Restrict installation to multitasking-capable devices?

Is there a way to restrict the installation of my app to allow only multitasking-capable devices?

My app needs to do some background task (finish a download in the background when minimized). I could work around it (abort the task and start over next time), but that would add complexity (and bugs), and I can do without supporting the iPhone 3G/equivalent iPod Touch.

The .plist file lets you set required device capabilities (OpenGL ES 2.0, etc.), but mu开发者_如何转开发ltitasking is nowhere to be found.

I could set the minimum deployment target to iOS 4.3, but I don't want to miss on iPhone 3GS/iPhone 4 users who aren't savvy enough to upgrade their OS and might still be on 4.2 or less.

Any ideas?

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EDIT: I found this discussion Exclude devices that do not support multitasking

...So it seems the best way is to limit support to only armv7 CPUs.

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As suggested on my own edit, it seems that there is no 'required device capability' that corresponds exactly to multitasking-capable devices.

However, these very same devices just happen to be exactly the same ones that support OpenGL ES 2.0, and that is in the list of device capabilities you can specify in your Info.plist file. But this is at most a (perfect) work-around.

The correct thing to do would be to set a deployment target of 4.3, since only multitasking-capable devices can run that OS. However, it is possible that some multitasking-capable device might still be running iOS 4.2 or less. This is less of a concern as iOS 4 becomes older: in the verge of the iOS 6 release, a few months from now, dropping support for iOS 4.x altogether is a more viable option.