Ensure that your Activity is not utilizing the:
setContentView(R.layout.activity_main);
It's possible that your layout is empty and that line continues to exist alongside the:
super.loadUrl("file:///android_asset/www/dummy.html");
You can also add a config.xml file in your /res/xml directory (/res/xml/config.xml)
Below is an example of a basic config.xml file:
<?xml version="1.0" encoding="utf-8"?>
<cordova>
<access origin="http://127.0.0.1*"/> <!-- allow local pages -->
<log level="DEBUG"/>
<preference name="useBrowserHistory" value="true" />
<preference name="exit-on-suspend" value="false" />
<plugins>
<plugin name="App" value="org.apache.cordova.App"/>
<plugin name="InAppBrowser" value="org.apache.cordova.InAppBrowser"/>
</plugins>
</cordova>
I encountered similar issues when I initially began working with phonegap.
Also, double-check that the cordova-2.2..jar file is located in your libs folder and properly referenced in your build path.
Hope this information proves helpful.