alarm trigger immediately and broadcast receiver methods get called immediately

Question

alarm trigger immediately first time working according to time we set but then whatever the time we set it trigger immediately

alarm code

 mCalendar = Calendar.getInstance();
    mHour = mCalendar.get(Calendar.HOUR_OF_DAY);
    mMinute = mCalendar.get(Calendar.MINUTE);
    mYear = mCalendar.get(Calendar.YEAR);
    mMonth = mCalendar.get(Calendar.MONTH) + 1;
    mDay = mCalendar.get(Calendar.DATE);

    timePicker.setOnTimeChangedListener((view, hourOfDay, minute) -> {

        mHour = hourOfDay;
        mMinute = minute;

        //Globals.showToast(getActivity(), hourOfDay + ":" + minute);

    });

    

below code will be called on a button click

int rcode = new Random().nextInt();
    alarmManager = (AlarmManager) Objects.requireNonNull(getActivity()).getSystemService(Context.ALARM_SERVICE);
    if (alarmManager != null) {
        Intent intent = new Intent(getActivity(), AlarmReceiver.class);
         pendingIntent = PendingIntent.getBroadcast(
                this.getActivity(), rcode, intent, PendingIntent.FLAG_UPDATE_CURRENT|  Intent.FILL_IN_DATA);


        mCalendar.set(Calendar.MONTH, --mMonth);
        mCalendar.set(Calendar.YEAR, mYear);
        mCalendar.set(Calendar.DAY_OF_MONTH, mDay);
        mCalendar.set(Calendar.MINUTE, mMinute);
        mCalendar.set(Calendar.HOUR_OF_DAY, mHour);
        mCalendar.set(Calendar.SECOND, 0);
       /* SimpleDateFormat simpleDateFormat = new SimpleDateFormat("dd-MM-yyy hh:mm:a", Locale.ENGLISH);
        Globals.showToast(getActivity(), simpleDateFormat.format(mCalendar.getTimeInMillis()));*/
// Calculate notification time
        Calendar c = Calendar.getInstance();
        long currentTime = c.getTimeInMillis();
        long diffTime = mCalendar.getTimeInMillis() - currentTime;

        // Start alarm using notification time
        alarmManager.set(AlarmManager.ELAPSED_REALTIME, SystemClock.elapsedRealtime() + diffTime,
                pendingIntent);

using above code i m setting alarm but it works perfect only for first time alarm setting. then after using whatever i m setting alarm it triggers immediately.

below receiver toast show immediately

receiver code

public class AlarmReceiver extends BroadcastReceiver {
@Override
public void onReceive(Context context, Intent intent) {

    Globals.showToast(context, "Alarm Time");

}

}

Answer 1

I'm assuming this is the problem:

mCalendar.set(Calendar.MONTH, --mMonth);

This will work the first time, but the next time the value of mMonth will be 1 less than it should be, because you have decreased the value of mMonth. In this case, the trigger time will have already passed, causing the alarm to trigger immediately.

Try this instead:

mCalendar.set(Calendar.MONTH, mMonth - 1);