Q: On the iPhone 3G, is there a quick way to switch between applications in the same way that I use ALT+TAB on my computer? For example, if I am playing a game while listening to music from the iPod app and then receive a text message, when I select reply I am switched over to the SMS application. The only way that I know to get back to the game is to use the home button and then select the game again, which causes it to have to reload. Is there a way to toggle between open apps without having to start over?
A: Unfortunately, no. However, it’s a bit more complicated than simply not providing a fast way to switch between apps. The actual problem is that the iPhone development kit (SDK) that third-party developers use to write applications for the iPhone does not permit these applications to run in the background at all.
This means that as soon as you leave an application for any reason, it must save its state and shut down completely—there is no way to keep the application running in the background when you switch to another app. How well the application later returns to where you left off is entirely dependent on how the developer wrote that particular application. Some applications will return to exactly where you left off, while others will save your current state and give you the option of returning, while still others completely lose track of where you are entirely. We have discovered a wide variation in this behaviour between different iPhone games, so there are no guarantees that any given game will behave well when you exit it to switch to another application.
Note that some of Apple’s own built-in apps on the iPhone do have the ability to run in the background—or at least leave a portion of themselves running so that things like background mail fetching and iPod playback can continue to occur. However, this is the reason why other music playback applications such as Tuner and AOL Radio cannot continue playing once you have exited the application.