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

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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 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 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 data = new HashMap();
                        data.put("name", "webabcd");
                        data.put("salary", "100");

                        DefaultHttpClient httpClient = new DefaultHttpClient();
                        HttpPost httpPost = new HttpPost(url);
                        ArrayList postData = new ArrayList();
                        for (Map.Entry 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                                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 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 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");
        }
}

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

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