Android get actual time ( When internet is off and device time is incorrect)

Question

As per question stated I need actual time. For example in my app I have to show a specific pop up to all the users at 8 AM national time. App runs in a specific country. What if there device time is incorrect ? I can get the time by an api . What if device don't have interenet ? I was thinking about taking the track of time when ever I got internet. For example, If I got internet I hit an api to get the time and store that time to keep track of it. Any other sloution ?

Answer 1

What about this solution: GPS-time in Android?

This will require the GPS receiver though.

Answer 2

You can't get the real timestamp if your the Time set in the device is wrong..

Edit:- There is only a solution,I could found using phone internet is:-

You can give time from public server time. remember to add INTERNET permission in manifest.

String TIME_SERVER = "url"; 
NTPUDPClient timeClient = new NTPUDPClient(); 
InetAddress inetAddres=InetAddres.getByName(TIME_SERVER);
TimeInfo timeInfo = timeClient.getTime(inetAddress);
long returnTime = timeInfo.getMessage().getTransmitTimeStamp().getTime(); 
Date time = new Date(returnTime);

Answer 3

You'd need to use UTC. If you really, really need this I would have the app keep record of the time as UTC at the moment of installation (you know the user has internet at this time, so you can take advantage of that) and then have the app keep track of this UTC internally.

You could add seconds to the UTC as they pass while the app is open, and then localizing that time is trivial. You could then use the devices time to see how long it has been since the app was last opened (you'd need to create a timestamp each time the app closes and opens) and convert that time to seconds and add it to your apps stored UTC. Again, localizing this time is a triviality. I would also check if the user has internet any time they open the app and if they do have internet, get the correct UTC and update your updates internal UTC.

If you can get permission to run silently and count seconds in the background this becomes even easier, and you can give real time notifications. It's not perfect but I'm certain it could work.