Android: Error - App has same packaged different signature

In my case after upgrading Android Studio, I had removed the $HOME/.android folder which made Android Studio create a new $HOME/.android/debug.keystore. After copying the old debug.keystore it worked again.

You can sign your apps with your release key while keeping the debugging option - you just have to add your release key into Android Studio (or specify it on the command line if you are signing your apps there).

In Android Studio, right click on your app in the project browser and open module settings. Select your app's module and click on 'Signing' to make sure your release keystore is listed. Then under 'Build Types', make sure that the debug target and the release target share the same signing config, and that the debug target has debuggable set to true. They should now share the same key.

More information on app signing can be found in the Developer docs here.

I haven't heard of a downside to using the same key for debugging and for release, provided the private key is kept secure (read: not under version control).