Best place/area to store file for Trail period

Question

I need to have a trial period (7 days) in my application. From this I came to know that you can do that by keeping permanent file, database or shared preference.

Where do I keep that file so that the user isn't able to see/delete it.

If I put that logic in Sharedpreference or a file with a path "data/data/packagename", when the application is uninstalled then all history will be lost.

Any other workaround/ideas?

Note: there is no server, application works locally with no Internet.

Answer 1

You can store as hidden so no chance to delete by user

see this

Answer 2

I would say a better workaround would be encrypt your file and then store it in a random place. This way, even if the user has the access to that file, he/she is least likely to tell it's purpose and delete it anyway. And Android has great support for encryption as well.

Have a look at these to get you started:

Android Crypto Implementation

Android Developer: Crypto Package Summary

Answer 3

I would say, make the application's data which can't be cleared from manifest like this:

android:manageSpaceActivity="YourStartingActivity" 

in application tag.

Now place the application in database or application folder. This solution will save you from clearing application data. Now for uninstallation issue. Make a broad cast receiver which triggers when any application is uninstalled from the device. Once user will try uninstall your application you can catch it through receiver and prevent it. This broadcast receiver can be in a separate class like Watcher class which will be installed with your application. You can do it easily. There are many examples.