Question

here i am just trying to parse an xml file and store the contents in an array lists, but everytime its giving java.Lang.NullPointerException at two points, pls help in debugging this…

public class XML_PARSER extends Activity {

String TAG= "XML_PARSER";
List optionList = new ArrayList(); 
Document dom;

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.parser);



    Document doc=parseXmlFile();

at this line it is giving a java null pointer exception

    ParseDocument(doc); 

    //printData();


}
private Document parseXmlFile(){
    DocumentBuilderFactory dbf= DocumentBuilderFactory.newInstance();

    try {
        DocumentBuilder db = dbf.newDocumentBuilder();
        dom=db.parse("R.raw.options.xml");

    }

    catch(ParserConfigurationException pce){
        pce.printStackTrace();
    }
    catch(SAXException se){
        se.printStackTrace();
    }
    catch(IOException ioe){
        ioe.printStackTrace();
    }
    return dom;

}


private void ParseDocument(Document dom){

at this lineits giving the same error

    Element docEle = dom.getDocumentElement();
    Node node;

    NodeList n1= docEle.getElementsByTagName("Option");
    if(n1!=null && n1.getLength()>0){
        for(int i=0;i<n1.getLength();i++){
            node=n1.item(i);

            Element e1=(Element)n1.item(i);

            Option e = getOption(e1,node);

            optionList.add(e);

            }

        }
    }

here is the log cat for the same

07-20 12:21:48.391: E/AndroidRuntime(836): Caused by: java.lang.NullPointerException
07-20 12:21:48.391: E/AndroidRuntime(836):  at com.example.xml_parser.XML_PARSER.ParseDocument(XML_PARSER.java:67)

07-20 12:21:48.391: E/AndroidRuntime(836):  at com.example.xml_parser.XML_PARSER.onCreate(XML_PARSER.java:38)

07-20 12:21:48.391: E/AndroidRuntime(836):  at android.app.Activity.performCreate(Activity.java:5008)

07-20 12:21:48.391: E/AndroidRuntime(836):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1079)

07-20 12:21:48.391: E/AndroidRuntime(836):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2023)

Answer 1

The problem is that R.raw.options.xml is not a valid URI so in this line dom=db.parse("R.raw.options.xml");, the dom variable is null. You are trying to use methods of the null variable doc (line Element docEle = dom.getDocumentElement(); inside the ParseDocument(doc); method), that is why you get a NullPointerException. If you pass a valid URI in dom=db.parse("valid_URI"); method you will eliminate the twoNullPointerExceptions.

EDIT Here is a complete example:

private Document parseXmlFile(){
    DocumentBuilderFactory dbf= DocumentBuilderFactory.newInstance();

    try {
       DocumentBuilder db = dbf.newDocumentBuilder();
       Resources res = getResources();
       InputStream in = res.openRawResource(R.raw.options);
       dom=db.parse(in); //Here instead of passing the URI string, you pass the input stream of the file.

    }

    catch(ParserConfigurationException pce){
        pce.printStackTrace();
    }
    catch(SAXException se){
        se.printStackTrace();
    }
    catch(IOException ioe){
        ioe.printStackTrace();
    }
    return dom;

}

Hope that helps.