samples/RSSReader/src/com/example/android/rssreader/RssReader.java - platform/development - Git at Google

 /*
  * Copyright (C) 2007 The Android Open Source Project
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
  *
  *      http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */

 package com.example.android.rssreader;

 import org.xmlpull.v1.XmlPullParser;
 import org.xmlpull.v1.XmlPullParserException;

 import android.app.ListActivity;
 import android.content.Context;
 import android.content.Intent;
 import android.net.Uri;
 import android.os.Bundle;
 import android.os.Handler;
 import android.view.Menu;
 import android.view.MenuItem;
 import android.view.View;
 import android.view.View.OnClickListener;
 import android.view.ViewGroup;
 import android.view.LayoutInflater;
 import android.widget.ArrayAdapter;
 import android.widget.Button;
 import android.widget.EditText;
 import android.widget.ListView;
 import android.widget.TextView;
 import android.widget.TwoLineListItem;
 import android.util.Xml;

 import java.io.IOException;
 import java.io.InputStream;
 import java.net.URL;
 import java.net.URLConnection;
 import java.util.ArrayList;
 import java.util.List;

 /**
  * The RssReader example demonstrates forking off a thread to download
  * rss data in the background and post the results to a ListView in the UI.
  * It also shows how to display custom data in a ListView
  * with a ArrayAdapter subclass.
  *
  * <ul>
  * <li>We own a ListView
  * <li>The ListView uses our custom RSSListAdapter which
  * <ul>
  * <li>The adapter feeds data to the ListView
  * <li>Override of getView() in the adapter provides the display view
  * used for selected list items
  * </ul>
  * <li>Override of onListItemClick() creates an intent to open the url for that
  * RssItem in the browser.
  * <li>Download = fork off a worker thread
  * <li>The worker thread opens a network connection for the rss data
  * <li>Uses XmlPullParser to extract the rss item data
  * <li>Uses mHandler.post() to send new RssItems to the UI
  * <li>Supports onSaveInstanceState()/onRestoreInstanceState() to save list/selection state on app
  * pause, so can resume seamlessly
  * </ul>
  */
 public class RssReader extends ListActivity {
     /**
      * Custom list adapter that fits our rss data into the list.
      */
     private RSSListAdapter mAdapter;

     /**
      * Url edit text field.
      */
     private EditText mUrlText;

     /**
      * Status text field.
      */
     private TextView mStatusText;

     /**
      * Handler used to post runnables to the UI thread.
      */
     private Handler mHandler;

     /**
      * Currently running background network thread.
      */
     private RSSWorker mWorker;

     // Take this many chars from the front of the description.
     public static final int SNIPPET_LENGTH = 90;


     // Keys used for data in the onSaveInstanceState() Map.
     public static final String STRINGS_KEY = "strings";

     public static final String SELECTION_KEY = "selection";

     public static final String URL_KEY = "url";

     public static final String STATUS_KEY = "status";

     /**
      * Called when the activity starts up. Do activity initialization
      * here, not in a constructor.
      *
      * @see Activity#onCreate
      */
     @Override
     protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);

         setContentView(R.layout.rss_layout);
         // The above layout contains a list id "android:list"
         // which ListActivity adopts as its list -- we can
         // access it with getListView().

         // Install our custom RSSListAdapter.
         List<RssItem> items = new ArrayList<RssItem>();
         mAdapter = new RSSListAdapter(this, items);
         getListView().setAdapter(mAdapter);

         // Get pointers to the UI elements in the rss_layout
         mUrlText = (EditText)findViewById(R.id.urltext);
         mStatusText = (TextView)findViewById(R.id.statustext);

         Button download = (Button)findViewById(R.id.download);
         download.setOnClickListener(new OnClickListener() {
             public void onClick(View v) {
                 doRSS(mUrlText.getText());
             }
         });

         // Need one of these to post things back to the UI thread.
         mHandler = new Handler();

         // NOTE: this could use the icicle as done in
         // onRestoreInstanceState().
     }

     /**
      * ArrayAdapter encapsulates a java.util.List of T, for presentation in a
      * ListView. This subclass specializes it to hold RssItems and display
      * their title/description data in a TwoLineListItem.
      */
     private class RSSListAdapter extends ArrayAdapter<RssItem> {
         private LayoutInflater mInflater;

         public RSSListAdapter(Context context, List<RssItem> objects) {
             super(context, 0, objects);

             mInflater = (LayoutInflater)context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
         }

         /**
          * This is called to render a particular item for the on screen list.
          * Uses an off-the-shelf TwoLineListItem view, which contains text1 and
          * text2 TextViews. We pull data from the RssItem and set it into the
          * view. The convertView is the view from a previous getView(), so
          * we can re-use it.
          *
          * @see ArrayAdapter#getView
          */
         @Override
         public View getView(int position, View convertView, ViewGroup parent) {
             TwoLineListItem view;

             // Here view may be passed in for re-use, or we make a new one.
             if (convertView == null) {
                 view = (TwoLineListItem) mInflater.inflate(android.R.layout.simple_list_item_2,
                         null);
             } else {
                 view = (TwoLineListItem) convertView;
             }

             RssItem item = this.getItem(position);

             // Set the item title and description into the view.
             // This example does not render real HTML, so as a hack to make
             // the description look better, we strip out the
             // tags and take just the first SNIPPET_LENGTH chars.
             view.getText1().setText(item.getTitle());
             String descr = item.getDescription().toString();
             descr = removeTags(descr);
             view.getText2().setText(descr.substring(0, Math.min(descr.length(), SNIPPET_LENGTH)));
             return view;
         }

     }

     /**
      * Simple code to strip out <tag>s -- primitive way to sortof display HTML as
      * plain text.
      */
     public String removeTags(String str) {
         str = str.replaceAll("<.*?>", " ");
         str = str.replaceAll("\\s+", " ");
         return str;
     }

     /**
      * Called when user clicks an item in the list. Starts an activity to
      * open the url for that item.
      */
     @Override
     protected void onListItemClick(ListView l, View v, int position, long id) {
         RssItem item = mAdapter.getItem(position);

         // Creates and starts an intent to open the item.link url.
         Intent intent = new Intent(Intent.ACTION_VIEW, Uri.parse(item.getLink().toString()));
         startActivity(intent);
     }

     /**
      * Resets the output UI -- list and status text empty.
      */
     public void resetUI() {
         // Reset the list to be empty.
         List<RssItem> items = new ArrayList<RssItem>();
         mAdapter = new RSSListAdapter(this, items);
         getListView().setAdapter(mAdapter);

         mStatusText.setText("");
         mUrlText.requestFocus();
     }

     /**
      * Sets the currently active running worker. Interrupts any earlier worker,
      * so we only have one at a time.
      *
      * @param worker the new worker
      */
     public synchronized void setCurrentWorker(RSSWorker worker) {
         if (mWorker != null) mWorker.interrupt();
         mWorker = worker;
     }

     /**
      * Is the given worker the currently active one.
      *
      * @param worker
      * @return
      */
     public synchronized boolean isCurrentWorker(RSSWorker worker) {
         return (mWorker == worker);
     }

     /**
      * Given an rss url string, starts the rss-download-thread going.
      *
      * @param rssUrl
      */
     private void doRSS(CharSequence rssUrl) {
         RSSWorker worker = new RSSWorker(rssUrl);
         setCurrentWorker(worker);

         resetUI();
         mStatusText.setText("Downloading\u2026");

         worker.start();
     }

     /**
      * Runnable that the worker thread uses to post RssItems to the
      * UI via mHandler.post
      */
     private class ItemAdder implements Runnable {
         RssItem mItem;

         ItemAdder(RssItem item) {
             mItem = item;
         }

         public void run() {
             mAdapter.add(mItem);
         }

         // NOTE: Performance idea -- would be more efficient to have he option
         // to add multiple items at once, so you get less "update storm" in the UI
         // compared to adding things one at a time.
     }

     /**
      * Worker thread takes in an rss url string, downloads its data, parses
      * out the rss items, and communicates them back to the UI as they are read.
      */
     private class RSSWorker extends Thread {
         private CharSequence mUrl;

         public RSSWorker(CharSequence url) {
             mUrl = url;
         }

         @Override
         public void run() {
             String status = "";
             try {
                 // Standard code to make an HTTP connection.
                 URL url = new URL(mUrl.toString());
                 URLConnection connection = url.openConnection();
                 connection.setConnectTimeout(10000);

                 connection.connect();
                 InputStream in = connection.getInputStream();

                 parseRSS(in, mAdapter);
                 status = "done";
             } catch (Exception e) {
                 status = "failed:" + e.getMessage();
             }

             // Send status to UI (unless a newer worker has started)
             // To communicate back to the UI from a worker thread,
             // pass a Runnable to handler.post().
             final String temp = status;
             if (isCurrentWorker(this)) {
                 mHandler.post(new Runnable() {
                     public void run() {
                         mStatusText.setText(temp);
                     }
                 });
             }
         }
     }

     /**
      * Populates the menu.
      */
     @Override
     public boolean onCreateOptionsMenu(Menu menu) {
         super.onCreateOptionsMenu(menu);

         menu.add(0, 0, 0, "Slashdot")
             .setOnMenuItemClickListener(new RSSMenu("http://rss.slashdot.org/Slashdot/slashdot"));

         menu.add(0, 0, 0, "Google News")
             .setOnMenuItemClickListener(new RSSMenu("http://news.google.com/?output=rss"));

         menu.add(0, 0, 0, "News.com")
             .setOnMenuItemClickListener(new RSSMenu("http://news.com.com/2547-1_3-0-20.xml"));

         menu.add(0, 0, 0, "Bad Url")
             .setOnMenuItemClickListener(new RSSMenu("http://nifty.stanford.edu:8080"));

         menu.add(0, 0, 0, "Reset")
                 .setOnMenuItemClickListener(new MenuItem.OnMenuItemClickListener() {
             public boolean onMenuItemClick(MenuItem item) {
                 resetUI();
                 return true;
             }
         });

         return true;
     }

     /**
      * Puts text in the url text field and gives it focus. Used to make a Runnable
      * for each menu item. This way, one inner class works for all items vs. an
      * anonymous inner class for each menu item.
      */
     private class RSSMenu implements MenuItem.OnMenuItemClickListener {
         private CharSequence mUrl;

         RSSMenu(CharSequence url) {
             mUrl = url;
         }

         public boolean onMenuItemClick(MenuItem item) {
             mUrlText.setText(mUrl);
             mUrlText.requestFocus();
             return true;
         }
     }


     /**
      * Called for us to save out our current state before we are paused,
      * such a for example if the user switches to another app and memory
      * gets scarce. The given outState is a Bundle to which we can save
      * objects, such as Strings, Integers or lists of Strings. In this case, we
      * save out the list of currently downloaded rss data, (so we don't have to
      * re-do all the networking just because the user goes back and forth
      * between aps) which item is currently selected, and the data for the text views.
      * In onRestoreInstanceState() we look at the map to reconstruct the run-state of the
      * application, so returning to the activity looks seamlessly correct.
      * TODO: the Activity javadoc should give more detail about what sort of
      * data can go in the outState map.
      *
      * @see android.app.Activity#onSaveInstanceState
      */
     @SuppressWarnings("unchecked")
     @Override
     protected void onSaveInstanceState(Bundle outState) {
         super.onSaveInstanceState(outState);

         // Make a List of all the RssItem data for saving
         // NOTE: there may be a way to save the RSSItems directly,
         // rather than their string data.
         int count = mAdapter.getCount();

         // Save out the items as a flat list of CharSequence objects --
         // title0, link0, descr0, title1, link1, ...
         ArrayList<CharSequence> strings = new ArrayList<CharSequence>();
         for (int i = 0; i < count; i++) {
             RssItem item = mAdapter.getItem(i);
             strings.add(item.getTitle());
             strings.add(item.getLink());
             strings.add(item.getDescription());
         }
         outState.putSerializable(STRINGS_KEY, strings);

         // Save current selection index (if focussed)
         if (getListView().hasFocus()) {
             outState.putInt(SELECTION_KEY, Integer.valueOf(getListView().getSelectedItemPosition()));
         }

         // Save url
         outState.putString(URL_KEY, mUrlText.getText().toString());

         // Save status
         outState.putCharSequence(STATUS_KEY, mStatusText.getText());
     }

     /**
      * Called to "thaw" re-animate the app from a previous onSaveInstanceState().
      *
      * @see android.app.Activity#onRestoreInstanceState
      */
     @SuppressWarnings("unchecked")
     @Override
     protected void onRestoreInstanceState(Bundle state) {
         super.onRestoreInstanceState(state);

         // Note: null is a legal value for onRestoreInstanceState.
         if (state == null) return;

         // Restore items from the big list of CharSequence objects
         List<CharSequence> strings = (ArrayList<CharSequence>)state.getSerializable(STRINGS_KEY);
         List<RssItem> items = new ArrayList<RssItem>();
         for (int i = 0; i < strings.size(); i += 3) {
             items.add(new RssItem(strings.get(i), strings.get(i + 1), strings.get(i + 2)));
         }

         // Reset the list view to show this data.
         mAdapter = new RSSListAdapter(this, items);
         getListView().setAdapter(mAdapter);

         // Restore selection
         if (state.containsKey(SELECTION_KEY)) {
             getListView().requestFocus(View.FOCUS_FORWARD);
             // todo: is above right? needed it to work
             getListView().setSelection(state.getInt(SELECTION_KEY));
         }

         // Restore url
         mUrlText.setText(state.getCharSequence(URL_KEY));

         // Restore status
         mStatusText.setText(state.getCharSequence(STATUS_KEY));
     }


     /**
      * Does rudimentary RSS parsing on the given stream and posts rss items to
      * the UI as they are found. Uses Android's XmlPullParser facility. This is
      * not a production quality RSS parser -- it just does a basic job of it.
      *
      * @param in stream to read
      * @param adapter adapter for ui events
      */
     void parseRSS(InputStream in, RSSListAdapter adapter) throws IOException,
             XmlPullParserException {
         // TODO: switch to sax

         XmlPullParser xpp = Xml.newPullParser();
         xpp.setInput(in, null);  // null = default to UTF-8

         int eventType;
         String title = "";
         String link = "";
         String description = "";
         eventType = xpp.getEventType();
         while (eventType != XmlPullParser.END_DOCUMENT) {
             if (eventType == XmlPullParser.START_TAG) {
                 String tag = xpp.getName();
                 if (tag.equals("item")) {
                     title = link = description = "";
                 } else if (tag.equals("title")) {
                     xpp.next(); // Skip to next element -- assume text is directly inside the tag
                     title = xpp.getText();
                 } else if (tag.equals("link")) {
                     xpp.next();
                     link = xpp.getText();
                 } else if (tag.equals("description")) {
                     xpp.next();
                     description = xpp.getText();
                 }
             } else if (eventType == XmlPullParser.END_TAG) {
                 // We have a comlete item -- post it back to the UI
                 // using the mHandler (necessary because we are not
                 // running on the UI thread).
                 String tag = xpp.getName();
                 if (tag.equals("item")) {
                     RssItem item = new RssItem(title, link, description);
                     mHandler.post(new ItemAdder(item));
                 }
             }
             eventType = xpp.next();
         }
     }

     // SAX version of the code to do the parsing.
     /*
     private class RSSHandler extends DefaultHandler {
         RSSListAdapter mAdapter;

         String mTitle;
         String mLink;
         String mDescription;

         StringBuilder mBuff;

         boolean mInItem;

         public RSSHandler(RSSListAdapter adapter) {
             mAdapter = adapter;
             mInItem = false;
             mBuff = new StringBuilder();
         }

         public void startElement(String uri,
                 String localName,
                 String qName,
                 Attributes atts)
                 throws SAXException {
             String tag = localName;
             if (tag.equals("")) tag = qName;

             // If inside <item>, clear out buff on each tag start
             if (mInItem) {
                 mBuff.delete(0, mBuff.length());
             }

             if (tag.equals("item")) {
                 mTitle = mLink = mDescription = "";
                 mInItem = true;
             }
         }

         public void characters(char[] ch,
                       int start,
                       int length)
                       throws SAXException {
             // Buffer up all the chars when inside <item>
             if (mInItem) mBuff.append(ch, start, length);
         }

         public void endElement(String uri,
                       String localName,
                       String qName)
                       throws SAXException {
             String tag = localName;
             if (tag.equals("")) tag = qName;

             // For each tag, copy buff chars to right variable
             if (tag.equals("title")) mTitle = mBuff.toString();
             else if (tag.equals("link")) mLink = mBuff.toString();
             if (tag.equals("description")) mDescription = mBuff.toString();

             // Have all the data at this point .... post it to the UI.
             if (tag.equals("item")) {
                 RssItem item = new RssItem(mTitle, mLink, mDescription);
                 mHandler.post(new ItemAdder(item));
                 mInItem = false;
             }
         }
     }
     */

     /*
     public void parseRSS2(InputStream in, RSSListAdapter adapter) throws IOException {
             SAXParser parser = SAXParserFactory.newInstance().newSAXParser();
             DefaultHandler handler = new RSSHandler(adapter);

             parser.parse(in, handler);
             // TODO: does the parser figure out the encoding right on its own?
     }
     */
 }
	/*
	* Copyright (C) 2007 The Android Open Source Project
	*
	* Licensed under the Apache License, Version 2.0 (the "License");
	* you may not use this file except in compliance with the License.
	* You may obtain a copy of the License at
	*
	* http://www.apache.org/licenses/LICENSE-2.0
	*
	* Unless required by applicable law or agreed to in writing, software
	* distributed under the License is distributed on an "AS IS" BASIS,
	* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	* See the License for the specific language governing permissions and
	* limitations under the License.
	*/

	package com.example.android.rssreader;

	import org.xmlpull.v1.XmlPullParser;
	import org.xmlpull.v1.XmlPullParserException;

	import android.app.ListActivity;
	import android.content.Context;
	import android.content.Intent;
	import android.net.Uri;
	import android.os.Bundle;
	import android.os.Handler;
	import android.view.Menu;
	import android.view.MenuItem;
	import android.view.View;
	import android.view.View.OnClickListener;
	import android.view.ViewGroup;
	import android.view.LayoutInflater;
	import android.widget.ArrayAdapter;
	import android.widget.Button;
	import android.widget.EditText;
	import android.widget.ListView;
	import android.widget.TextView;
	import android.widget.TwoLineListItem;
	import android.util.Xml;

	import java.io.IOException;
	import java.io.InputStream;
	import java.net.URL;
	import java.net.URLConnection;
	import java.util.ArrayList;
	import java.util.List;

	/**
	* The RssReader example demonstrates forking off a thread to download
	* rss data in the background and post the results to a ListView in the UI.
	* It also shows how to display custom data in a ListView
	* with a ArrayAdapter subclass.
	*
	* <ul>
	* <li>We own a ListView
	* <li>The ListView uses our custom RSSListAdapter which
	* <ul>
	* <li>The adapter feeds data to the ListView
	* <li>Override of getView() in the adapter provides the display view
	* used for selected list items
	* </ul>
	* <li>Override of onListItemClick() creates an intent to open the url for that
	* RssItem in the browser.
	* <li>Download = fork off a worker thread
	* <li>The worker thread opens a network connection for the rss data
	* <li>Uses XmlPullParser to extract the rss item data
	* <li>Uses mHandler.post() to send new RssItems to the UI
	* <li>Supports onSaveInstanceState()/onRestoreInstanceState() to save list/selection state on app
	* pause, so can resume seamlessly
	* </ul>
	*/
	public class RssReader extends ListActivity {
	/**
	* Custom list adapter that fits our rss data into the list.
	*/
	private RSSListAdapter mAdapter;

	/**
	* Url edit text field.
	*/
	private EditText mUrlText;

	/**
	* Status text field.
	*/
	private TextView mStatusText;

	/**
	* Handler used to post runnables to the UI thread.
	*/
	private Handler mHandler;

	/**
	* Currently running background network thread.
	*/
	private RSSWorker mWorker;

	// Take this many chars from the front of the description.
	public static final int SNIPPET_LENGTH = 90;


	// Keys used for data in the onSaveInstanceState() Map.
	public static final String STRINGS_KEY = "strings";

	public static final String SELECTION_KEY = "selection";

	public static final String URL_KEY = "url";

	public static final String STATUS_KEY = "status";

	/**
	* Called when the activity starts up. Do activity initialization
	* here, not in a constructor.
	*
	* @see Activity#onCreate
	*/
	@Override
	protected void onCreate(Bundle savedInstanceState) {
	super.onCreate(savedInstanceState);

	setContentView(R.layout.rss_layout);
	// The above layout contains a list id "android:list"
	// which ListActivity adopts as its list -- we can
	// access it with getListView().

	// Install our custom RSSListAdapter.
	List<RssItem> items = new ArrayList<RssItem>();
	mAdapter = new RSSListAdapter(this, items);
	getListView().setAdapter(mAdapter);

	// Get pointers to the UI elements in the rss_layout
	mUrlText = (EditText)findViewById(R.id.urltext);
	mStatusText = (TextView)findViewById(R.id.statustext);

	Button download = (Button)findViewById(R.id.download);
	download.setOnClickListener(new OnClickListener() {
	public void onClick(View v) {
	doRSS(mUrlText.getText());
	}
	});

	// Need one of these to post things back to the UI thread.
	mHandler = new Handler();

	// NOTE: this could use the icicle as done in
	// onRestoreInstanceState().
	}

	/**
	* ArrayAdapter encapsulates a java.util.List of T, for presentation in a
	* ListView. This subclass specializes it to hold RssItems and display
	* their title/description data in a TwoLineListItem.
	*/
	private class RSSListAdapter extends ArrayAdapter<RssItem> {
	private LayoutInflater mInflater;

	public RSSListAdapter(Context context, List<RssItem> objects) {
	super(context, 0, objects);

	mInflater = (LayoutInflater)context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
	}

	/**
	* This is called to render a particular item for the on screen list.
	* Uses an off-the-shelf TwoLineListItem view, which contains text1 and
	* text2 TextViews. We pull data from the RssItem and set it into the
	* view. The convertView is the view from a previous getView(), so
	* we can re-use it.
	*
	* @see ArrayAdapter#getView
	*/
	@Override
	public View getView(int position, View convertView, ViewGroup parent) {
	TwoLineListItem view;

	// Here view may be passed in for re-use, or we make a new one.
	if (convertView == null) {
	view = (TwoLineListItem) mInflater.inflate(android.R.layout.simple_list_item_2,
	null);
	} else {
	view = (TwoLineListItem) convertView;
	}

	RssItem item = this.getItem(position);

	// Set the item title and description into the view.
	// This example does not render real HTML, so as a hack to make
	// the description look better, we strip out the
	// tags and take just the first SNIPPET_LENGTH chars.
	view.getText1().setText(item.getTitle());
	String descr = item.getDescription().toString();
	descr = removeTags(descr);
	view.getText2().setText(descr.substring(0, Math.min(descr.length(), SNIPPET_LENGTH)));
	return view;
	}

	}

	/**
	* Simple code to strip out <tag>s -- primitive way to sortof display HTML as
	* plain text.
	*/
	public String removeTags(String str) {
	str = str.replaceAll("<.*?>", " ");
	str = str.replaceAll("\\s+", " ");
	return str;
	}

	/**
	* Called when user clicks an item in the list. Starts an activity to
	* open the url for that item.
	*/
	@Override
	protected void onListItemClick(ListView l, View v, int position, long id) {
	RssItem item = mAdapter.getItem(position);

	// Creates and starts an intent to open the item.link url.
	Intent intent = new Intent(Intent.ACTION_VIEW, Uri.parse(item.getLink().toString()));
	startActivity(intent);
	}

	/**
	* Resets the output UI -- list and status text empty.
	*/
	public void resetUI() {
	// Reset the list to be empty.
	List<RssItem> items = new ArrayList<RssItem>();
	mAdapter = new RSSListAdapter(this, items);
	getListView().setAdapter(mAdapter);

	mStatusText.setText("");
	mUrlText.requestFocus();
	}

	/**
	* Sets the currently active running worker. Interrupts any earlier worker,
	* so we only have one at a time.
	*
	* @param worker the new worker
	*/
	public synchronized void setCurrentWorker(RSSWorker worker) {
	if (mWorker != null) mWorker.interrupt();
	mWorker = worker;
	}

	/**
	* Is the given worker the currently active one.
	*
	* @param worker
	* @return
	*/
	public synchronized boolean isCurrentWorker(RSSWorker worker) {
	return (mWorker == worker);
	}

	/**
	* Given an rss url string, starts the rss-download-thread going.
	*
	* @param rssUrl
	*/
	private void doRSS(CharSequence rssUrl) {
	RSSWorker worker = new RSSWorker(rssUrl);
	setCurrentWorker(worker);

	resetUI();
	mStatusText.setText("Downloading\u2026");

	worker.start();
	}

	/**
	* Runnable that the worker thread uses to post RssItems to the
	* UI via mHandler.post
	*/
	private class ItemAdder implements Runnable {
	RssItem mItem;

	ItemAdder(RssItem item) {
	mItem = item;
	}

	public void run() {
	mAdapter.add(mItem);
	}

	// NOTE: Performance idea -- would be more efficient to have he option
	// to add multiple items at once, so you get less "update storm" in the UI
	// compared to adding things one at a time.
	}

	/**
	* Worker thread takes in an rss url string, downloads its data, parses
	* out the rss items, and communicates them back to the UI as they are read.
	*/
	private class RSSWorker extends Thread {
	private CharSequence mUrl;

	public RSSWorker(CharSequence url) {
	mUrl = url;
	}

	@Override
	public void run() {
	String status = "";
	try {
	// Standard code to make an HTTP connection.
	URL url = new URL(mUrl.toString());
	URLConnection connection = url.openConnection();
	connection.setConnectTimeout(10000);

	connection.connect();
	InputStream in = connection.getInputStream();

	parseRSS(in, mAdapter);
	status = "done";
	} catch (Exception e) {
	status = "failed:" + e.getMessage();
	}

	// Send status to UI (unless a newer worker has started)
	// To communicate back to the UI from a worker thread,
	// pass a Runnable to handler.post().
	final String temp = status;
	if (isCurrentWorker(this)) {
	mHandler.post(new Runnable() {
	public void run() {
	mStatusText.setText(temp);
	}
	});
	}
	}
	}

	/**
	* Populates the menu.
	*/
	@Override
	public boolean onCreateOptionsMenu(Menu menu) {
	super.onCreateOptionsMenu(menu);

	menu.add(0, 0, 0, "Slashdot")
	.setOnMenuItemClickListener(new RSSMenu("http://rss.slashdot.org/Slashdot/slashdot"));

	menu.add(0, 0, 0, "Google News")
	.setOnMenuItemClickListener(new RSSMenu("http://news.google.com/?output=rss"));

	menu.add(0, 0, 0, "News.com")
	.setOnMenuItemClickListener(new RSSMenu("http://news.com.com/2547-1_3-0-20.xml"));

	menu.add(0, 0, 0, "Bad Url")
	.setOnMenuItemClickListener(new RSSMenu("http://nifty.stanford.edu:8080"));

	menu.add(0, 0, 0, "Reset")
	.setOnMenuItemClickListener(new MenuItem.OnMenuItemClickListener() {
	public boolean onMenuItemClick(MenuItem item) {
	resetUI();
	return true;
	}
	});

	return true;
	}

	/**
	* Puts text in the url text field and gives it focus. Used to make a Runnable
	* for each menu item. This way, one inner class works for all items vs. an
	* anonymous inner class for each menu item.
	*/
	private class RSSMenu implements MenuItem.OnMenuItemClickListener {
	private CharSequence mUrl;

	RSSMenu(CharSequence url) {
	mUrl = url;
	}

	public boolean onMenuItemClick(MenuItem item) {
	mUrlText.setText(mUrl);
	mUrlText.requestFocus();
	return true;
	}
	}


	/**
	* Called for us to save out our current state before we are paused,
	* such a for example if the user switches to another app and memory
	* gets scarce. The given outState is a Bundle to which we can save
	* objects, such as Strings, Integers or lists of Strings. In this case, we
	* save out the list of currently downloaded rss data, (so we don't have to
	* re-do all the networking just because the user goes back and forth
	* between aps) which item is currently selected, and the data for the text views.
	* In onRestoreInstanceState() we look at the map to reconstruct the run-state of the
	* application, so returning to the activity looks seamlessly correct.
	* TODO: the Activity javadoc should give more detail about what sort of
	* data can go in the outState map.
	*
	* @see android.app.Activity#onSaveInstanceState
	*/
	@SuppressWarnings("unchecked")
	@Override
	protected void onSaveInstanceState(Bundle outState) {
	super.onSaveInstanceState(outState);

	// Make a List of all the RssItem data for saving
	// NOTE: there may be a way to save the RSSItems directly,
	// rather than their string data.
	int count = mAdapter.getCount();

	// Save out the items as a flat list of CharSequence objects --
	// title0, link0, descr0, title1, link1, ...
	ArrayList<CharSequence> strings = new ArrayList<CharSequence>();
	for (int i = 0; i < count; i++) {
	RssItem item = mAdapter.getItem(i);
	strings.add(item.getTitle());
	strings.add(item.getLink());
	strings.add(item.getDescription());
	}
	outState.putSerializable(STRINGS_KEY, strings);

	// Save current selection index (if focussed)
	if (getListView().hasFocus()) {
	outState.putInt(SELECTION_KEY, Integer.valueOf(getListView().getSelectedItemPosition()));
	}

	// Save url
	outState.putString(URL_KEY, mUrlText.getText().toString());

	// Save status
	outState.putCharSequence(STATUS_KEY, mStatusText.getText());
	}

	/**
	* Called to "thaw" re-animate the app from a previous onSaveInstanceState().
	*
	* @see android.app.Activity#onRestoreInstanceState
	*/
	@SuppressWarnings("unchecked")
	@Override
	protected void onRestoreInstanceState(Bundle state) {
	super.onRestoreInstanceState(state);

	// Note: null is a legal value for onRestoreInstanceState.
	if (state == null) return;

	// Restore items from the big list of CharSequence objects
	List<CharSequence> strings = (ArrayList<CharSequence>)state.getSerializable(STRINGS_KEY);
	List<RssItem> items = new ArrayList<RssItem>();
	for (int i = 0; i < strings.size(); i += 3) {
	items.add(new RssItem(strings.get(i), strings.get(i + 1), strings.get(i + 2)));
	}

	// Reset the list view to show this data.
	mAdapter = new RSSListAdapter(this, items);
	getListView().setAdapter(mAdapter);

	// Restore selection
	if (state.containsKey(SELECTION_KEY)) {
	getListView().requestFocus(View.FOCUS_FORWARD);
	// todo: is above right? needed it to work
	getListView().setSelection(state.getInt(SELECTION_KEY));
	}

	// Restore url
	mUrlText.setText(state.getCharSequence(URL_KEY));

	// Restore status
	mStatusText.setText(state.getCharSequence(STATUS_KEY));
	}



	/**
	* Does rudimentary RSS parsing on the given stream and posts rss items to
	* the UI as they are found. Uses Android's XmlPullParser facility. This is
	* not a production quality RSS parser -- it just does a basic job of it.
	*
	* @param in stream to read
	* @param adapter adapter for ui events
	*/
	void parseRSS(InputStream in, RSSListAdapter adapter) throws IOException,
	XmlPullParserException {
	// TODO: switch to sax

	XmlPullParser xpp = Xml.newPullParser();
	xpp.setInput(in, null); // null = default to UTF-8

	int eventType;
	String title = "";
	String link = "";
	String description = "";
	eventType = xpp.getEventType();
	while (eventType != XmlPullParser.END_DOCUMENT) {
	if (eventType == XmlPullParser.START_TAG) {
	String tag = xpp.getName();
	if (tag.equals("item")) {
	title = link = description = "";
	} else if (tag.equals("title")) {
	xpp.next(); // Skip to next element -- assume text is directly inside the tag
	title = xpp.getText();
	} else if (tag.equals("link")) {
	xpp.next();
	link = xpp.getText();
	} else if (tag.equals("description")) {
	xpp.next();
	description = xpp.getText();
	}
	} else if (eventType == XmlPullParser.END_TAG) {
	// We have a comlete item -- post it back to the UI
	// using the mHandler (necessary because we are not
	// running on the UI thread).
	String tag = xpp.getName();
	if (tag.equals("item")) {
	RssItem item = new RssItem(title, link, description);
	mHandler.post(new ItemAdder(item));
	}
	}
	eventType = xpp.next();
	}
	}

	// SAX version of the code to do the parsing.
	/*
	private class RSSHandler extends DefaultHandler {
	RSSListAdapter mAdapter;

	String mTitle;
	String mLink;
	String mDescription;

	StringBuilder mBuff;

	boolean mInItem;

	public RSSHandler(RSSListAdapter adapter) {
	mAdapter = adapter;
	mInItem = false;
	mBuff = new StringBuilder();
	}

	public void startElement(String uri,
	String localName,
	String qName,
	Attributes atts)
	throws SAXException {
	String tag = localName;
	if (tag.equals("")) tag = qName;

	// If inside <item>, clear out buff on each tag start
	if (mInItem) {
	mBuff.delete(0, mBuff.length());
	}

	if (tag.equals("item")) {
	mTitle = mLink = mDescription = "";
	mInItem = true;
	}
	}

	public void characters(char[] ch,
	int start,
	int length)
	throws SAXException {
	// Buffer up all the chars when inside <item>
	if (mInItem) mBuff.append(ch, start, length);
	}

	public void endElement(String uri,
	String localName,
	String qName)
	throws SAXException {
	String tag = localName;
	if (tag.equals("")) tag = qName;

	// For each tag, copy buff chars to right variable
	if (tag.equals("title")) mTitle = mBuff.toString();
	else if (tag.equals("link")) mLink = mBuff.toString();
	if (tag.equals("description")) mDescription = mBuff.toString();

	// Have all the data at this point .... post it to the UI.
	if (tag.equals("item")) {
	RssItem item = new RssItem(mTitle, mLink, mDescription);
	mHandler.post(new ItemAdder(item));
	mInItem = false;
	}
	}
	}
	*/

	/*
	public void parseRSS2(InputStream in, RSSListAdapter adapter) throws IOException {
	SAXParser parser = SAXParserFactory.newInstance().newSAXParser();
	DefaultHandler handler = new RSSHandler(adapter);

	parser.parse(in, handler);
	// TODO: does the parser figure out the encoding right on its own?
	}
	*/
	}