Android 6.0 : UsageEvents method 'usageStatsManger.queryEvents()' is giving count 0 (zero)

I have created a Service in which I check for foreground activity using 'UsageEvents'.

private void getForegroundActivity() {
        String packageName = "";
        String className = "";
        Calendar cal_begin = Calendar.getInstance();
        cal_begin.set(Calendar.YEAR, -1);
        long _begTime = cal_begin.getTimeInMillis(); 
        long _endTime = System.currentTimeMillis();
        UsageStatsManager usageStatsManager = (UsageStatsManager)  this.getSystemService(Context.USAGE_STATS_SERVICE);

        if (usageStatsManager != null) {
            UsageEvents queryEvents = usageStatsManager.queryEvents(_begTime, _endTime);

            if (queryEvents != null) {
                UsageEvents.Event event = new UsageEvents.Event();

                while (queryEvents.hasNextEvent()) {
                    UsageEvents.Event eventAux = new UsageEvents.Event();
                    queryEvents.getNextEvent(eventAux);

                    if (eventAux.getEventType() == UsageEvents.Event.MOVE_TO_FOREGROUND) {
                        event = eventAux;
                    }
                }

                packageName = event.getPackageName();
                className = event.getClassName();
   }

The above code works fine and gives proper foreground activity, but after some time(let's say 2-3 hours later), the 'queryEvents(_begTime, _endTime)'returns '0'(zero) counts !!

Is there some other way of using usageStatsManager.queryEvents() in Service ?

Any other pointers, ideas are appreciated.

The events returned by queryEvents() are kept by the system only for a few days. So, you might have to maintain a local database to maintain those stats locally. There is no problem in your code.

For more information about queryEvents() method and UsageStatsManager, checkout the below link :

UsageStatsManager queryEvents