Cannot uninstall old OS installed application and upgrade to a new version on Android

What is the easiest way to upgrade an application that was installed on the OS? I cannot delete this application from Setting->Application List - "Uninstall" option is unselectable.

BTW: I have changed a few things on androidmanifest.xml, like added more activities, changed the st开发者_开发问答art up(launch/main) activity. The package is the same. I have updated version name and code.

When I try to download a new version of the application, the OS installs TWO applications with the same name. Of course I want the previous to be replaced by the new one.

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Have you tried uninstalling it through adb?

You'll need to connect your device to your computer via the USB cable and try this:

adb uninstall your.package

This is all assuming that you have the Android SDK installed and updated with the tools (adb).

And here is some more info on adb:

http://developer.android.com/guide/developing/tools/adb.html

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You can delete the app in Command Prompt (Windows) or Terminal (OSX/Linux) with the command: adb uninstall com.packagename.package from your phone/simulator. Be sure to have 1 phone or 1 simulator open at the moment you execute this code.

Here is some more info about the ADB: http://developer.android.com/guide/developing/tools/adb.html