Android – AlarmManager not working in sleep mode

alarmmanagerandroidandroid-alarms

I have set an AlarmManagr with a repeat time. Here is my method by which I am setting it:

public void setAlarmManager(Context context, Intent intent) {           
    PendingIntent pendingIntent;
    pendingIntent  = PendingIntent.getService(context, 0, intent, 0);               
    AlarmManager alarmManager =
        (AlarmManager)context.getSystemService(context.ALARM_SERVICE);

    Calendar calendar = Calendar.getInstance();
    calendar.setTimeInMillis(System.currentTimeMillis());
    calendar.add(Calendar.SECOND, 10);
    alarmManager.setRepeating(AlarmManager.RTC_WAKEUP, 
                              calendar.getTimeInMillis(), 
                              40000, pendingIntent);                   
}

This works fine except when my device goes into sleep mode the the alarm stops working until I awake my device manually. After waking the device the AlarmManager start working again.

How to keep the manager running even in sleep mode?

Best Solution

It is because your PendingIntent is calling to a service and not to a BroadcastReceiver which means the device can go back to sleep before your service is even created. If you move to a broadcast receiver it "should" stay awake until the onReceive is complete of the BroadcastReceiver which means you will have time to get a wakelock and start your service. Even if you move to a BroadcastReceiver you will want to acquire a wakelock until you have completed your processing if it's going to take more than 10 seconds (which is the limit of a BroadcastReceiver).

This is taken from paragraph 2 of the android documentation of AlarmManager:

"... If your alarm receiver called Context.startService(), it is possible that the phone will sleep before the requested service is launched. To prevent this, your BroadcastReceiver and Service will need to implement a separate wake lock policy to ensure that the phone continues running until the service becomes available."

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