Demo Version of Application

Question

What is the recommended way of creating a demo version for an application. Basically, the demo version will be fully functional, but will be limited to running it 25 times. My worry is that if the user uninstalls and reinstalls, the count will be reset.

I thought about writing a data file to the SD Card with the count of executions (hoping that would persist after uninstall), but I do not want to add that permission if I can avoid it.

Any suggestions on how to have some type of demo flag persist after an uninstall?

Answer 1

Even if it's on the SD card, there's no reason the user can't just go and delete your file themselves.

I asked a similar question a few months ago, but that was for a review copy, not a demo version. You could do something similar to what Dave Webb suggested and store each user's device id on a server. It would mean you'd both need the READ_PHONE_STATE and INTERNET permissions enabled and I can understand not wanting to add additional permissions. However, it is the only fool-proof way I can think of to guarantee that an application is only run X number of times, as any change you make to the phone can be reversed.

mbaird pointed out that anyone can install the full version of your app and try it for one day before requesting a refund; with this in mind you might make a crippled demo version that informs the user of this (not-oft-used) Market functionality.