android4.4中關於不能再主線程下載和在主線程中更新UI的矛盾

本人每次在使用android時總是喜歡用最新的sdk（其實是做系統就刪了），這樣就發現不知從什麼時候起android就不讓在主線程中下載東西，即使是很小的東西東不行。這也算是對程序的規范吧，因為如果在一段時間中不能下載完成，主線程一直處於假死狀態，系統會強制關閉的。然而，我們經常需要在下載數據以後進行UI的更新。這又造成兩個不在一個線程中。下面貼出一些代碼來解決這個問題。

package com.yx.mp3player;

import java.io.StringReader;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;

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

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

import com.yx.download.HttpDownload;
import com.yx.model.Mp3Info;
import com.yx.xml.Mp3ListContentHandler;

import android.os.Bundle;
import android.os.Handler;
import android.os.HandlerThread;
import android.app.Activity;
import android.app.ListActivity;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.SimpleAdapter;

public class Mp3ListActivity extends ListActivity {

private static final int UPDATE = 1;
private static final int ABOUT = 1;
private HandlerThread handlerThread;
private Handler handler;
private List mp3Infos = null;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_mp3_list);
handler = new Handler();
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.mp3_list, menu);
menu.add(0, UPDATE, 1, "更新");
menu.add(0, ABOUT, 2, "關於");
return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
if(1==item.getItemId()){
//用戶點擊更新按鈕
new Thread(new Runnable() {
@Override
public void run() {
//實現下載
String xmlStr;
xmlStr = downLoadXML("http://192.168.0.103:8080/mp3/resouces.xml");
mp3Infos = parse(xmlStr);
handler.post(new Runnable(){
@Override
public void run() {

//更新UI

List> list = new ArrayList>();
for (Iterator iterator = mp3Infos.iterator(); iterator.hasNext();) {
Mp3Info mp3Info = (Mp3Info) iterator.next();
HashMap map = new HashMap();
map.put("mp3_name", mp3Info.getMp3Name());
map.put("mp3_size", mp3Info.getMp3Size());
list.add(map);
}
SimpleAdapter simpleAdapter = new SimpleAdapter(Mp3ListActivity.this, list,
R.layout.mp3info_item,
new String[]{"mp3_name","mp3_size"},
new int[]{R.id.mp3_name,R.id.mp3_size});
setListAdapter(simpleAdapter);
System.out.println("=================");
}});
}
}).start();


}else if(ABOUT==item.getItemId()){
//用戶點擊了關於按鈕
}
return super.onOptionsItemSelected(item);
}



public String downLoadXML(String urlstr){
HttpDownload httpDownloader = new HttpDownload();
String result = httpDownloader.downLoad(urlstr);
System.out.println("XML--->"+result);
return result;
}

private List parse(String xmlStr){
List infos = new ArrayList();
SAXParserFactory saxParserFactory = SAXParserFactory.newInstance();
try {
XMLReader xmlReader= saxParserFactory.newSAXParser().getXMLReader();
Mp3ListContentHandler mp3ListContentHandler = new Mp3ListContentHandler(infos);
xmlReader.setContentHandler(mp3ListContentHandler);
xmlReader.parse(new InputSource(new StringReader(xmlStr)));
} catch (Exception e) {
e.printStackTrace();
}
return infos;
}
}