My android Application instance(Application class) is destroyed after I stay my application in background after 2-3 minutes

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http://stackoverflow.com – I use Application class to store my android application global parameters.But when I go to other app and stay my app to background for about several minutes, my app can not run again. Because I get parameters from the Application class but now it becomes empty. My question is why it like that and how to solve this problem? And I also saw a thread follows: Returning after a period of inactivity in my Android Application causes destroy set Values The answer is using onSaveInstanceState(). But how can I save all my application parameters in it? Thank you . (HowTos)