小部件，AlarmManager和KitKat API19

Question

Since API19 (KitKat), AlarmManager broadcasts are not acted on immediately, but batched together.
The documentation says that it should act immediately in KitKat if the app is targeted to API 18 or less, but this doesnt seem to work.
Example, my clock widget is targeted to API 18 but it doesnt update when required on KitKat emulator (i dont have a device to test on). I read online that many people report their old clock widgets no longer updating on their KitKat devices.
The AlarmManager doc suggests this is to avoid wakeups, but it affects my RTC alarm also.


The docs suggest setExact, but this is only for API19+. Is there a way to trigger updates that will be processed immediately on API8+ including API19? Or is it better to add a separate AlarmManager for API19+?
What could be a good solution for getting widgets to update properly on API19+ and still work properly on older devices?

Answer 1

One strategy that has a single solution for both pre-API19 and API19+ that works for me:
replace AlarmManager's setRepeating() broadcast with a new set() / setExact() created each time the widgets are updated.
This strategy allows continued use of AlarmManager's RTC alarm type, which doesnt trigger while the phone is asleep.
It causes the widget to update at the intended time on any API and keeps my widget as power efficient as it was using setRepeating() .

Instead of creating a setRepeating() alarm in the onEnabled method in the "widget manager" class...
Create a set() for API18 or less, or setExact() for API19+ in the "Update Widget" class, after the widget update code is run. Everytime the widget is updated, a new alarm is set for whatever time is next required.
Here is a section of code (incomplete) from within onStartCommand() in the "updateservice" class, that is called by both onEnabled() and the broadcast receiver class.

 public int onStartCommand(Intent intent, int flags, int startId) { Log.w(LOG, "UpdateService.onStartCommand activated"); // reset the time dependent millis addition long alarmAddMillis = 0; // get time instance and values Calendar rightNow = Calendar.getInstance(); int thisMin = rightNow.get(Calendar.MINUTE); int thisHour = rightNow.get(Calendar.HOUR); // set correct hour values to update widget nextHour = thisHour + 1; if (thisHour == 0) {thisHour = 12;} if (nextHour == 13) {nextHour = 1;} // set text values based on minutes // set the values for the next alarm time if (thisMin >= 0 && thisMin <= 6) { clockH = thisHour; nextAlarmMin = 8; alarmAddMillis = 0;} if (thisMin >= 7 && thisMin <= 21) { clockH = thisHour; nextAlarmMin = 22; alarmAddMillis = 0;} if (thisMin >= 21 && thisMin <= 35) { clockH = thisHour; nextAlarmMin = 37; alarmAddMillis = 0;} if (thisMin >= 36 && thisMin <= 50) { clockH = nextHour; nextAlarmMin = 52; alarmAddMillis = 0;} if (thisMin >= 51 && thisMin <= 59) { clockH = nextHour; nextAlarmMin = 8; alarmAddMillis = 3600000;} 

----CODE FOR UPDATING THE WIDGETS GOES IN HERE----

  // cancel any unsent alarm if (alarmManager != null){ alarmManager.cancel(pendingIntent); Log.w(LOG, "UpdateService.onStartCommand unsent alarm canceled");} // SET UP THE NEXT ALARM // set the time using values set above Calendar nextAlarm = Calendar.getInstance(); // add one hour of millis if its for the next hour nextAlarm.setTimeInMillis(System.currentTimeMillis() + alarmAddMillis); // set the correct minute nextAlarm.set(Calendar.MINUTE, nextAlarmMin); nextAlarm.set(Calendar.SECOND, 0); nextAlarm.set(Calendar.MILLISECOND, 0); // request the alarm alarmManager = (AlarmManager)getSystemService(Context.ALARM_SERVICE); Intent usIntent = new Intent(this, AlarmReceiver.class); pendingIntent = PendingIntent.getBroadcast(this, 0, usIntent, 0); // ACCOUNT FOR DIFFERENT APIs HERE... // use onExact for API19+ int currentApiVersion = android.os.Build.VERSION.SDK_INT; if (currentApiVersion <= 18) { alarmManager.set(AlarmManager.RTC, nextAlarm.getTimeInMillis(), pendingIntent); Log.w(LOG, "FuzzyTimeWidget.onEnabled pre-kitkat AlarmManager requested"); }else{ alarmManager.setExact(AlarmManager.RTC, nextAlarm.getTimeInMillis(), pendingIntent); Log.w(LOG, "FuzzyTimeWidget.onEnabled API19+ AlarmManager requested"); } 

The only code required to manage the different API's is at the point of setting the alarm. Just choosing set() or setExact() . All the other code is for any API.
In my case, I use nextAlarmMin to set the exact time for the next Alarm, which goes off 4 times per hour at 8, 22, 37, 52.
For widgets that update every minute, I'm not sure how this strategy would be for the battery life.