1、新线程
new Thread(runnable).start();
2、执行下载操作
Runnable runnable = new Runnable() {
        @Override
        public void run() {
                            //执行下载操作
                    Message msg = new Message();
//发送结果
            handler.sendMessage(msg);
        }
    };

    private Handler handler = new Handler() {
        @Override
        // 当有消息发送出来的时候就执行Handler的这个方法
        public void handleMessage(Message msg) {
            try {
                //处理结果
                           } catch (Exception e) {
                Log.e(e.getMessage(), e.toString());
            }

        }
    };        

package com.example.tools;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;

public class HttpDownLoad {
    public String Download(String url) {
        StringBuilder sb = new StringBuilder();
        BufferedReader br = null;
        String s;
        try {
            URL r = new URL(url);
            HttpURLConnection con = (HttpURLConnection) r.openConnection();
            br = new BufferedReader(new InputStreamReader(con.getInputStream()));
            while ((s = br.readLine()) != null) {
                sb.append(s);
            }
        } catch (Exception ex) {
            ex.printStackTrace();

        } finally {
            try {
                br.close();
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
        return sb.toString();
    }

    public InputStream GetInputStream(String url) {
        try {
            URL r = new URL(url);
            HttpURLConnection con = (HttpURLConnection) r.openConnection();
            InputStream input = con.getInputStream();
            return input;
        } catch (Exception ex) {
            ex.printStackTrace();
            return null;
        }
    }
}

package cn.itcast.service;

import java.io.InputStream;
import java.util.ArrayList;
import java.util.List;

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

import org.xml.sax.Attributes;
import org.xml.sax.SAXException;
import org.xml.sax.helpers.DefaultHandler;

import cn.itcast.model.Person;

public class SAXPersonService {
   public List<Person> getPersons(InputStream inStream) throws Throwable
   {
       SAXParserFactory factory = SAXParserFactory.newInstance();//工厂模式还是单例模式？
       SAXParser parser =factory.newSAXParser();
       PersonParse personParser =new PersonParse();
       parser.parse(inStream, personParser);
       inStream.close();
       return personParser.getPerson();
   }
   private final class PersonParse extends DefaultHandler
   {

    private List<Person> list = null;
    Person person =null;
    private String tag=null;

    public List<Person> getPerson() {
        return list;
    }
    @Override
    public void startDocument() throws SAXException {
        list =new ArrayList<Person>();
    }

    @Override
    public void startElement(String uri, String localName, String qName,
            Attributes attributes) throws SAXException {
        if("person".equals(localName))
        {
            //xml元素节点开始时触发，是“person”
            person = new Person();
            person.setId(new Integer(attributes.getValue(0)));
        }
        tag =localName;//保存元素节点名称
    }
    @Override
    public void endElement(String uri, String localName, String qName)
            throws SAXException {
        //元素节点结束时触发，是“person”
        if("person".equals(localName))
        {
            list.add(person);
            person=null;
        }
        tag =null;//结束时，需要清空tag
        }
    @Override
    public void characters(char[] ch, int start, int length)
            throws SAXException {
        if(tag!=null)
        {
            String data = new String(ch,start,length);
           if("name".equals(tag))
           {
               person.setName(data);

           }else if("age".equals(tag))
           {
               person.setAge(new Integer(data));
           }
        }
    }

   }
}