I made an application on android and published it on the play store. I signed my apk with a new private key.
Last week, i wanted to update my application with my new features. So I exported my new apk with the same private key previously created. Then I published and playstore accepted it.
But on the play store in my phone, the application cannot be updated. I have to uninstall it before and if I do that, I will lost my data.
So my question is, how can I make an updatable apk on the google play store
You can’t change the signature of your apk uploaded to the play store, you i’ll need to use the same signature as before. If you do change the signature of your app and try to upload it you will get an error telling that the same application was found but with a different signature.
If you manually send your users an app (mail for example) with a changed signature they will have to uninstall the current app before they can install the same app with the new signature. Users will lose there application data doing this! This is a safety mechanism, so hackers/bad people can’t change your apk and get the user data in that way.
The Android system uses the signature to check if the application is really an update for the existing one on your phone. Because only you now your signature password and stuff, hackers can’t use it in there fake app updates for example.
Summary: Always use the same signature!
Check: http://developer.android.com/tools/publishing/app-signing.html
Edit: As said by @HandlerExploit
Probably you have your “non market version/debug version” of the app still installed on your phone, a debug version of the app is always signed with a default debug signature. This signature is different from the one on the market.