) {
        // Alarm is already set
        return;
    }
    alarmIntent = PendingIntent.getBroadcast(context, requestCode, intent, 0);

But this does not work if it's already triggered, as the alarm will be deleted afterwards so alarmIntent will be null

回答1:

You can make use of shared preferences to check whether it is set or not.

if(!setFlag)
{
    Intent myIntent = new Intent(FirstActivity.this, LogoutService.class);
    pendingIntent = PendingIntent.getService(FirstActivity.this, 0, myIntent, 0);
    AlarmManager alarmManager = (AlarmManager)getSystemService(ALARM_SERVICE);
    Calendar calendar = Calendar.getInstance();
    calendar.setTimeInMillis(System.currentTimeMillis());
    calendar.add(Calendar.MINUTE, 10); //Minutes
    alarmManager.set(AlarmManager.RTC_WAKEUP, calendar.getTimeInMillis(), pendingIntent);
}

回答2:

Change PendingIntent PendingIntent.FLAG_CANCEL_CURRENT

alarmIntent = PendingIntent.getBroadcast(context, requestCode, intent, PendingIntent.FLAG_CANCEL_CURRENT);

回答3:

You can just create a file the first time the alarm is run, and on next alarm runs you can check that the file already exists and you don't have to run the alarm again.