Value error of type java.lang.String cannot be converted to
means that you probably try to map something like this :
to an array.
So your Json is wrongly formatted, you must have something like this
Since your app works correctly in the emulator, it's probably a
communication error. The error you see is certainly the consequence of
something else. Look at previous logs and log the json string you are
trying to parse. (I'm pretty sure it is not at all what you expect)