How to re-sign an existing android app after modifing it

every one . now I am in a project upon android system application source code with the Android v 2.1r1 : Contacts . I have modify the source code and run it on the emulator successfully..

but i get a problem on publishing it to my android phone with the same system version because of without signing it. how can i do if i want to publish it to my android phone after modifying it? do i ne开发者_Go百科ed to resign the Contacts.apk built by mm ? can i just signing the Contacts.apk built by mm? thx for your reading and replies !

You do exactly what the title of your post says. Re-sign the app with your own key. Google isn't about to give you theirs. So you need to create your own key and sign your app with it.

If you don't know how to do this, there are a ton of resources/tutorials/walk throughs already on-line.

I suggest starting here

As user432209 said, you will have to resign the package with your own key. It sounds like you might also be having an issue with your version of Contacts conflicting with the version on your phone. If so, you may need to change the package name.