Here is a dump (with some details clipped out) of the view hierarchy of a mail composer on iPhone.
<UILayoutContainerView>
| <UINavigationTransitionView>
| | <UIViewControllerWrapperView>
| | | <MFMailComposeView>
| | | | <UIView>
| | | | | <MFComposeScrollView>
| | | | | | <UIView>
| | | | | | | <_MFComposeRecipientView>
| | | | | | | | <UIView>
| | | | | | | | <MFRecipientTextField>
| | | | | | | | <MFHeaderLabelView>
| | | | | | | <MFComposeMultiView>
| | | | | | | | <UIView>
| | | | | | | | <MFHeaderLabelView>
| | | | | | | | <UILabel>
| | | | | | | <MFComposeSubjectView>
| | | | | | | | <UIView>
| | | | | | | | <MFHeaderLabelView>
| | | | | | | | <UITextField>
| | | | | | | | | <UITextFieldLabel>
| | | | | | <MFComposeTextContentView>
| | | | | | | <MFComposeBodyField>
| | | | | | <UIImageView>
| | | | | | <UIImageView>
| <UINavigationBar>
| | <UINavigationItemView>
| | <UINavigationButton>
| | | <UIImageView>
| | | <UIButtonLabel>
| | <UINavigationButton>
| | | <UIImageView>
| | | <UIButtonLabel>
You will find that all of the MFCompose___View
s are not documented. This means they are off limits. As far as I've seen, there is no such control available in iOS 4.
I don't recommend Three20 just to use one element. It substantially increases compile time, and I've found several bugs with Three20. It's good, but could be much better.
I would highly recommend checking out Cocoa Controls, if you haven't already. You might find what you want there. Github is also another great source.
If you do end up using TTPickerTextField
and find that it's buggy, you can always rewrite the code from scratch or fix the bug in the source code.
EDIT:
I found a control via Cocoa Controls that should do what you want. You can find it on Github. It's called TITokenFieldView.
Here's another one on Github called JSTokenField.
I've never used either token field, so I can't vouch for their quality.