On Feb 2, 11:36 am, Miroslav Pokorny <[email protected]>
wrote:
> > No only Apple is allowed to deliver background running capable apps.
>
> Everyone else must write foreground only apps, which are notified and
> eventually killed after a shutdown grace period whenever someone hits the
> home button or similar. Apple apps on the other hand dont die they just live
> in the background and keep executing if they want.

Not true.  Since iOS 4.0 apps go into the background when the user
hits the home button or switches between apps on devices that support
multi-tasking (iPhone 3GS and up; before that, the iPhone and the iPod
Touch only had 128 MB RAM which isn't enough). This way, the come back
a lot quicker than starting from scratch and are still at the point
you left them - Apple calls this "fast app switching".  You just need
to re-compile your app to get this feature. Your app still can get
killed if iOS runs out of memory or the user switches off his device,
so you're supposed to save your state and reduce memory usage before
entering the background state (e.g., emptying image caches and so
on).  For more details, see here:
http://www.cocoanetics.com/2010/07/understanding-ios-4-backgrounding-and-delegate-messaging/

Additionally, your app can also register background services, such as
playing audio files, listening for location updates or waiting for
VoIP calls.  These services then do run in the background in what you
could call multi-tasking.  Some apps that always want to stay in
memory use a loophole - they play a silent MP3 file, so they don't get
killed by the system (typically not enabled by default).

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