Inactivity is a very important EVENT. For many apps if the user does not interact with it for a certain number of seconds its time to reset the app and go back to main act
Just stumbled upon this question as I've answered something similar just now.
Personally, I'd opt for option 2 that you have suggested, and put a timer into a singleton so its available across all activities. Theres no need for a separate countdown timer unless you have a specific requirement to react different under different features of your application.
Why would you want to reset the timer in the onCreate? You should do that each time the user interacts with the application, such as in the activity.onUserInteraction() method.
To quote from my previous answer:
You'll need to invest a little thought into exactly what your requirements are here, but from what I can tell, you want to keep track of the user interactions and if a time limit expires since the last interaction, perform some action, in your case logging them out of your application.
Firstly, you'll need some place that you can track when the last interaction occured, since you'll want this to be application wide you could use a singleton to hold this, or override the Application class, either way should do.
Next, you'll need to start tracking user interactions. From your activities, you can override the onUserInteraction method, this gets invoked anytime the user interacts with the application such as key event. Each time you hit this method, update your singleton and let it know something has happened, with a timestamp.
Finally, you'll need some kind of looping check to constantly check if anything has happened recently. Theres various was of doing this, you could have a continuous loop that compares current timestamp to the last recorded event, a bit of draft code :
while(true)
{
if (timeLastEventRecorded < (now - 15))
{
//nothing has happened in 15 minutes, so take corrective action
}
}
Presumably you'll already have some code in your application that takes care of logouts, such as when the user clicks "logout", you should just be able to invoke that in the sample above.