Unfortunately, the spark ComboBox doesn't work well at on mobile, because Adobe has not yet optimized it for mobile. There have been a some folks that made their own to work on mobile. I think https://www.flextras.com/ offers an alternative.
In my case, I simply substitute a List when it makes sense.
Thanks for the plug Don,
We don't formally have a Mobile ComboBox; but we do have a Mobile DropDownList and a Mobile AutoComplete component. If you set th FilterFunction to always return true in the AutoComplete, it is very similar to the Spark ComboBox; except without any type ahead 'features'.
We just updated our release builds last night to include two new Mobile DropDownList skins; which display the list in a popup over all controls instead of directly below the prompt area. We also added some new skin parts and properties to support a close button and header. The new skins are more akin to what you'd find on a "normal" mobile device as oppose to our default skin which is what you'd find on the desktop.
I haven't updated the web site demo to include those two new skins yet, though, hopefully that will come before end of this week.
We offer free developer editions, so you can sign up and download them to test out in your own app / mobile device. ( The developer editions are Watermarked )
More info here:
And we're always one click away if you need help. https://www.flextras.com/index.cfm?event=ContactForm