iphone how do I detect my app was pushed to background?

I had written an app for iPhone 3. The app 开发者_运维百科calls safari and while it does that it exits out. Next time when it is called it loads from scratch.

But with iPhone 4 this behavior has changed. I find that my app was in the same where I left it before I opened safari.

How do I exit my app while it is sent to background ? (iPhone 3 like behavior)

or is there any delegate that I can use to detect if my app has gone to background and again came to forground ?

thank you !

You can set a key in Info.plist called UIApplicationExitsOnSuspend to YES.

You can implement applicationWillResignActive: which is called when an app is terminating or on iOS4 if it is going into the background.