How to build an app with an existing apk signature

Question

I compiled a project (that contains a sqlite db) using a pc that I have not access to that no more. People used that and inserted records to the db. I don't have any access to their tablets. I made a mistake and i have sent them the apk was in bin directory. I changed the program, I want to tell them to update their apps but when they try to replace app, android doesn't let them. So i have to sign my apk as same as the signature of the apk i made on that computer. What should i do ? Thanks for your help.

Answer 1

Expanding on my comments:

There's not much you can really do if you don't have access to the old signature. It sounds like you're talking about the debug signature. As you found out, this varies from machine to machine, and if you don't have access to the old machine, it's just gone.

This is normally a good thing for security reasons. If it was possible to recover your key, anyone could do it. Then they could maliciously modify the app and upload it as a replacement.

As you've also found out, Android won't let you install an update that has a different signature than the currently installed version. If your users completely uninstall the app, they will then be able to install the new one. That's definitely inconvenient, and a customer service headache, but there's not any other way to do it.

Note that the users will lose any databases, etc, that they had in the app. It will act as a fresh install, since that's what it is.

Theoretically, rooted users could back up their old databases/preferences with any number of utilities and restore them later. In practice, even most users that can do this won't bother with it.