cordova-2.9.1.jar Breaks My App

Question

I have a PhoneGap App and I am trying to add DroidGap:

import org.apache.cordova.DroidGap;
public class RestartAppActivity extends DroidGap {
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        super.loadUrl("file:///android_asset/www/index.html");
    }
}

I also added cordova-2.9.1.jar to the libs folder. But now when I run the app MainActivity will not start. The error is L java.lang.NoSuchFieldError: No field launchUrl of type Ljava/lang/String MainActivity:

public class MainActivity extends CordovaActivity
{
    @Override
    public void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        loadUrl(launchUrl);
    }
}

Thanks!