Android java.lang.nullpointerexception hatası

Merhabalar, bir siteden XML parse yapmaktayim fakat aldigim hata dolayisiyla uygulama calismiyor. LogCat uzerinden hatayi aldigim yeri  buldum,arastirdigim kadariyla genelde karsilasilan bir hata...Nasil duzeltebilirim ?

[code]

public class XMLParsing  extends Activity { 

   static final String URL = "http://www.psnit.pl/mobile.xml";

   static final String KEY_ITEM = "item";

    static final String KEY_TITLE = "title";

//static final String KEY_REGION = "region";

    static final String KEY_SNOWCOVER  = "snowCover";

//static final String KEY_SKICONDITIONS = "skiConditions";

    static final String KEY_PUBDATE = "pubDate";

   @Override

    protected void onCreate(Bundle SavedInstanceState) {

        super.onCreate(SavedInstanceState);

        setContentView(R.layout.activity_main);

  ArrayList<HashMap<String, String>> menuItems = new ArrayList<HashMap<String, String>>();

    XMLParsing parser = new XMLParsing();

    String xml = parser.getXmlFromUrl(URL);

            Document doc = parser.getDomElement(xml);

            NodeList nl = doc.getElementsByTagName(KEY_ITEM);  //hatayi aldigim satir burasi

         for (int i=0; i<nl.getLength(); i++) {

        //creating new HashMap

        HashMap <String, String> map = new HashMap<String, String>();

        Element e = (Element) nl.item(i);

        map.put(KEY_TITLE, parser.getValue(e, KEY_TITLE));

//    map.put(KEY_REGION, parser.getValue(e, KEY_REGION));

        map.put(KEY_SNOWCOVER, parser.getValue(e, KEY_SNOWCOVER));

   //   map.put(KEY_SKICONDITIONS, parser.getValue(e, KEY_SKICONDITIONS));

        map.put(KEY_PUBDATE, parser.getValue(e, KEY_PUBDATE));

           menuItems.add(map);

    }

    ListAdapter adapter = new SimpleAdapter(this, menuItems, (Integer) R.layout.list_item, new String[] {KEY_TITLE,KEY_SNOWCOVER,KEY_PUBDATE}, new int[] {

       R.id.title,R.id.snowCover, R.id.pubDate});

        setListAdapter(adapter);

        ListView lv = getListView();

       lv.setOnItemClickListener(new OnItemClickListener() {

         @Override

            public void onItemClick(AdapterView<?> parent, View view,

                    int position, long id) {

                // getting values from selected ListItem

                String title = ((TextView) view.findViewById(R.id.title)).getText().toString();

                String snowCover =((TextView) view.findViewById(R.id.snowCover)).getText().toString();

                String pubDate = ((TextView) view.findViewById(R.id.pubDate)).getText().toString();

                //Starting new Intent

                Intent in = new Intent(XMLParsing.this, SingleMenuItemActivity.class);

                in.putExtra(KEY_TITLE, title);

                in.putExtra(KEY_SNOWCOVER, snowCover);

                in.putExtra(KEY_PUBDATE, pubDate);

                startActivity(in);                

            }

                  });

    }       

[/code]

LogCat 

[code]02-13 15:12:58.568: E/AndroidRuntime(1515): FATAL EXCEPTION: main
02-13 15:12:58.568: E/AndroidRuntime(1515): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.polskiesta.pl/com.polskiesta.pl.XMLParsing}: java.lang.NullPointerException
02-13 15:12:58.568: E/AndroidRuntime(1515):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2180)
02-13 15:12:58.568: E/AndroidRuntime(1515):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)
02-13 15:12:58.568: E/AndroidRuntime(1515):     at android.app.ActivityThread.access$600(ActivityThread.java:141)
02-13 15:12:58.568: E/AndroidRuntime(1515):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
02-13 15:12:58.568: E/AndroidRuntime(1515):     at android.os.Handler.dispatchMessage(Handler.java:99)
02-13 15:12:58.568: E/AndroidRuntime(1515):     at android.os.Looper.loop(Looper.java:137)
02-13 15:12:58.568: E/AndroidRuntime(1515):     at android.app.ActivityThread.main(ActivityThread.java:5041)
02-13 15:12:58.568: E/AndroidRuntime(1515):     at java.lang.reflect.Method.invokeNative(Native Method)
02-13 15:12:58.568: E/AndroidRuntime(1515):     at java.lang.reflect.Method.invoke(Method.java:511)
02-13 15:12:58.568: E/AndroidRuntime(1515):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
02-13 15:12:58.568: E/AndroidRuntime(1515):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
02-13 15:12:58.568: E/AndroidRuntime(1515):     at dalvik.system.NativeStart.main(Native Method)
02-13 15:12:58.568: E/AndroidRuntime(1515): Caused by: java.lang.NullPointerException
02-13 15:12:58.568: E/AndroidRuntime(1515):     at com.polskiesta.pl.XMLParsing.onCreate(XMLParsing.java:48)
02-13 15:12:58.568: E/AndroidRuntime(1515):     at android.app.Activity.performCreate(Activity.java:5104)
02-13 15:12:58.568: E/AndroidRuntime(1515):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080)
02-13 15:12:58.568: E/AndroidRuntime(1515):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2144)
02-13 15:12:58.568: E/AndroidRuntime(1515):     ... 11 more

[/code]