Application to combat the city airship

I had a problem trying to integrate PUSH notifications from Urban Airship into an Android app.

I think I have all my permission and intent filters in AndroidManifest, but the application will work right after trying to set my AirshipConfigOptions as follows:

public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);

    AirshipConfigOptions options = AirshipConfigOptions.loadDefaultOptions(this);
    ...
}

My error log says:

java.lang.NoClassDefFoundError: com.urbanairship.AirshipConfigOptions

Any help would be greatly appreciated.