I am not sure if this has been mentioned before (I can not find anything on here by searching) but it is worth mentioning again to help others.
I spent ages and vast amounts of time trawling on here thinking that the writeline functions were not working properly when writing to mobiles.
I read in a text file (created on a spreadsheet in csv format) holding all my sprite data and the data on the file was not updating.
In the end I found out that my filename "spritepositions_demo.txt" had an underscore ( _ ) that AppGameKit didn't like.
AGK does not indicate this in anyway (which would have been helpful !) and just ignores the fact and carries on.
So when accessing files on mobiles, stick to all lowercase and no odd characters such as an underscore.
Hope this info helps all you amazing creative peeps out there.
Amazing creations start with a Fuzzy Vision
Dave - Creator, Developer and Visionary
Fuzzy Visions