Android: saving info for trial application

I want to save some info regarding a trial version an application.

I want this info to be 开发者_StackOverflow社区persistent in order to detect if the user removed the application and installed it again after the trial expiry.

what is the best place to store such info

thanks

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Most of the times the solution to this problem is to keep an server side check,

But if you dont want to involve a server its better to give some limited functionality in your trail app and full in the paid version.

There are other methods too like Time Trial but again they all depends on persistent data so they also fails if the user uninstalls and installs again your applucation

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Store it in external file.

it wont be deleted after user uninstalled the app.

but

Serverside check by Device ID is the good way ..

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I'm working on the same "problem" at the moment (offline solution for trial time expired apps):

My findings: There is no way to ensure that a user never can reinstall & reuse a (time) trial app but there is a way to 'nearly' prevent it:

1. Use shared preferences / a database / file saved on internal storage containing the install timestamp.
2. If the device has an external storage card (most devices have) also save the timestamp on the sd card.

The only possiblity to use your application also after expiring is if the user 1. clears app data on the phone and 2. finds the timestamp file on the sd card and also kills this one.

If he "just kills" the first or second check the killed one can be restored on next app start.