Why is my iOS app not showing up in other apps' “Open in” dialog?

Question

I am trying to implement the registering process that allows my iOS app to show up in the "Open in" list of other applications (as described in Apple's Document Interaction Programming Topics). I want my app to be able to handle audio from any app that will provide a standard audio file format (MP3, AIFF, WAV, etc.).

As I understand it, all I should need to do is add the CFBundleDocumentTypes key, with relevant subdata, to my app's Info.plist. This is what I put in (via Xcode 4's Document Types editor):

<key>CFBundleDocumentTypes</key>
<array>
    <dict>
        <key>CFBundleTypeIconFiles</key>
        <array>
            <string>scrubbulator-icon</string>
        </array>
        <key>CFBundleTypeName</key>
        <string>Audio</string>
        <key>LSHandlerRank</key>
        <string>Alternative</string>
        <key>LSItemContentTypes</key>
        <array>
        <string>public.mp3</string>
        </array>
    </dict>
</array>

The addition of this code is not displaying my app in apps' "Open in" menu (I am testing on an iPhone, using an MP3 in Dropbox as the file source. The apps AudioMemos and Evernote are both displayed for an MP3 file in Dropbox, so I know the format is supported). Is there something obvious I'm doing wrong, or is there something else I need to implement?

(Note: I have not set up a UTExportedTypeDeclarations item in my Info.plist, as I understand these to be necessary only for custom UTIs. As I'm using System UTIs I believe it shouldn't be necessary, but please correct me if I am wrong.)

EDIT

I've added the following Exported Type UTI, with no success:

<key>UTExportedTypeDeclarations</key>
<array>
    <dict>
        <key>UTTypeConformsTo</key>
        <array>
        <string>kUTTypeMP3</string>
        </array>
        <key>UTTypeDescription</key>
        <string>Audio file</string>
        <key>UTTypeIdentifier</key>
        <string>kUTTypeMP3</string>
        <key>UTTypeTagSpecification</key>
        <dict>
        <key>public.filename-extension</key>
        <array>
            <string>mp3</string>
        </array>
        </dict>
    </dict>
</array>

Answer 1

For all standard file format:

<key>CFBundleDocumentTypes</key>
<array>
    <dict>
        <key>CFBundleTypeName</key>
        <string>Unknown File</string>
        <key>LSHandlerRank</key>
        <string>Alternate</string>
        <key>LSItemContentTypes</key>
        <array>
            <string>public.calendar-event</string>
            <string>public.database</string>
            <string>public.executable</string>
            <string>public.data</string>
            <string>public.content </string>
            <string>public.item</string>
        </array>
    </dict>
    <dict>
        <key>CFBundleTypeName</key>
        <string>Video</string>
        <key>LSHandlerRank</key>
        <string>Alternate</string>
        <key>LSItemContentTypes</key>
        <array>
            <string>public.video</string>
        </array>
    </dict>
    <dict>
        <key>CFBundleTypeName</key>
        <string>Image</string>
        <key>LSHandlerRank</key>
        <string>Alternate</string>
        <key>LSItemContentTypes</key>
        <array>
            <string>public.image</string>
        </array>
    </dict>
    <dict>
        <key>CFBundleTypeName</key>
        <string>Web Archive</string>
        <key>LSHandlerRank</key>
        <string>Alternate</string>
        <key>LSItemContentTypes</key>
        <array>
            <string>com.apple.webarchive</string>
        </array>
    </dict>
    <dict>
        <key>CFBundleTypeName</key>
        <string>iWork Keynote</string>
        <key>LSHandlerRank</key>
        <string>Alternate</string>
        <key>LSItemContentTypes</key>
        <array>
            <string>com.apple.keynote.key</string>
            <string>com.apple.iwork.keynote.key</string>
            <string>com.apple.iwork.keynote.kth</string>
        </array>
    </dict>
    <dict>
        <key>CFBundleTypeName</key>
        <string>iWork Numbers</string>
        <key>LSHandlerRank</key>
        <string>Alternate</string>
        <key>LSItemContentTypes</key>
        <array>
            <string>com.apple.numbers.numbers</string>
            <string>com.apple.iwork.numbers.numbers</string>
            <string>com.apple.iwork.numbers.template</string>
        </array>
    </dict>
    <dict>
        <key>CFBundleTypeName</key>
        <string>iWork Pages</string>
        <key>LSHandlerRank</key>
        <string>Alternate</string>
        <key>LSItemContentTypes</key>
        <array>
            <string>com.apple.page.pages</string>
            <string>com.apple.iwork.pages.pages</string>
            <string>com.apple.iwork.pages.template</string>
        </array>
    </dict>
    <dict>
        <key>CFBundleTypeName</key>
        <string>OpenDocument Spreadsheet</string>
        <key>LSHandlerRank</key>
        <string>Alternate</string>
        <key>LSItemContentTypes</key>
        <array>
            <string>org.oasis.opendocument.spreadsheet</string>
        </array>
    </dict>
    <dict>
        <key>CFBundleTypeName</key>
        <string>OpenDocument Presentation</string>
        <key>LSHandlerRank</key>
        <string>Alternate</string>
        <key>LSItemContentTypes</key>
        <array>
            <string>org.oasis.opendocument.presentation</string>
        </array>
    </dict>
    <dict>
        <key>CFBundleTypeName</key>
        <string>OpenDocument Text</string>
        <key>LSHandlerRank</key>
        <string>Alternate</string>
        <key>LSItemContentTypes</key>
        <array>
            <string>org.oasis.opendocument.text</string>
        </array>
    </dict>
    <dict>
        <key>CFBundleTypeName</key>
        <string>Folder</string>
        <key>LSHandlerRank</key>
        <string>Alternate</string>
        <key>LSItemContentTypes</key>
        <array>
            <string>public.folder</string>
        </array>
    </dict>

---

    <dict>
        <key>CFBundleTypeName</key>
        <string>Audio</string>
        <key>LSHandlerRank</key>
        <string>Alternate</string>
        <key>LSItemContentTypes</key>
        <array>
            <string>public.audio</string>
            <string>public.mp3</string>
            <string>public.mpeg-4-audio</string>
            <string>com.apple.protected-​mpeg-4-audio</string>
            <string>public.aifc-audio</string>
            <string>com.apple.coreaudio-​format</string>
            <string>public.aiff-audio</string>
        </array>
    </dict>

---

    <dict>
        <key>CFBundleTypeName</key>
        <string>Movie</string>
        <key>LSHandlerRank</key>
        <string>Alternate</string>
        <key>LSItemContentTypes</key>
        <array>
            <string>public.movie</string>
            <string>public.3gpp2</string>
            <string>public.3gpp</string>
            <string>public.mpeg</string>
            <string>com.apple.quicktime-movie</string>
            <string>public.mpeg-4</string>
        </array>
    </dict>
    <dict>
        <key>CFBundleTypeName</key>
        <string>GIF image</string>
        <key>LSHandlerRank</key>
        <string>Alternate</string>
        <key>LSItemContentTypes</key>
        <array>
            <string>com.compuserve.gif</string>
        </array>
    </dict>
    <dict>
        <key>CFBundleTypeName</key>
        <string>PNG image</string>
        <key>LSHandlerRank</key>
        <string>Alternate</string>
        <key>LSItemContentTypes</key>
        <array>
            <string>public.png</string>
        </array>
    </dict>
    <dict>
        <key>CFBundleTypeName</key>
        <string>TIFF image</string>
        <key>LSHandlerRank</key>
        <string>Alternate</string>
        <key>LSItemContentTypes</key>
        <array>
            <string>public.tiff</string>
        </array>
    </dict>
    <dict>
        <key>CFBundleTypeName</key>
        <string>JPEG image</string>
        <key>LSHandlerRank</key>
        <string>Alternate</string>
        <key>LSItemContentTypes</key>
        <array>
            <string>public.jpeg</string>
        </array>
    </dict>
    <dict>
        <key>CFBundleTypeName</key>
        <string>XML</string>
        <key>LSHandlerRank</key>
        <string>Alternate</string>
        <key>LSItemContentTypes</key>
        <array>
            <string>public.xml</string>
        </array>
    </dict>
    <dict>
        <key>CFBundleTypeName</key>
        <string>HTML</string>
        <key>LSHandlerRank</key>
        <string>Alternate</string>
        <key>LSItemContentTypes</key>
        <array>
            <string>public.html</string>
            <string>public.xhtml</string>
        </array>
    </dict>
    <dict>
        <key>CFBundleTypeName</key>
        <string>Rich Text</string>
        <key>LSHandlerRank</key>
        <string>Alternate</string>
        <key>LSItemContentTypes</key>
        <array>
            <string>public.rtf</string>
            <string>com.apple.rtfd</string>
            <string>com.apple.flat-rtfd</string>
        </array>
    </dict>
    <dict>
        <key>CFBundleTypeName</key>
        <string>Text</string>
        <key>LSHandlerRank</key>
        <string>Alternate</string>
        <key>LSItemContentTypes</key>
        <array>
            <string>public.text</string>
            <string>public.plain-text</string>
            <string>public.utf8-plain-text</string>
            <string>public.utf16-external-plain-​text</string>
            <string>public.utf16-plain-text</string>
            <string>com.apple.traditional-mac-​plain-text</string>
            <string>public.source-code</string>
            <string>public.c-source</string>
            <string>public.objective-c-source</string>
            <string>public.c-plus-plus-source</string>
            <string>public.objective-c-plus-​plus-source</string>
            <string>public.c-header</string>
            <string>public.c-plus-plus-header</string>
            <string>com.sun.java-source</string>
            <string>public.script</string>
            <string>public.shell-script</string>
        </array>
    </dict>
    <dict>
        <key>CFBundleTypeExtensions</key>
        <array>
            <string>zip</string>
            <string>zipx</string>
        </array>
        <key>CFBundleTypeName</key>
        <string>Zip archive</string>
        <key>LSHandlerRank</key>
        <string>Alternate</string>
        <key>LSItemContentTypes</key>
        <array>
            <string>public.zip-archive</string>
            <string>public.archive</string>
            <string>com.pkware.zip-archive</string>
            <string>com.pkware.zipx-archive</string>
        </array>
    </dict>
    <dict>
        <key>CFBundleTypeExtensions</key>
        <array>
            <string>rar</string>
            <string>RAR</string>
        </array>
        <key>CFBundleTypeName</key>
        <string>Rar archive</string>
        <key>LSHandlerRank</key>
        <string>Alternate</string>
        <key>LSItemContentTypes</key>
        <array>
            <string>com.rarlab.rar-archive</string>
            <string>public.archive</string>
        </array>
    </dict>
    <dict>
        <key>CFBundleTypeExtensions</key>
        <array>
            <string>7z</string>
            <string>7Z</string>
        </array>
        <key>CFBundleTypeName</key>
        <string>7z archive</string>
        <key>LSHandlerRank</key>
        <string>Alternate</string>
        <key>LSItemContentTypes</key>
        <array>
            <string>org.7-zip.7-zip-archive</string>
            <string>public.archive</string>
        </array>
    </dict>
    <dict>
        <key>CFBundleTypeName</key>
        <string>Waveform audio</string>
        <key>LSHandlerRank</key>
        <string>Alternate</string>
        <key>LSItemContentTypes</key>
        <array>
            <string>com.microsoft.waveform-​audio</string>
        </array>
    </dict>
    <dict>
        <key>CFBundleTypeName</key>
        <string>Windows icon image</string>
        <key>LSHandlerRank</key>
        <string>Alternate</string>
        <key>LSItemContentTypes</key>
        <array>
            <string>com.microsoft.ico</string>
            <string>com.apple.icns</string>
        </array>
    </dict>
    <dict>
        <key>CFBundleTypeName</key>
        <string>Windows bitmap image</string>
        <key>LSHandlerRank</key>
        <string>Alternate</string>
        <key>LSItemContentTypes</key>
        <array>
            <string>com.microsoft.bmp</string>
        </array>
    </dict>
    <dict>
        <key>CFBundleTypeName</key>
        <string>Microsoft PowerPoint</string>
        <key>LSHandlerRank</key>
        <string>Alternate</string>
        <key>LSItemContentTypes</key>
        <array>
            <string>com.microsoft.powerpoint.​ppt</string>
            <string>org.openxmlformats.presentationml.presentation</string>
        </array>
    </dict>
    <dict>
        <key>CFBundleTypeName</key>
        <string>Microsoft Excel</string>
        <key>LSHandlerRank</key>
        <string>Alternate</string>
        <key>LSItemContentTypes</key>
        <array>
            <string>org.openxmlformats.spreadsheetml.sheet</string>
            <string>com.microsoft.excel.xls</string>
        </array>
    </dict>
    <dict>
        <key>CFBundleTypeName</key>
        <string>Microsoft Word</string>
        <key>LSHandlerRank</key>
        <string>Alternate</string>
        <key>LSItemContentTypes</key>
        <array>
            <string>com.microsoft.word.doc</string>
            <string>com.microsoft.word.wordml</string>
            <string>org.openxmlformats.wordprocessingml.document</string>
        </array>
    </dict>
    <dict>
        <key>CFBundleTypeName</key>
        <string>PDF</string>
        <key>LSHandlerRank</key>
        <string>Alternate</string>
        <key>LSItemContentTypes</key>
        <array>
            <string>com.adobe.pdf</string>
        </array>
    </dict>
</array>

Answer 2

You should use Alternate instead of Alternative

<key>LSHandlerRank</key>
<string>Alternate</string>

Answer 3

<key>CFBundleDocumentTypes</key>
<array>
    <dict>
        <key>CFBundleTypeExtensions</key>
        <array>
            <string>"*"</string>
        </array>
        <key>CFBundleTypeName</key>
        <string>Unknown</string>
        <key>LSItemContentTypes</key>
        <array>
            <string>public.data</string>
        </array>
    </dict>
</array>