HTTP 通信, 三种方式XML 解析,并通过 Hander 实现异步消息处理

本文出自：系出名门Android(10) - HTTP 通信, XML 解析, 通过 Hander 实现异步消息处理

作者：webabcd

介绍

在 Android 中与服务端做 HTTP 通信，解析 XML，通过 Handler 实现异步消息处理

HTTP 通信 - 与服务端做 HTTP 通信，分别以 GET 方式和 POST 方式做演示

XML 解析 - 可以用两种方式解析 XML，分别是 DOM 方式和 SAX 方式

异步消息处理 - 通过 Handler 实现异步消息处理，以一个自定义的异步下载类来说明 Handler 的用法

1、HTTP 通信和 XML 解析的 Demo

MySAXHandler.java

Java代码


代码
package com.webabcd.communication;

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

// 继承 DefaultHandler 以实现指定 XML 的 SAX 解析器
// DOM - W3C 标准，需要把 xml 数据全部加载完成后才能对其做解析，可对树做任意遍历
// SAX - 流式解析，通过事件模型解析 xml，只能顺序解析
public class MySAXHandler extends DefaultHandler {

private boolean mIsTitleTag = false;
private boolean mIsSalaryTag = false;
private boolean mIsBirthTag = false;
private String mResult = "";

// 打开 xml 文档的回调函数
@Override
public void startDocument() throws SAXException {
// TODO Auto-generated method stub
super.startDocument();
}

// 关闭 xml 文档的回调函数
@Override
public void endDocument() throws SAXException {
// TODO Auto-generated method stub
super.endDocument();
}

// 一发现元素开始标记就回调此函数
@Override
public void startElement(String uri, String localName, String qName,
Attributes attributes) throws SAXException {
if (localName == "title")
mIsTitleTag = true;
else if (localName == "salary")
mIsSalaryTag = true;
else if (localName == "dateOfBirth")
mIsBirthTag = true;
else if (localName == "employee")
mResult += "\nname:" + attributes.getValue("name");
}

// 一发现元素结束标记就回调此函数
@Override
public void endElement(String uri, String localName, String qName)
throws SAXException {
if (localName == "title")
mIsTitleTag = false;
else if (localName == "salary")
mIsSalaryTag = false;
else if (localName == "dateOfBirth")
mIsBirthTag = false;
}

// 一发现元素值或属性值就回调此函数
@Override
public void characters(char[] ch, int start, int length)
throws SAXException {
if (mIsTitleTag)
mResult += new String(ch, start, length);
else if (mIsSalaryTag)
mResult += " salary:" + new String(ch, start, length);
else if (mIsBirthTag)
mResult += " dateOfBirth:" + new String(ch, start, length);
}

public String getResult(){
return mResult;
}
}

Main.java

代码
package com.webabcd.communication;

import java.io.BufferedInputStream;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;
import java.net.URLConnection;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Map;

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

import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.client.entity.UrlEncodedFormEntity;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.impl.client.DefaultHttpClient;
import org.apache.http.message.BasicNameValuePair;
import org.apache.http.protocol.HTTP;
import org.apache.http.util.ByteArrayBuffer;
import org.apache.http.util.EncodingUtils;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.NodeList;
import org.xml.sax.InputSource;
import org.xml.sax.XMLReader;

import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;

public class Main extends Activity {

private TextView textView;

/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);

textView = (TextView) this.findViewById(R.id.textView);

Button btn1 = (Button) this.findViewById(R.id.btn1);
btn1.setText("http get demo");
btn1.setOnClickListener(new Button.OnClickListener() {
public void onClick(View v) {
httpGetDemo();
}
});

Button btn2 = (Button) this.findViewById(R.id.btn2);
btn2.setText("http post demo");
btn2.setOnClickListener(new Button.OnClickListener() {
public void onClick(View v) {
httpPostDemo();
}
});

Button btn3 = (Button) this.findViewById(R.id.btn3);
// DOM - Document Object Model
btn3.setText("DOM 解析 XML");
btn3.setOnClickListener(new Button.OnClickListener() {
public void onClick(View v) {
DOMDemo();
}
});

Button btn4 = (Button) this.findViewById(R.id.btn4);
// SAX - Simple API for XML
btn4.setText("SAX 解析 XML");
btn4.setOnClickListener(new Button.OnClickListener() {
public void onClick(View v) {
SAXDemo();
}
});
}

// Android 调用 http 协议的 get 方法
// 本例：以 http 协议的 get 方法获取远程页面响应的内容
private void httpGetDemo(){
try {
// 模拟器测试时，请使用外网地址
URL url = new URL("http://xxx.xxx.xxx");
URLConnection con = url.openConnection();

String result = "http status code: " + ((HttpURLConnection)con).getResponseCode() + "\n";
// HttpURLConnection.HTTP_OK

InputStream is = con.getInputStream();
BufferedInputStream bis = new BufferedInputStream(is);
ByteArrayBuffer bab = new ByteArrayBuffer(32);
int current = 0;
while ( (current = bis.read()) != -1 ){
bab.append((byte)current);
}
result += EncodingUtils.getString(bab.toByteArray(), HTTP.UTF_8);

bis.close();
is.close();

textView.setText(result);
} catch (Exception e) {
textView.setText(e.toString());
}
}

// Android 调用 http 协议的 post 方法
// 本例：以 http 协议的 post 方法向远程页面传递参数，并获取其响应的内容
private void httpPostDemo(){
try {
// 模拟器测试时，请使用外网地址
String url = "http://5billion.com.cn/post.php";
Map<String, String> data = new HashMap<String, String>();
data.put("name", "webabcd");
data.put("salary", "100");

DefaultHttpClient httpClient = new DefaultHttpClient();
HttpPost httpPost = new HttpPost(url);
ArrayList<BasicNameValuePair> postData = new ArrayList<BasicNameValuePair>();
for (Map.Entry<String, String> m : data.entrySet()) {
postData.add(new BasicNameValuePair(m.getKey(), m.getValue()));
}

UrlEncodedFormEntity entity = new UrlEncodedFormEntity(postData, HTTP.UTF_8);
httpPost.setEntity(entity);

HttpResponse response = httpClient.execute(httpPost);

String result = "http status code: " + response.getStatusLine().getStatusCode() + "\n";
// HttpURLConnection.HTTP_OK

HttpEntity httpEntity = response.getEntity();

InputStream is = httpEntity.getContent();
result += convertStreamToString(is);

textView.setText(result);
} catch (Exception e) {
textView.setText(e.toString());
}
}

// 以 DOM 方式解析 XML（xml 数据详见 res/raw/employee.xml）
private void DOMDemo(){
try {
DocumentBuilderFactory docFactory = DocumentBuilderFactory.newInstance();
DocumentBuilder docBuilder = docFactory.newDocumentBuilder();
Document doc = docBuilder.parse(this.getResources().openRawResource(R.raw.employee));
Element rootElement = doc.getDocumentElement();
NodeList employeeNodeList = rootElement.getElementsByTagName("employee");

textView.setText("DOMDemo" + "\n");
String title = rootElement.getElementsByTagName("title").item(0).getFirstChild().getNodeValue();
textView.append(title);
for (int i=0; i<employeeNodeList.getLength(); i++){
Element employeeElement = ((Element)employeeNodeList.item(i));
String name = employeeElement.getAttribute("name");
String salary = employeeElement.getElementsByTagName("salary").item(0).getFirstChild().getNodeValue();
String dateOfBirth = employeeElement.getElementsByTagName("dateOfBirth").item(0).getFirstChild().getNodeValue();
textView.append("\nname: "+name+" salary: "+salary+" dateOfBirth: " + dateOfBirth);
}
} catch (Exception e) {
textView.setText(e.toString());
}
}

// 以 SAX 方式解析 XML（xml 数据详见 res/raw/employee.xml）
// SAX 解析器的实现详见 MySAXHandler.java
private void SAXDemo(){
try {
SAXParserFactory saxFactory = SAXParserFactory.newInstance();
SAXParser parser = saxFactory.newSAXParser();
XMLReader reader = parser.getXMLReader();

MySAXHandler handler = new MySAXHandler();
reader.setContentHandler(handler);
reader.parse(new InputSource(this.getResources().openRawResource(R.raw.employee)));
String result = handler.getResult();
textView.setText("SAXDemo" + "\n");
textView.append(result);
} catch (Exception e) {
textView.setText(e.toString());
}
}

// 辅助方法，用于把流转换为字符串
private String convertStreamToString(InputStream is) {
BufferedReader reader = new BufferedReader(new InputStreamReader(is));
StringBuilder sb = new StringBuilder();

String line = null;
try {
while ((line = reader.readLine()) != null) {
sb.append(line + "\n");
}
} catch (IOException e) {
e.printStackTrace();
} finally {
try {
is.close();
} catch (IOException e) {
e.printStackTrace();
}
}

return sb.toString();
}
}

2、用 Handler 来实现异步消息处理，以一个可以实时汇报下载进度的异步下载类为例
开发一个 Android 类库，本例中此类库名为 webabcd_util

New -> Java Project
项目上点右键 -> Build Path -> Add Libraries -> User Library -> User Libraries -> New -> 为类库起个名字 -> 选中这个类库 -> Add JARs 导入 Android 的 jar 包
项目上点右键 -> Build Path -> Add Libraries -> User Library -> 选择 Android 库

DownloadManagerAsync.java

代码
package webabcd.util;

import java.io.BufferedReader;
import java.io.File;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.URL;
import java.net.URLConnection;

import org.apache.http.protocol.HTTP;

import android.os.Handler;
import android.os.Message;
import android.util.Log;

// 以一个实例，即异步下载，来演示 Android 的异步消息处理（用 Handler 的方式）
public class DownloadManagerAsync {

public DownloadManagerAsync() {

}

// 实例化自定义的 Handler
EventHandler mHandler = new EventHandler(this);

// 按指定 url 地址下载文件到指定路径
public void download(final String url, final String savePath) {
new Thread(new Runnable() {
public void run() {
try {
sendMessage(FILE_DOWNLOAD_CONNECT);
URL sourceUrl = new URL(url);
URLConnection conn = sourceUrl.openConnection();
InputStream inputStream = conn.getInputStream();

int fileSize = conn.getContentLength();

File savefile = new File(savePath);
if (savefile.exists()) {
savefile.delete();
}
savefile.createNewFile();

FileOutputStream outputStream = new FileOutputStream(
savePath, true);

byte[] buffer = new byte[1024];
int readCount = 0;
int readNum = 0;
int prevPercent = 0;
while (readCount < fileSize && readNum != -1) {
readNum = inputStream.read(buffer);
if (readNum > -1) {
outputStream.write(buffer);
readCount = readCount + readNum;

int percent = (int) (readCount * 100 / fileSize);
if (percent > prevPercent) {
// 发送下载进度信息
sendMessage(FILE_DOWNLOAD_UPDATE, percent,
readCount);

prevPercent = percent;
}
}
}

outputStream.close();
sendMessage(FILE_DOWNLOAD_COMPLETE, savePath);

} catch (Exception e) {
sendMessage(FILE_DOWNLOAD_ERROR, e);
Log.e("MyError", e.toString());
}
}
}).start();
}

// 读取指定 url 地址的响应内容
public void download(final String url) {
new Thread(new Runnable() {
public void run() {
try {
sendMessage(FILE_DOWNLOAD_CONNECT);
URL sourceUrl = new URL(url);
URLConnection conn = sourceUrl.openConnection();
conn.setConnectTimeout(3000);
BufferedReader reader = new BufferedReader(
new InputStreamReader(conn.getInputStream(),
HTTP.UTF_8));

String line = null;
StringBuffer content = new StringBuffer();
while ((line = reader.readLine()) != null) {
content.append(line);
}

reader.close();

sendMessage(FILE_DOWNLOAD_COMPLETE, content.toString());

} catch (Exception e) {
sendMessage(FILE_DOWNLOAD_ERROR, e);
Log.e("MyError", e.toString());
}
}
}).start();
}

// 向 Handler 发送消息
private void sendMessage(int what, Object obj) {
// 构造需要向 Handler 发送的消息
Message msg = mHandler.obtainMessage(what, obj);
// 发送消息
mHandler.sendMessage(msg);
}

private void sendMessage(int what) {
Message msg = mHandler.obtainMessage(what);
mHandler.sendMessage(msg);
}

private void sendMessage(int what, int arg1, int arg2) {
Message msg = mHandler.obtainMessage(what, arg1, arg2);
mHandler.sendMessage(msg);
}

private static final int FILE_DOWNLOAD_CONNECT = 0;
private static final int FILE_DOWNLOAD_UPDATE = 1;
private static final int FILE_DOWNLOAD_COMPLETE = 2;
private static final int FILE_DOWNLOAD_ERROR = -1;

// 自定义的 Handler
private class EventHandler extends Handler {
private DownloadManagerAsync mManager;

public EventHandler(DownloadManagerAsync manager) {
mManager = manager;
}

// 处理接收到的消息
@Override
public void handleMessage(Message msg) {

switch (msg.what) {
case FILE_DOWNLOAD_CONNECT:
if (mOnDownloadConnectListener != null)
mOnDownloadConnectListener.onDownloadConnect(mManager);
break;
case FILE_DOWNLOAD_UPDATE:
if (mOnDownloadUpdateListener != null)
mOnDownloadUpdateListener.onDownloadUpdate(mManager,
msg.arg1);
break;
case FILE_DOWNLOAD_COMPLETE:
if (mOnDownloadCompleteListener != null)
mOnDownloadCompleteListener.onDownloadComplete(mManager,
msg.obj);
break;
case FILE_DOWNLOAD_ERROR:
if (mOnDownloadErrorListener != null)
mOnDownloadErrorListener.onDownloadError(mManager,
(Exception) msg.obj);
break;
default:
break;
}
}
}

// 定义连接事件
private OnDownloadConnectListener mOnDownloadConnectListener;
public interface OnDownloadConnectListener {
void onDownloadConnect(DownloadManagerAsync manager);
}
public void setOnDownloadConnectListener(OnDownloadConnectListener listener) {
mOnDownloadConnectListener = listener;
}

// 定义下载进度更新事件
private OnDownloadUpdateListener mOnDownloadUpdateListener;
public interface OnDownloadUpdateListener {
void onDownloadUpdate(DownloadManagerAsync manager, int percent);
}
public void setOnDownloadUpdateListener(OnDownloadUpdateListener listener) {
mOnDownloadUpdateListener = listener;
}

// 定义下载完成事件
private OnDownloadCompleteListener mOnDownloadCompleteListener;
public interface OnDownloadCompleteListener {
void onDownloadComplete(DownloadManagerAsync manager, Object result);
}
public void setOnDownloadCompleteListener(
OnDownloadCompleteListener listener) {
mOnDownloadCompleteListener = listener;
}

// 定义下载异常事件
private OnDownloadErrorListener mOnDownloadErrorListener;
public interface OnDownloadErrorListener {
void onDownloadError(DownloadManagerAsync manager, Exception e);
}
public void setOnDownloadErrorListener(OnDownloadErrorListener listener) {
mOnDownloadErrorListener = listener;
}
}

调用上面的自定义的 Android 类库

项目上点右键 -> Properties -> Java Build Path -> Projects -> Add 引用上面的类库

Main.java

代码
package com.webabcd.handler;

import android.app.Activity;
import android.os.Bundle;
import android.widget.TextView;

import webabcd.util.DownloadManagerAsync;

public class Main extends Activity implements
DownloadManagerAsync.OnDownloadCompleteListener,
DownloadManagerAsync.OnDownloadUpdateListener,
DownloadManagerAsync.OnDownloadErrorListener {

TextView txt;

/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);

DownloadManagerAsync manager = new DownloadManagerAsync();
manager.setOnDownloadCompleteListener(this);
manager.setOnDownloadUpdateListener(this);
manager.download("http://files.cnblogs.com/webabcd/Android.rar", "/sdcard/Android.rar");

txt = (TextView) this.findViewById(R.id.txt);
txt.setText("开始下载");
}

public void onDownloadComplete(DownloadManagerAsync manager, Object result) {

txt.setText("下载完成");
}

public void onDownloadUpdate(DownloadManagerAsync manager, int percent) {

txt.setText("下载进度：" + String.valueOf(percent) + "%");
}

public void onDownloadError(DownloadManagerAsync manager, Exception e) {

txt.setText("下载出错");
}
}