I am going to make a huge update in an app. It will connect to a new DB using new APIs, I will renew all the layouts, add some functionalities, remove others... so I am thinking on starting it from scratch because I will spend more time updating the old project than creating a new one.
The problem is that when I finish it I want to put it in google play instead of the old one and for that the fingerprint must match. So I need to create a new apk but with the fingerprint of the old one. Is that possible? Or otherwise is there a way to update a google play app with an apk with different apk?
If you have the keystore file that you used to sign the old app, the you just need to copy it to your new project and follow these instructions to sign your new apk with the old certificate.
Also, take into account that the package name of the new app must be the same you used in the old one.
Take a look at this blog post: Things That Cannot Change