android - Service is killed in sleep mode.Why?

Question

I've read just about every Stackoverflow answer that exists on this topic, but none of them worked.

Goal: Keep my service running 24/7, all the time

Problem: Whenever my device is on sleep mode for an hour or more, the service is killed

---

What I've tried to fix it:

• Returning START_STICKY from onStartCommand() and using startForeground()

      public int onStartCommand(Intent intent, int flags, int startId) {
  
          notification = makeStickyNotification(); //I've simplified the irrelevant code, obviously this would be a real notification I build
  
          startForeground(1234, notification);
          return START_STICKY;
          }
  

This works fine, and it even restarts my service whenever the device is low on memory, but it is not enough to fix the problem that occurs when my device goes to sleep for a while.

• Using Alarm Manager in onCreate() of my Activity and in onStartCommand() of my Service to call a Broadcast Receiver that calls my service

          Intent ll24 = new Intent(this, AlarmReceiver.class);
  
          PendingIntent recurringLl24 = PendingIntent.getBroadcast(this, 0, ll24, PendingIntent.FLAG_CANCEL_CURRENT);
  
          AlarmManager alarms = (AlarmManager) getSystemService(Context.ALARM_SERVICE);
  
          alarms.setRepeating(AlarmManager.RTC_WAKEUP, System.currentTimeMillis(), 1000*60, recurringLl24); // Every minute
  

This helps keep my service active, but again, doesn't solve my problem

• Using Schedule Task Executor to keep it alive

   if (scheduleTaskExecutor == null) {
  
          scheduleTaskExecutor = Executors.newScheduledThreadPool(1);
  
          scheduleTaskExecutor.scheduleAtFixedRate(new mainTask(), 0, 1, TimeUnit.SECONDS);
  
      }
  ...    
  class mainTask implements Runnable {
  
  public void run() {
      // 1 Second Timer
     }
  }
  

  This also just keeps the service active but doesn't keep it alive after a long sleep.

• Separate task Manifest

  android:launchMode="singleTop"

This did nothing

How can I (1) test this issue without having to put my phone to sleep and check every hour and (2) keep my service running despite the device going to sleep?

Answer 1

Your service was killed by Doze or Standby mode of Android. That was introduced in Android 6.0 (API level 23).

Doze restrictions

The following restrictions apply to your apps while in Doze:

• Network access is suspended.
• The system ignores wake locks.
• Standard AlarmManager alarms (including setExact() and setWindow()) are deferred to the next maintenance window.
• If you need to set alarms that fire while in Doze, use setAndAllowWhileIdle() or setExactAndAllowWhileIdle().
• Alarms set with setAlarmClock() continue to fire normally — the system exits Doze shortly before those alarms fire.
• The system does not perform Wi-Fi scans.
• The system does not allow sync adapters to run. The system does not allow JobScheduler to run.

So system ignored your Alarm Clocks, Scheduler, etc.

In Android Oreo release Android defined limits to background services.

To improve the user experience, Android 8.0 (API level 26) imposes limitations on what apps can do while running in the background.

Still if app need to run its service always, then we can create foreground service.

Background Service Limitations: While an app is idle, there are limits to its use of background services. This does not apply to foreground services, which are more noticeable to the user.

So create a foreground service. In which you will put a notification for user while your service is running. See this answer (There are many others)

Now what if you don't want a notification for your service. A solution is for that.

You can create some periodic task that will start your service, service will do its work and stops itself. By this your app will not be considered battery draining.

You can create periodic task with Alarm Manager, Job Scheduler, Evernote-Jobs or Work Manager.

• Instead of telling pros & cons of each one. I just tell you best. Work manager is best solution for periodic tasks. Which was introduced with Android Architecture Component.
• Unlike Job-Scheduler(only >21 API) it will work for all versions.
• Also it starts work after a Doze-Standby mode.
• Make a Android Boot Receiver for scheduling service after device boot.

I created forever running service with Work-Manager, that is working perfectly.