android signing problem while doing auto update

I 开发者_如何学Chave created a application and released it with out signing it. also i have updated my application few times after the first release.

After few months , now would like to give a another update. if i install my application in mobile , its not getting install, its installed only after i uninstalled the existing application from the mobile.

in console its showing , "Change in application signature"

I know i made a mistake by not signing the application with private key at first time. But please any one tell me How my default debug key has changed now.. so that i can roll back.

is there any way to solve the issue? or i should ask my users to uninstall the app.

Thanks.

Several things can cause the debug key to change, such as reinstalling the SDK or building the APK from a different system. The only way to upload a new version of your app now is to delete the old one and upload the new one, e.g. adb uninstall com.example.appPackageName first.