Android why are Notifications firing late after replacing JobIntentService with WorkManager? - broadcastreceiver

Question

JobIntentService class is deprecated so I tried to replace the class with WorkManager so I can reset calendar date alarms after a device reboot. When the alarms are triggered a Notification is fired. Unfortunately, Notifications are no longer firing at exact alarm time but with a long delay (1 to 3 minutes after the reboot on a Samsung Galaxy S7 phone running Android 8.0.0).
The RebootReceiver class receives the BOOT_COMPLETED action after the device is rebooted. The RebootReceiver enqueues a OneTimeWorkRequest that should run immediately in the RebootWorker class. The Worker is used to reset all of the pendingIntents for Alarm dates that are saved in a Room database. I originally set up the JobIntentService because there could be hundreds of pending alarms that need to be reset after a device reboot so I wanted the alarm resets to occur in the background. I thought I could use WorkManager to immediately execute after the BOOT_COMPLETED action so that the alarm pendingIntents would be immediately reset. Then I expected the alarms to trigger the Notifications to fire at the exact alarm time.
In my test case using WorkManager, I only set up two calendar due dates so there are only two alarms. I also tried adding ".setExpedited()..." to the OneTimeWorkRequest and that did not change anything. It should not take 1-3 minutes for the Notifications to fire after the alarms are triggered.
Update: I added test for SDK_Int >= 26 to receive ACTION_LOCKED_BOOT_COMPLETED and had same delayed firings for the Notifications.
What am I missing here? Why are Notifications firing so late after the alarms are triggered?
AndroidManifest
<manifest ...
<uses-permission android:name="android.permission.SCHEDULE_EXACT_ALARM" />
<application...
<receiver
android:name=".RebootReceiver"
<intent-filter>
<category android:name="android.intent.category.DEFAULT" />
<action android:name="android.intent.action.LOCKED_BOOT_COMPLETED" />
<action android:name="android.intent.action.BOOT_COMPLETED" />
</receiver>
</application>
</manifest>
RebootReceiver
public class RebootReceiver extends BroadcastReceiver {
#Override
public void onReceive(Context context, Intent intent) {
if (intent != null) {
String action = intent.getAction();
if (action != null) {
if (action.equals(Intent.ACTION_LOCKED_BOOT_COMPLETED) || action.equals(Intent.ACTION_BOOT_COMPLETED) ||
action.equals(QUICKBOOT_POWERON) || action.equals(HTC_QUICKBOOT)) {
resetAlarmsWorkRequest = new OneTimeWorkRequest.Builder(RebootWorker.class)
// this also did not work: ".setExpedited(OutOfQuotaPolicy.RUN_AS_NON_EXPEDITED_WORK_REQUEST)"
.build();
WorkManager.getInstance(context).enqueue(resetAlarmsWorkRequest);
}
}
}
}
}
RebootWorker
public class RebootWorker extends Worker {
private CardRepository reposit;
private AlarmManager alarmManager;
private Intent brIntent3;
private PendingIntent pendingIntent3;
private Context mContext;
public RebootWorker(
#NonNull Context context,
#NonNull WorkerParameters parameters) {
super(context, parameters);
mContext = context;
}
#SuppressLint("UnspecifiedImmutableFlag")
#NonNull
#Override
public Result doWork() {
try {
reposit = new CardRepository(mContext);
alarmManager = (AlarmManager) getApplicationContext().getSystemService(Context.ALARM_SERVICE);
Calendar cal3 = Calendar.getInstance();
List<Card> resetNotificationsList = reposit.getNotifications();
// Cycle through the Room database rows to get the Notifications data.
for (Card card: resetNotificationsList) {
if (card == null) {
break;
}
cal3.setTimeInMillis(quickcard.getDuedatentime());
if (cal3.getTimeInMillis() > System.currentTimeMillis()) {
brIntent3 = new Intent(mContext, AlarmReceiver.class);
brIntent3.setAction("DueAlarm");
brIntent3.setData(Uri.parse("http://" + quickcard.getId()));
if (Build.VERSION.SDK_INT >= 23) {
pendingIntent3 = PendingIntent.getBroadcast(getApplicationContext(),0, brIntent3,
PendingIntent.FLAG_IMMUTABLE | PendingIntent.FLAG_UPDATE_CURRENT);
} else {
pendingIntent3 = PendingIntent.getBroadcast(getApplicationContext(),0, brIntent3,
PendingIntent.FLAG_UPDATE_CURRENT);
}
int SDK_INT3 = Build.VERSION.SDK_INT;
if (SDK_INT3 >= Build.VERSION_CODES.M) {
if (alarmManager != null) {
alarmManager.setExactAndAllowWhileIdle(
AlarmManager.RTC_WAKEUP,
cal3.getTimeInMillis(), pendingIntent3);
// I also tried "alarmManager.setAlarmClock()..." here, and that did not work either.
}
} else if (SDK_INT3 >= Build.VERSION_CODES.KITKAT) {
if (alarmManager != null) {
alarmManager.setExact(AlarmManager.RTC_WAKEUP, cal3.getTimeInMillis(), pendingIntent3);
}
} else {
if (alarmManager != null) {
alarmManager.set(AlarmManager.RTC_WAKEUP, cal3.getTimeInMillis(), pendingIntent3);
}
}
}
}
return Result.success();
} catch (Throwable throwable) {
Log.e(TAG,"Error tring to reset alarms after devive reboot", throwable);
return Result.failure();
}
}
}

Answer 1

Since you want exact alarm, AlarmManager is your choice.
I don't think WorkManager should be used in your case, since it offers no exact guarantee WHEN it will be executed, it just gives you a promise that it will sometime in the future. All this to improve battery life.
From documentation:
Immediate: Tasks that must begin immediately and complete soon. May be expedited.
Expedited work:
You can use WorkManager to schedule immediate work for execution in the background. You should use Expedited work for tasks that are important to the user and which complete within a few minutes.
So 1 to 3 minutes is what Expedited work offers to you.