Unable to create UIBackgroundModes key in Info.plist for iOS4

问题

I have an audio application which works great for iPhone 3.1.x versions.

I am trying to upgrade it to iOS4.0 to work in multitasking environment. When I try to create a new UIBackgroundModes key in info.plist, it ("Required Background Modes") doesn't show up in drop down list?

I also upgraded the Xcode SDK to 3.2.3, Base SDK to 4.0, deployment target to 4.0 but still UIBackgroundModes ("Required Background Modes") won't show up in info.plist drop down list.

I also created test project for 4.0, and its info.list drop down list has "Required Background Modes".

Did I miss something?

回答1:

You can add the key manually by edit the .plist file

    <key>UIBackgroundModes</key>
    <array>
            <string>audio</string>
    </array>

回答2:

Be sure that if you create the UIBackgroundModes item in Xcode (not by editing the XML manually) that you create the new key as type ARRAY, then add a new item (it will appear as "Item 0" by default) with a value of "audio". If you simply create a string key with value "audio", it will not work.

回答3:

Re Woodmantech's answer: Xcode 3.2 changed the nomenclature a bit when adding this key in Xcode. The key is called "Required background modes" and Item 0 should be set to "App plays audio." Both are available through the GUI dropdown menu

来源：https://stackoverflow.com/questions/3251793/unable-to-create-uibackgroundmodes-key-in-info-plist-for-ios4