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从网络读取数据并动态的显示在ListView中

11-11-29 来源：[db:作者]

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这两天写了个小程序，使用了从网络读取xml数据，并显示在ListView中。

这里面有几个关键点：

从网络读取数据

SAX解析xml

异步填充ListView

先看下截图:

非常简单的界面哈

为了方便，我再自己的服务器上，放了一个xml文件，其内容主要是：

<?xml version="1.0"?>

<name>android dev</name>

</product>

<name>androiddev2</name>

</product>

</products>

该程序，首先用一个AsyncTask新启一个线程，来下载和解析xml；和主线程通过Handler对象来通讯。

下载XML文件

通过HTTPGet来下载xml。这时apache提供的包，需要首先包含如下包：

import org.apache.http.HttpEntity;

import org.apache.http.HttpResponse;

import org.apache.http.HttpStatus;

import org.apache.http.client.HttpClient;

import org.apache.http.client.methods.HttpGet;

import org.apache.http.impl.client.DefaultHttpClient;

代码如下：(使用Get方法)

protected String doInBackground(String... params) {

HttpGet httpRequest = new HttpGet(params[0]); //从url 创建一个HttpGet对象

HttpClient httpclient = new DefaultHttpClient();

//mShowHtml.setText("");

try {

HttpResponse httpResponse = httpclient.execute(httpRequest);

if(httpResponse.getStatusLine().getStatusCode() == HttpStatus.SC_OK){//获取http的返回值代码

HttpEntity entitiy = httpResponse.getEntity();

InputStream in = entitiy.getContent();//获得内容

//解析xml，下面详述

InputSource source = new InputSource(in);

SAXParserFactory sax = SAXParserFactory.newInstance();

XMLReader xmlReader = sax.newSAXParser().getXMLReader();

xmlReader.setContentHandler(new ProductHandler());

xmlReader.parse(source);

}

else {

//return "请求失败!";

//mShowHtml.setText("请求失败");

//Message mymsg = mMainHandler.obtainMessage();

//mymsg.obj = "请求失败";

//mMainHandler.sendMessage(mymsg);

}

}catch(IOException e){

e.printStackTrace();

}catch(SAXException e) {

e.printStackTrace();

}catch(ParserConfigurationException e) {

e.printStackTrace();

}

return null;

}

解析XML

使用SAX的解析方法，先包含必须得包

import org.xml.sax.InputSource;

import org.xml.sax.SAXException;

import org.xml.sax.XMLReader;

import org.xml.sax.helpers.DefaultHandler;

解析的代码，正如上面所示：

//InputSource是解析源，可以通过一个InputStream创建

urce source = new InputSource(in);

SAXParserFactory sax = SAXParserFactory.newInstance();

der xmlReader = sax.newSAXParser().getXMLReader();

xmlReader.setContentHandler(new ProductHandler());//ProductHandler是解析的句柄

der.parse(source);

SAX主要使用ContentHandler接口来传递解析好得数据，不过，更经常使用的是DefaultHandler

class ProductHandler extends DefaultHandler { //从DefaultHandler继承即可

private ProductInfo curProduct;

private String content;

//解析到一个标签时调用

public void startElement(String uri, String localName, String name, org.xml.sax.Attributes attributes) throws SAXException {

if(localName.equals("product")) {//遇到product标签，进行解析

curProduct = new ProductInfo();

}

else if(localName.equals("image")) {

//set name

curProduct.image = attributes.getValue("src");//提取image src属性

}

super.startElement(uri, localName, name, attributes);

}

public void endElement(String uri, String localName, String name) throws SAXException{

if(localName.equals("product")) {//当解析到一个标签结束时，发送一个消息，把Product类作为参数传递

//send event

//get main handler

Message msg = mMainHandler.obtainMessage();

msg.obj = curProduct;

mMainHandler.sendMessage(msg);

//Log.i("Product:", curProduct.toString());

}

else if(localName.equals("name")) {

//set name

curProduct.name = content;//保存名字

}

else if(localName.equals("price")) {

curProduct.price = Float.parseFloat(content);<span style="background-color: rgb(255, 255, 255); ">//保存价格</span>

}

super.endElement(uri, localName, name);

}

//这里获取具体的内容，是标签下保存的文本

public void characters (char[] ch, int start, int length) throws SAXException

{

content = new String(ch, start, length);

//Log.i("Parser:" ,content);

super.characters(ch, start, length);

}

ProductInfo类的定义非常简单

class ProductInfo {

public String name;

public float price;

public String image;

public String toString() {

return "\nName:" + name +"\nPrice :" + price + "\nImage:" + image;

}

在AsyncTask中执行以上代码

public class GetHttpTask extends AsyncTask<String, Integer, String> {

public GetHttpTask() {

}

protected void onPreExecute() { //在进入线程之前执行。该函数在调用者线程内执行

}

protected String doInBackground(String... params) {//线程的执行主体

HttpGet httpRequest = new HttpGet(params[0]);

.................. //主要执行下载和解析的嗲吗

return null;

}

protected void onPostExecute(String result) {//完成后调用

}

在主线程中，调用GetHttpTask的execute方法就可以执行

btn.setOnClickListener(new View.OnClickListener() {//在onCreate函数中调用

@Override

public void onClick(View v) {

// TODO Auto-generated method stub

httpGet();

}

});

httpGet方法：

void httpGet() {

GetHttpTask task = new GetHttpTask();

task.execute("http://192.168.1.111:8080/nfcdemo/products.xml");

}

异步传递消息

上面的例子中，在endElement函数中，发送了消息，下面是接收消息

在主Activity中，声明了一个Handler mHandler对象，并在onCreate时，这样做

mMainHandler = new Handler() {

public void handleMessage(Message msg) {

//mShowHtml.append((String)msg.obj);

if(msg.obj != null) {

ProductInfo prod = (ProductInfo)msg.obj;

Log.i("Prodcut:", prod.toString());

//mShowHtml.append(prod.toString());

HashMap<String, Object> map = new HashMap<String, Object>();

map.put("name", prod.name);

map.put("price", "RMB" + prod.price);

mlist.add(map); //mlist保存了列表的具体数据

mProdList.notifyDataSetChanged();//mProdList是一个ListView对象，该函数引起ListView重读数据

}

};

这个过程的要点基本如上，贴上所有代码吧！关于ListView的用法，可以参考http://blog.csdn.net/hellogv/article/details/4542668

主代码：

package com.test.http;

import java.io.IOException;

import java.io.InputStream;

import java.util.ArrayList;

import java.util.HashMap;

import javax.xml.parsers.ParserConfigurationException;

import javax.xml.parsers.SAXParserFactory;

import org.apache.http.HttpEntity;

import org.apache.http.HttpResponse;

import org.apache.http.HttpStatus;

import org.apache.http.client.HttpClient;

import org.apache.http.client.methods.HttpGet;

import org.apache.http.impl.client.DefaultHttpClient;

import org.xml.sax.InputSource;

import org.xml.sax.SAXException;

import org.xml.sax.XMLReader;

import org.xml.sax.helpers.DefaultHandler;

import android.app.Activity;

import android.os.AsyncTask;

import android.os.Bundle;

import android.os.Handler;

import android.os.Message;

import android.util.Log;

import android.view.View;

import android.widget.Button;

import android.widget.EditText;

import android.widget.ListView;

import android.widget.SimpleAdapter;

public class HtmltestActivity extends Activity {

EditText mUrlText;

//EditText mShowHtml;

ListView mProducts;

Handler mMainHandler;

SimpleAdapter mProdList;

ArrayList<HashMap<String,Object>> mlist;

/** Called when the activity is first created. */

@Override

public void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.main);

mUrlText = (EditText)findViewById(R.id.eturl);

//mShowHtml = (EditText)findViewById(R.id.etshowhtml);

mProducts = (ListView)findViewById(R.id.productList);

Button btn = (Button)findViewById(R.id.btngo);

mlist = new ArrayList<HashMap<String, Object>>();

mProdList = new SimpleAdapter(this,

mlist,

R.layout.listitem,

new String[]{"name", "price"},

new int[]{R.id.prd_title, R.id.prd_price}

);

mProducts.setAdapter(mProdList);

btn.setOnClickListener(new View.OnClickListener() {

@Override

public void onClick(View v) {

// TODO Auto-generated method stub

httpGet();

}

});

mMainHandler = new Handler() {

public void handleMessage(Message msg) {

//mShowHtml.append((String)msg.obj);

if(msg.obj != null) {

ProductInfo prod = (ProductInfo)msg.obj;

Log.i("Prodcut:", prod.toString());

//mShowHtml.append(prod.toString());

HashMap<String, Object> map = new HashMap<String, Object>();

map.put("name", prod.name);

map.put("price", "RMB" + prod.price);

mlist.add(map);

mProdList.notifyDataSetChanged();

}

};

}

void httpGet() {

GetHttpTask task = new GetHttpTask();

task.execute("http://192.168.1.111:8080/nfcdemo/products.xml");

}

public class GetHttpTask extends AsyncTask<String, Integer, String> {

public GetHttpTask() {

}

protected void onPreExecute() {

}

protected String doInBackground(String... params) {

HttpGet httpRequest = new HttpGet(params[0]);

HttpClient httpclient = new DefaultHttpClient();

//mShowHtml.setText("");

try {

HttpResponse httpResponse = httpclient.execute(httpRequest);

if(httpResponse.getStatusLine().getStatusCode() == HttpStatus.SC_OK){

HttpEntity entitiy = httpResponse.getEntity();

InputStream in = entitiy.getContent();

InputSource source = new InputSource(in);

SAXParserFactory sax = SAXParserFactory.newInstance();

XMLReader xmlReader = sax.newSAXParser().getXMLReader();

xmlReader.setContentHandler(new ProductHandler());

xmlReader.parse(source);

}

else {

//return "请求失败!";

//mShowHtml.setText("请求失败");

//Message mymsg = mMainHandler.obtainMessage();

//mymsg.obj = "请求失败";

//mMainHandler.sendMessage(mymsg);

}

}catch(IOException e){

e.printStackTrace();

}catch(SAXException e) {

e.printStackTrace();

}catch(ParserConfigurationException e) {

e.printStackTrace();

}

return null;

}

protected void onPostExecute(String result) {

//mShowHtml.setText(result);

}

class ProductInfo {

public String name;

public float price;

public String image;

public String toString() {

return "\nName:" + name +"\nPrice :" + price + "\nImage:" + image;

}

class ProductHandler extends DefaultHandler {

private ProductInfo curProduct;

private String content;

public void startElement(String uri, String localName, String name, org.xml.sax.Attributes attributes) throws SAXException {

if(localName.equals("product")) {

curProduct = new ProductInfo();

}

else if(localName.equals("image")) {

//set name

curProduct.image = attributes.getValue("src");

}

super.startElement(uri, localName, name, attributes);

}

public void endElement(String uri, String localName, String name) throws SAXException{

if(localName.equals("product")) {

//send event

//get main handler

Message msg = mMainHandler.obtainMessage();

msg.obj = curProduct;

mMainHandler.sendMessage(msg);

//Log.i("Product:", curProduct.toString());

}

else if(localName.equals("name")) {

//set name

curProduct.name = content;

}

else if(localName.equals("price")) {

curProduct.price = Float.parseFloat(content);

}

super.endElement(uri, localName, name);

}

public void characters (char[] ch, int start, int length) throws SAXException

{

content = new String(ch, start, length);

//Log.i("Parser:" ,content);

super.characters(ch, start, length);

}

main.xml

<?xml version="1.0" encoding="utf-8"?>

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"

android:layout_width="fill_parent"

android:layout_height="fill_parent"

android:orientation="vertical" >

<LinearLayout

android:id="@+id/linearLayout1"

android:layout_width="match_parent"

android:layout_height="wrap_content" >

<EditText

android:id="@+id/eturl"

android:layout_width="match_parent"

android:layout_height="wrap_content"

android:layout_weight="1" >

</EditText>

<Button

android:id="@+id/btngo"

android:layout_width="100dp"

android:layout_height="wrap_content"

android:layout_weight="1"

android:text="Go!" />

</LinearLayout>

<ListView

android:id="@+id/productList"

android:layout_width="match_parent"

android:layout_height="match_parent" >

</ListView>

</LinearLayout>

listitem.xml

<?xml version="1.0" encoding="utf-8"?>

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"

android:layout_width="match_parent"

android:layout_height="match_parent" >

<ImageView

android:id="@+id/product_icon"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:layout_alignParentLeft="true"

android:layout_alignParentTop="true"

android:src="@drawable/ic_launcher" />

<TextView

android:id="@+id/prd_title"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:layout_alignParentTop="true"

android:layout_toRightOf="@+id/product_icon"

android:text="TextView" />

<TextView

android:id="@+id/prd_price"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:layout_alignParentRight="true"

android:layout_alignParentTop="true"

android:text="TextView" />

</RelativeLayout>

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