I have my students submit their .aia file to Google Classroom and then I run the app on my computer to grade it. Students have started to figure out they can also email the .aia files to each other and essentially they are turning in other students' work as their own. Is there anyway to see when a file was created or who created the file? Trying to figure out some way in the future I can check to see if a student did their own work or used someone elses file.
If the aia file is only copied and sent to the school, you can check the google account under which it was created. But if the second student imported the project into their account and then exported the new aia file, then it is unlikely that the fraud can be recognized.
Yes the second student is importing and saving a new version of the file and then exporting.
The nature of programming is that you should expect similar solutions to homework assignments.
Two aia files can be compared by downloading an image of the Blocks of each project that is sent to you.
If the images of the Blocks from two are 'identical', there is a possibility of sharing / copying files. A way to avoid plagiarism is to query students about how certain parts of a Project work as part of the assignment.
Right I can compare and probably figure if they cheated, but I can't say for sure because their code should be similar.
The file size of the .aia file changes when it is imported and exported, true.
But you can catch total laziness by comparing .aia file sizes in the aggregate, if you bother to enter them into a spreadsheet and sort by size. A match means you have a student who never opened the .aia he got from his friend.
Hi, new to the group, and this is exactly what I came for. Has there been any update on how to catch my students sharing files? They work on Chromebooks, download the .aia files from www.mypltw.org, then upload them to MIT App Inventor. Is there anything in the code that would show that it was from someone else?
Thank you in advance.
In my opinion NO.
One way to tell if a student is copying code rather than learning to code is to ask a student to explain why they did what they did. If they cannot they might have copied code (or they forgot 
Don't just request a solution, request the student's provide comments in the code.
But who cares, part of learning to code is to copy code. We learn by mimicking the thought process of others. 
most of the best coders here on the forum do that!
Thanks SteveJG. Normally, I get it, even I go into google to get things I need to help out here and there. This situation is a student who hasn't done anything all quarter, and will magically have everything done on the last day. Just want definitive proof when I have to call the parents. Thank you though, I'll be comparing their codes to their partners!