UIApplicationDelegate changed a lot with the introduction of multitasking in iOS4 (see Dr. Touch’s post and charts [although there are still some small omissions and inaccuracies there]).
UIApplicationDelegate was not the only class affected.
UIViewController‘s behaviour is slightly changed in the presence of multitasking: namely the
If your iOS4-built app is running on iPhone OS 3, or if
UIApplicationExitsOnSuspend is set to
true, then when the user presses the Home button, the frontmost view controller’s
viewDidDisappear: methods will be called before the app exits. However, if
false and you’re running on a multitasking-enabled device (iPhone 3GS or higher; iPod touch 3rd generation),
viewDidDisappear: are not called as it enters the background.
That was a messy couple of sentences so here’s a chart!
|UIApplicationExitsOnSuspend?||multitasking-capable device and OS?||When Home button is pressed:|
It’s subtle, but it might make a difference to your code.