Read RSS in background, using AsyncTask

Here is a further work of the previous exercise "Simple RSS Reader, with Options Menu to reload RSS", with the help of "AsyncTask: perform background operations and publish results on the UI thread". The original readRss() method is broke into three section, preReadRss(), readRss() and displayRss(). and are called inside AsyncTask's onPreExecute() , doInBackground() and onPostExecute(). Such that the time-consume task can be moved to run in background.



AndroidRssReader.java

package com.exercise.AndroidRssReader;

import java.io.IOException;
import java.net.MalformedURLException;
import java.net.URL;
import java.util.Calendar;
import java.util.List;

import javax.xml.parsers.ParserConfigurationException;
import javax.xml.parsers.SAXParser;
import javax.xml.parsers.SAXParserFactory;

import org.xml.sax.InputSource;
import org.xml.sax.SAXException;
import org.xml.sax.XMLReader;

import android.app.ListActivity;
import android.content.Context;
import android.content.Intent;
import android.os.AsyncTask;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import android.widget.TextView;
import android.widget.Toast;

public class AndroidRssReader extends ListActivity {

public class RssLoadingTask extends AsyncTask<Void, Void, Void> {

 @Override
 protected void onPostExecute(Void result) {
  // TODO Auto-generated method stub
  displayRss();
 }

 @Override
 protected void onPreExecute() {
  // TODO Auto-generated method stub
  preReadRss();
 }

 @Override
 protected void onProgressUpdate(Void... values) {
  // TODO Auto-generated method stub
  //super.onProgressUpdate(values);
 }

 @Override
 protected Void doInBackground(Void... arg0) {
  // TODO Auto-generated method stub
  readRss();
  return null;
 }

}

private RSSFeed myRssFeed = null;

TextView feedTitle;
TextView feedDescribtion;
TextView feedPubdate;
TextView feedLink;

public class MyCustomAdapter extends ArrayAdapter<RSSItem> {

 public MyCustomAdapter(Context context, int textViewResourceId,
   List<RSSItem> list) {
  super(context, textViewResourceId, list);
 }

 @Override
 public View getView(int position, View convertView, ViewGroup parent) {
  // TODO Auto-generated method stub
  //return super.getView(position, convertView, parent);
 
  View row = convertView;
  
  if(row==null){
   LayoutInflater inflater=getLayoutInflater();
   row=inflater.inflate(R.layout.row, parent, false);
  }
 
  TextView listTitle=(TextView)row.findViewById(R.id.listtitle);
  listTitle.setText(myRssFeed.getList().get(position).getTitle());
  TextView listPubdate=(TextView)row.findViewById(R.id.listpubdate);
  listPubdate.setText(myRssFeed.getList().get(position).getPubdate());

  if (position%2 == 0){
   listTitle.setBackgroundColor(0xff101010);
   listPubdate.setBackgroundColor(0xff101010);
  }
  else{
   listTitle.setBackgroundColor(0xff080808);
   listPubdate.setBackgroundColor(0xff080808);
  }
 
  return row;
 }
}

   /** Called when the activity is first created. */
   @Override
   public void onCreate(Bundle savedInstanceState) {
       super.onCreate(savedInstanceState);
       setContentView(R.layout.main);
      
 feedTitle = (TextView)findViewById(R.id.feedtitle);
 feedDescribtion = (TextView)findViewById(R.id.feeddescribtion);
 feedPubdate = (TextView)findViewById(R.id.feedpubdate);
 feedLink = (TextView)findViewById(R.id.feedlink);
      
       startReadRss();
   }
  
   private void startReadRss(){
    new RssLoadingTask().execute();
   }
  
   private void preReadRss()
   {
    feedTitle.setText("--- wait ---");
 feedDescribtion.setText("");
 feedPubdate.setText("");
 feedLink.setText("");
 setListAdapter(null);

 Toast.makeText(this, "Reading RSS, Please wait.", Toast.LENGTH_LONG).show();
   }
  
   private void readRss(){
   

   
       try {
  URL rssUrl = new URL("http://www.gov.hk/en/about/rss/govhkrss.data.xml");
  SAXParserFactory mySAXParserFactory = SAXParserFactory.newInstance();
  SAXParser mySAXParser = mySAXParserFactory.newSAXParser();
  XMLReader myXMLReader = mySAXParser.getXMLReader();
  RSSHandler myRSSHandler = new RSSHandler();
  myXMLReader.setContentHandler(myRSSHandler);
  InputSource myInputSource = new InputSource(rssUrl.openStream());
  myXMLReader.parse(myInputSource);
 
  myRssFeed = myRSSHandler.getFeed();
 
 } catch (MalformedURLException e) {
  // TODO Auto-generated catch block
  e.printStackTrace();
 } catch (ParserConfigurationException e) {
  // TODO Auto-generated catch block
  e.printStackTrace();
 } catch (SAXException e) {
  // TODO Auto-generated catch block
  e.printStackTrace();
 } catch (IOException e) {
  // TODO Auto-generated catch block
  e.printStackTrace();
 }
   }

   private void displayRss()
   {
 if (myRssFeed!=null)
 {
  Calendar c = Calendar.getInstance();
     String strCurrentTiime =  "\n(Time of Reading - "
           + c.get(Calendar.HOUR_OF_DAY)
           + " : "
           + c.get(Calendar.MINUTE) + ")\n";

  feedTitle.setText(myRssFeed.getTitle() + strCurrentTiime);
  feedDescribtion.setText(myRssFeed.getDescription());
  feedPubdate.setText(myRssFeed.getPubdate());
  feedLink.setText(myRssFeed.getLink());
 
  MyCustomAdapter adapter =
   new MyCustomAdapter(this, R.layout.row, myRssFeed.getList());
  setListAdapter(adapter);
 
 }
   }

@Override
protected void onListItemClick(ListView l, View v, int position, long id) {
 // TODO Auto-generated method stub
 Intent intent = new Intent(this,ShowDetails.class);
 Bundle bundle = new Bundle();
 bundle.putString("keyTitle", myRssFeed.getItem(position).getTitle());
 bundle.putString("keyDescription", myRssFeed.getItem(position).getDescription());
 bundle.putString("keyLink", myRssFeed.getItem(position).getLink());
 bundle.putString("keyPubdate", myRssFeed.getItem(position).getPubdate());
 intent.putExtras(bundle);
       startActivity(intent);
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
 // TODO Auto-generated method stub
 menu.add(0, 0, 0, "Reload");
 return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
 // TODO Auto-generated method stub
 switch(item.getItemId()){
 case (0): startReadRss();
   break;
 default:
   break;
 }

 return true;
}  
}

Download the files.