Repeat download if connection problems occurred

Issue

In my app, I make an internet connection every 10 minutes via the AlarmManager APIs to download data.

I would like the app to make at least 6 attempts to connect, one every 30 seconds if there a problem with the network connectivity.

Is it possible?

Solution

It isn't possible to do that on a modern Android device where by modern I mean Android 6 or greater.

• 6: Doze [Doze that comes on roughly an hour after the screen is turned OFF]
• 7: Doze++ [Doze that comes on shortly after the screen is turned OFF]
• 8: Background restrictions [Inability to run services that are not in the foreground]

Google's recommended way of doing syncing like this is to use a JobScheduler or Firebase Cloud Messaging if you have luxury of doing a server implementation.

With out knowing all the requirements, it sounds like the app may need to use the AlarmManager if you're determined to sync more frequently than the JobScheduler allows.

There is only 1 API in the AlarmManager that is guaranteed to be called reliably once every 30 seconds and that is setAlarmClock. However, it cannot be used to start a service. It can only send a user-facing alarm and a PendingIntent that will be executed when the user clicks on the alarm.

The two APis most likely to be useful to you are setAndAllowWhileIdle and setExactAndAllowWhileIdle. Both these APIs can be used to start a service. The alarms will execute frequently when the screen is ON or the device is charging. However, when the device is in the power saving mode called Doze they can only execute during Doze maintenance windows. This means they can still run at least once every 9 minutes during most normal doze windows.

Now apps targeting Android 8 must address another new restriction, they have to call startServiceInForeground. A foreground service sets an on going notification like your media player for example. So it makes the user more aware that the service is running and usually gives them an option to stop it.

Now foreground services are 'exempt' from doze, a few things to be aware of:

• When a foreground service is active it prevents the entire device from dozing which greatly increases the battery usage
• In Android 6 foreground services will be dozed anyway unless they are in a separate process due to a framework defect
• I've heard that some devices will eventually kill a foreground service if you leave it running for an extraordinary amount of time

But the real answer to your question is: "Don't do it". Does the app really need to use that much battery and data? Running every 30 seconds is extraordinary and even if was possible it would make the app a "bad citizen" on the phone...

Answered By - Elletlar