系出名門Android(10) - HTTP 通信, XML 解析, 通過 Hander 實作異步消息處理

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介紹

在 Android 中與服務端做 HTTP 通信，解析 XML，通過 Handler 實作異步消息處理

HTTP 通信 - 與服務端做 HTTP 通信，分别以 GET 方式和 POST 方式做示範

XML 解析 - 可以用兩種方式解析 XML，分别是 DOM 方式和 SAX 方式

異步消息處理 - 通過 Handler 實作異步消息處理，以一個自定義的異步下載下傳類來說明 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;

// 繼承 DefaultHandler 以實作指定 XML 的 SAX 解析器

// DOM - W3C 标準，需要把 xml 資料全部加載完成後才能對其做解析，可對樹做任意周遊

// SAX - 流式解析，通過事件模型解析 xml，隻能順序解析

public class MySAXHandler extends DefaultHandler {

private boolean mIsTitleTag = false;

private boolean mIsSalaryTag = false;

private boolean mIsBirthTag = false;

private String mResult = "";

// 打開 xml 文檔的回調函數

@Override

public void startDocument() throws SAXException {

// TODO Auto-generated method stub

super.startDocument();

}

// 關閉 xml 文檔的回調函數

public void endDocument() throws SAXException {

super.endDocument();

// 一發現元素開始标記就回調此函數

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");

// 一發現元素結束标記就回調此函數

public void endElement(String uri, String localName, String qName)

throws SAXException {

mIsTitleTag = false;

mIsSalaryTag = false;

mIsBirthTag = false;

// 一發現元素值或屬性值就回調此函數

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

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

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. */

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() {

httpPostDemo();

Button btn3 = (Button) this.findViewById(R.id.btn3);

// DOM - Document Object Model

btn3.setText("DOM 解析 XML");

btn3.setOnClickListener(new Button.OnClickListener() {

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() {

SAXDemo();

// Android 調用 http 協定的 get 方法

// 本例：以 http 協定的 get 方法擷取遠端頁面響應的内容

private void httpGetDemo(){

try {

// 模拟器測試時，請使用外網位址

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 調用 http 協定的 post 方法

// 本例：以 http 協定的 post 方法向遠端頁面傳遞參數，并擷取其響應的内容

private void httpPostDemo(){

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";

HttpEntity httpEntity = response.getEntity();

InputStream is = httpEntity.getContent();

result += convertStreamToString(is);

textView.setText(e.toString());

// 以 DOM 方式解析 XML（xml 資料詳見 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);

// 以 SAX 方式解析 XML（xml 資料詳見 res/raw/employee.xml）

// SAX 解析器的實作詳見 MySAXHandler.java

private void SAXDemo(){

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);

// 輔助方法，用于把流轉換為字元串

private String convertStreamToString(InputStream is) {

BufferedReader reader = new BufferedReader(new InputStreamReader(is));

StringBuilder sb = new StringBuilder();

String line = null;

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 來實作異步消息處理，以一個可以實時彙報下載下傳進度的異步下載下傳類為例

開發一個 Android 類庫，本例中此類庫名為 webabcd_util

New -> Java Project

項目上點右鍵 -> Build Path -> Add Libraries -> User Library -> User Libraries -> New -> 為類庫起個名字 -> 選中這個類庫 -> Add JARs 導入 Android 的 jar 包

項目上點右鍵 -> Build Path -> Add Libraries -> User Library -> 選擇 Android 庫

DownloadManagerAsync.java

package webabcd.util;

import java.io.File;

import java.io.FileOutputStream;

import android.os.Handler;

import android.os.Message;

import android.util.Log;

// 以一個執行個體，即異步下載下傳，來示範 Android 的異步消息處理（用 Handler 的方式）

public class DownloadManagerAsync {

public DownloadManagerAsync() {

// 執行個體化自定義的 Handler

EventHandler mHandler = new EventHandler(this);

// 按指定 url 位址下載下傳檔案到指定路徑

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) {

// 發送下載下傳進度資訊

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();

// 讀取指定 url 位址的響應内容

public void download(final String url) {

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());

// 向 Handler 發送消息

private void sendMessage(int what, Object obj) {

// 構造需要向 Handler 發送的消息

Message msg = mHandler.obtainMessage(what, obj);

// 發送消息

mHandler.sendMessage(msg);

private void sendMessage(int what) {

Message msg = mHandler.obtainMessage(what);

private void sendMessage(int what, int arg1, int arg2) {

Message msg = mHandler.obtainMessage(what, arg1, arg2);

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;

// 自定義的 Handler

private class EventHandler extends Handler {

private DownloadManagerAsync mManager;

public EventHandler(DownloadManagerAsync manager) {

mManager = manager;

// 處理接收到的消息

@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);

case FILE_DOWNLOAD_COMPLETE:

if (mOnDownloadCompleteListener != null)

mOnDownloadCompleteListener.onDownloadComplete(mManager,

msg.obj);

case FILE_DOWNLOAD_ERROR:

if (mOnDownloadErrorListener != null)

mOnDownloadErrorListener.onDownloadError(mManager,

(Exception) msg.obj);

default:

// 定義連接配接事件

private OnDownloadConnectListener mOnDownloadConnectListener;

public interface OnDownloadConnectListener {

void onDownloadConnect(DownloadManagerAsync manager);

public void setOnDownloadConnectListener(OnDownloadConnectListener listener) {

mOnDownloadConnectListener = listener;

// 定義下載下傳進度更新事件

private OnDownloadUpdateListener mOnDownloadUpdateListener;

public interface OnDownloadUpdateListener {

void onDownloadUpdate(DownloadManagerAsync manager, int percent);

public void setOnDownloadUpdateListener(OnDownloadUpdateListener listener) {

mOnDownloadUpdateListener = listener;

// 定義下載下傳完成事件

private OnDownloadCompleteListener mOnDownloadCompleteListener;

public interface OnDownloadCompleteListener {

void onDownloadComplete(DownloadManagerAsync manager, Object result);

public void setOnDownloadCompleteListener(

OnDownloadCompleteListener listener) {

mOnDownloadCompleteListener = listener;

// 定義下載下傳異常事件

private OnDownloadErrorListener mOnDownloadErrorListener;

public interface OnDownloadErrorListener {

void onDownloadError(DownloadManagerAsync manager, Exception e);

public void setOnDownloadErrorListener(OnDownloadErrorListener listener) {

mOnDownloadErrorListener = listener;

調用上面的自定義的 Android 類庫

項目上點右鍵 -> Properties -> Java Build Path -> Projects -> Add 引用上面的類庫

package com.webabcd.handler;

import webabcd.util.DownloadManagerAsync;

public class Main extends Activity implements

DownloadManagerAsync.OnDownloadCompleteListener,

DownloadManagerAsync.OnDownloadUpdateListener,

DownloadManagerAsync.OnDownloadErrorListener {

TextView txt;

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("開始下載下傳");

public void onDownloadComplete(DownloadManagerAsync manager, Object result) {

txt.setText("下載下傳完成");

public void onDownloadUpdate(DownloadManagerAsync manager, int percent) {

txt.setText("下載下傳進度：" + String.valueOf(percent) + "%");

public void onDownloadError(DownloadManagerAsync manager, Exception e) {

txt.setText("下載下傳出錯");

本文轉自webabcd 51CTO部落格，原文連結：http://blog.51cto.com/webabcd/342102，如需轉載請自行聯系原作者

系出名門Android(10) - HTTP 通信, XML 解析, 通過 Hander 實作異步消息處理

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