Android Question Unlock app

[Fabri]

How can I enter an unlock code so that the user can use the application?
I will arrange the distribution of my app by email, but I want the application to be used only with my authorization.
The unlock code must be different for each device, I had thought about connecting it to the IMEI + date..
Thanks

 

[Erel]

There are many possible solutions.

For example you can use FirebaseAuth to authenticate the user and then send the user email to your server to authorize it.

Getting a unique id is not so simple and will not be 100% reliable. See this thread: https://www.b4x.com/android/forum/t...ique-id-alternative-to-phoneid.14759/#content
It will also mean that the user need to send you the value before you send back the code.