how to update fragment on clock time

问题:

I'm trying to update fragment on clock time, say for example 8PM, with below logic. Unfortunately, it doesn't update the fragment. Any help/reference would be appreciated.

What I did:

1. registered an AlarmManager in app's Application class as below:

       alarmMgr = (AlarmManager) context.getSystemService(Context.ALARM_SERVICE);
       Intent intent = new Intent().setAction(AppConstants.INTENT_ACTION_UPDATE_DASHBOARD);
       alarmIntent = PendingIntent.getBroadcast(context, 0, intent, 0);
   
       // Set the alarm to start at Consulting start time
       Calendar calendar = Calendar.getInstance();
       calendar.setTimeInMillis(System.currentTimeMillis());
       calendar.set(Calendar.HOUR_OF_DAY, hour);
       calendar.set(Calendar.MINUTE, minute);
       alarmMgr.set(AlarmManager.RTC_WAKEUP, calendar.getTimeInMillis(), alarmIntent);
   

2. Listens for AlarmManager in Fragment as below:

   LocalBroadcastManager.getInstance(getActivity()).registerReceiver(mDashboardUpdateReceiver, new IntentFilter
           (AppConstants.INTENT_ACTION_UPDATE_DASHBOARD));
   

3. and performs actions if broadcast receives:

   private BroadcastReceiver mDashboardUpdateReceiver = new BroadcastReceiver() {
        @Override
        public void onReceive(Context context, Intent intent) {
            Log.d(TAG, "Dashboard updating...");
            updateCounters();
        }
   

回答1:

First, a PendingIntent does not trigger a local broadcast. You cannot use LocalBroadcastManager here.

Second, using AlarmManager to update a UI is rather odd. If your UI exists, you have a process running, so you could use something in-process (e.g., ScheduledExecutorService) rather than fussing with AlarmManager.

Third, you are not taking into account that set(Calendar.HOUR_OF_DAY, hour) and calendar.set(Calendar.MINUTE, minute) might change the Calendar to be in the past. Imagine if you execute your first code snippet at 23:00, with hour set to be 22 and minute set to be 0. The Calendar object that you create will be for today, but for 22:00 today, which was an hour before now (23:00). You need to check the Calendar, see if it is in the past, and if so, add() a day or otherwise adjust it to some future time.