iOS SDK 4.0 (Multitasking) issue

I have an iphone application developed on SDK-3.0. Now i want to port that application to SDK 4.0 because of multitasking, i want to keep my app alive in background. Problem is that i could not find any documentation who t开发者_开发技巧each me where i start from to port my app on to SDK4.0 and brief me how i do multitasking in it.

If you just want that your application don't restart when you reenter in, it is automatic

The application includes the "UIApplicationExitsOnSuspend" key in its Info.plist file. By default it's set to false. So nothing to worry about.

You can read the doc for more information if you want to do more in the background.

The third link down in the iOS Developer Portal is called "Supporting Multitasking In Your Applications." I suspect that might be relevant.

In short, if you just want the task switching it should, more or less, Just Work (though you might want to do some extra stuff like remove UIAlertViews and so forth before going into the background).

To actually run in the background is a little more complex and the documentation is really the best place to start. Remember that you can't just run in the background as a Mac app does. It can only do a limited number of things.