I'm working on an app that needs to run through a protocol from beginning to end. How do I force the app to always start at the beginning when brought back from the background, regardless of where it was left. Thanks
If your goal is to restart the app from scratch at every start up, simply add/change the key UIApplicationExitsOnSuspend to YES in your info.plist file
Here's the relevant link in the documentation http://developer.apple.com/library/ios/#documentation/general/Reference/InfoPlistKeyReference/Articles/iPhoneOSKeys.html
One option is to use exit(). However, that method is only useful for testing/programming purposes. Apple will not accept that being in your code.
Another option would be to create a global session similar to the method used by most social media API's, and in your App Delegate's:
- (void)applicationDidEnterBackground:(UIApplication *)application
set the global session to closed. Then just set your protocol logic to restart if the session is closed.
I hope that helps!
write your application starting code in applicationDidBecomeActive method, because this method calls both time when you start your application first time & also when you cames from background
来源：https://stackoverflow.com/questions/14533997/how-do-i-force-an-app-to-always-start-from-scratch-when-it-returns-from-the-back