Null Pointer Exception: setinput function for Xmlpullparser assigning null value with StringReader

Question

I'm having a problem where the parser is assigning a null value but when the object field is checked (feed variable) it is not null. Code below. Any help is appreciated.

line causing the error is: xpp.setInput( new StringReader ( mwordItem.getFeed()) );

package com.example.wffd;

import android.os.Bundle;
import android.os.AsyncTask;
import android.app.Activity;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import android.view.Menu;

import java.io.BufferedInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.StringReader;

import java.net.URL;
import java.net.HttpURLConnection;
import org.xmlpull.v1.XmlPullParser;
import org.xmlpull.v1.XmlPullParserException;
import org.xmlpull.v1.XmlPullParserFactory;




public class WffdhomeActivity extends Activity {

    Button updateButton;
    TextView wdTextView, cwTextView;
    WordItem myWordItem ;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_wffdhome);
        updateButton = (Button)findViewById(R.id.button1);
        wdTextView = (TextView)findViewById(R.id.textView2);
        cwTextView = (TextView)findViewById(R.id.textView3);
        myWordItem= new WordItem();


        updateButton.setOnClickListener(new View.OnClickListener() {
      public void onClick(View view) {
        try {
            URL url = new URL("http://www.dictionary.reference.com/wordoftheday/wotd.rss");
            HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();

            new FeedGrab(myWordItem).execute(urlConnection);
            update_screen(myWordItem);

            cwTextView.setText(myWordItem.getWord());
            wdTextView.setText(myWordItem.getDefinition());
        } catch (XmlPullParserException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
      }
      });

    }

    private class FeedGrab extends AsyncTask<HttpURLConnection,Void,Boolean>{

        WordItem aWordItem;

        public FeedGrab( WordItem mWordItem){

            this.aWordItem=mWordItem;
        }

        protected Boolean doInBackground(HttpURLConnection... urls) {
            try {
                InputStream in = new BufferedInputStream(urls[0].getInputStream());
                aWordItem.setFeed(readStream(in));

            }
            catch(IOException e)
            {
                e.printStackTrace();
            }
            finally {

               urls[0].disconnect();
           }
            return true;
        }

         private String readStream(InputStream is) throws IOException {
                StringBuilder sb = new StringBuilder();  
                BufferedReader r = new BufferedReader(new InputStreamReader(is),1000);  
                for (String line = r.readLine(); line != null; line =r.readLine()){  
                    sb.append(line);  
                }  
                is.close();  
                return sb.toString();
            }


    }
    public void update_screen( WordItem mwordItem)throws XmlPullParserException, IOException
    {
         XmlPullParserFactory factory = XmlPullParserFactory.newInstance();
         factory.setNamespaceAware(true); 
         XmlPullParser xpp = factory.newPullParser();
         xpp.setInput( new StringReader ( mwordItem.getFeed()) );


         int eventType = xpp.getEventType();
         String tag_id="item";
         boolean in_item = false,in_description = false;

         String tag_def="description";



         while (eventType != XmlPullParser.END_DOCUMENT) {

        if((eventType == XmlPullParser.START_TAG) )
          {
            if(tag_id.equalsIgnoreCase(xpp.getName()))  
                    {
                        in_item = true;
                    }else if(tag_def.equalsIgnoreCase(xpp.getName()))
                    {
                        in_description= true;
                    }


          } else if(eventType == XmlPullParser.END_TAG) {
              System.out.println("End tag "+xpp.getName());

          } else if((eventType == XmlPullParser.TEXT ) &&(in_description & in_item)) {
              mwordItem.processString(xpp.getText());
              in_description=false;
              in_item = false;
          }
          eventType = xpp.next();
         }
         System.out.println("End document");
     }


    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.wffdhome, menu);
        return true;
    }




}

WordItemClass:

package com.example.wffd;

public class WordItem {
    private String word;
    private String definition;
    private String feed;

    public String getFeed() {
        return feed;
    }
    public void setFeed(String feed) {
        this.feed = feed;
    }

    public String getWord() {
        return word;
    }
    public void setWord(String word) {
        this.word = word;
    }
    public String getDefinition() {
        return definition;
    }
    public void setDefinition(String definition) {
        this.definition = definition;
    }
    public void processString(String text){
        String[] phrase = text.split(":");
    this.setWord(phrase[0]);
    this.setDefinition(phrase[1]);

    }


}

EDIT: Not sure if this is the stack trace.. but here:

Thread [<1> main] (Suspended (exception NullPointerException))  
    <VM does not provide monitor information>   
    WffdhomeActivity.update_screen(WordItem) line: 110  
    WffdhomeActivity$1.onClick(View) line: 51   
    Button(View).performClick() line: 4204  
    View$PerformClick.run() line: 17355 
    Handler.handleCallback(Message) line: 725   
    ViewRootImpl$ViewRootHandler(Handler).dispatchMessage(Message) line: 92 
    Looper.loop() line: 137 
    ActivityThread.main(String[]) line: 5041    
    Method.invokeNative(Object, Object[], Class, Class[], Class, int, boolean) line: not available [native method]  
    Method.invoke(Object, Object...) line: 511  
    ZygoteInit$MethodAndArgsCaller.run() line: 793  
    ZygoteInit.main(String[]) line: 560 

**Update: Using debugger mwordItem.getfeed() is returning null yet feed string contains data. Not sure what's going on here

**Update @andy256:I thought using aWordItem as a reference to myWordItem and modifying the feed variable I had solved that problem Apparently that's not what I did. How do I pass the value from the async thread? I tried passing the value through onpostexecute with no success.

protected void onPostExecute(WordItem result) {

        this.aWordItem=result;
        return;
    }

Answer 1

The stack trace shows

WffdhomeActivity.update_screen(WordItem) line: 110
WffdhomeActivity$1.onClick(View) line: 51

So something on line 110 is null:

xpp.setInput( new StringReader ( mwordItem.getFeed()) );

Since xpp seems to be set, look at mwordItem. It comes from the call at line 51, where myWordItem is passed. In the code posted, myWordItem is never set.

So, from the code you have posted: myWordItem is null.