学步园

大家好今天我今天给大家讲解一下android中xml的创建以及一些解析xml的常用方法。

首先是创建，我们用XmlSerializer这个类来创建一个xml文件，其次是解析xml文件，常用的有dom,sax,XmlPullParser等方法，由于sax代码有点复杂，本节只讲解一下dom与XmlPullParser解析，sax我将会在下一节单独讲解,至于几种解析xml的优缺点我就不再讲述了。

为了方便理解，我做了一个简单的Demo。首先首界面有三个按钮，点击第一个按钮会在sdcard目录下创建一个books.xml文件,另外两个按钮分别是调用dom与XmlPullParser方法解析xml文件，并将结果显示在一个TextView里。大家可以按照我的步骤一步步来:

第一步:新建一个Android工程,命名为XmlDemo.

第二步:修改main.xml布局文件，代码如下:

<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:orientation="vertical" android:layout_width="fill_parent" android:layout_height="fill_parent" ><Buttonandroid:id="@+id/btn1"android:layout_width="fill_parent" android:layout_height="wrap_content" android:text="创建XML文件"/><Buttonandroid:id="@+id/btn2"android:layout_width="fill_parent" android:layout_height="wrap_content" android:text="DOM解析XML"/><Buttonandroid:id="@+id/btn3"android:layout_width="fill_parent" android:layout_height="wrap_content" android:text="XmlPullParse解析XML"/><TextViewandroid:id="@+id/result"android:layout_width="fill_parent" android:layout_height="wrap_content" /></LinearLayout>

第三步:修改主核心程序XmlDemo.java,代码如下:

package com.tutor.xml;import java.io.File;import java.io.FileNotFoundException;import java.io.FileOutputStream;import java.io.IOException;import javax.xml.parsers.DocumentBuilder;import javax.xml.parsers.DocumentBuilderFactory;import javax.xml.parsers.ParserConfigurationException;import org.w3c.dom.Document;import org.w3c.dom.Element;import org.w3c.dom.NodeList;import org.xml.sax.SAXException;import org.xmlpull.v1.XmlPullParser;import org.xmlpull.v1.XmlPullParserException;import org.xmlpull.v1.XmlPullParserFactory;import org.xmlpull.v1.XmlSerializer;import android.app.Activity;import android.os.Bundle;import android.util.Log;import android.util.Xml;import android.view.View;import android.view.View.OnClickListener;import android.widget.Button;import android.widget.TextView;import android.widget.Toast;public class XmlDemo extends Activity implements OnClickListener { private static final String BOOKS_PATH = "/sdcard/books.xml";private Button mButton1,mButton2,mButton3;private TextView mTextView; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); setupViews(); } //初始化工作 private void setupViews(){ mTextView = (TextView)findViewById(R.id.result); mButton1 = (Button)findViewById(R.id.btn1); mButton2 = (Button)findViewById(R.id.btn2); mButton3 = (Button)findViewById(R.id.btn3); mButton1.setOnClickListener(this); mButton2.setOnClickListener(this); mButton3.setOnClickListener(this); } //创建xml文件 private void createXmlFile(){ File linceseFile = new File(BOOKS_PATH); try{ linceseFile.createNewFile(); }catch (IOException e) { Log.e("IOException", "exception in createNewFile() method");} FileOutputStream fileos = null; try{ fileos = new FileOutputStream(linceseFile); }catch (FileNotFoundException e) { Log.e("FileNotFoundException", "can't create FileOutputStream");} XmlSerializer serializer = Xml.newSerializer(); try { serializer.setOutput(fileos,"UTF-8"); serializer.startDocument(null, true); serializer.startTag(null, "books"); for(int i = 0; i < 3; i ++){ serializer.startTag(null, "book"); serializer.startTag(null, "bookname"); serializer.text("Android教程" + i); serializer.endTag(null, "bookname"); serializer.startTag(null, "bookauthor"); serializer.text("Frankie" + i); serializer.endTag(null, "bookauthor"); serializer.endTag(null, "book"); } serializer.endTag(null, "books"); serializer.endDocument(); serializer.flush(); fileos.close(); } catch (Exception e) { Log.e("Exception","error occurred while creating xml file"); } Toast.makeText(getApplicationContext(), "创建xml文件成功!", Toast.LENGTH_SHORT).show(); } //dom解析xml文件 private void domParseXML(){ File file = new File(BOOKS_PATH); DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance(); DocumentBuilder db = null; try {db = dbf.newDocumentBuilder();} catch (ParserConfigurationException e) {e.printStackTrace();}Document doc = null;try {doc = db.parse(file);} catch (SAXException e) {e.printStackTrace();} catch (IOException e) {e.printStackTrace();}Element root = doc.getDocumentElement();NodeList books = root.getElementsByTagName("book");String res = "本结果是通过dom解析:" + "/n";for(int i = 0; i < books.getLength();i++){Element book = (Element)books.item(i);Element bookname = (Element)book.getElementsByTagName("bookname").item(0);Element bookauthor = (Element)book.getElementsByTagName("bookauthor").item(0);res += "书名: " + bookname.getFirstChild().getNodeValue() + " " + "作者: " + bookauthor.getFirstChild().getNodeValue() + "/n";}mTextView.setText(res); } //xmlPullParser解析xml文件 private void xmlPullParseXML(){ String res = "本结果是通过XmlPullParse解析:" + "/n"; try { XmlPullParserFactory factory = XmlPullParserFactory.newInstance();XmlPullParser xmlPullParser = factory.newPullParser();xmlPullParser.setInput(Thread.currentThread().getContextClassLoader().getResourceAsStream(BOOKS_PATH), "UTF-8");int eventType = xmlPullParser.getEventType();try{while (eventType != XmlPullParser.END_DOCUMENT) {String nodeName = xmlPullParser.getName();switch (eventType) {case XmlPullParser.START_TAG:if("bookname".equals(nodeName)){res += "书名: " + xmlPullParser.nextText() + " ";}else if("bookauthor".equals(nodeName)){res += "作者: " + xmlPullParser.nextText() + "/n";}break;default:break;}eventType = xmlPullParser.next();}} catch (IOException e) {e.printStackTrace();}} catch (XmlPullParserException e) {e.printStackTrace();}mTextView.setText(res); } //按钮事件响应public void onClick(View v) {if(v == mButton1){createXmlFile();}else if(v == mButton2){domParseXML();}else if(v == mButton3){xmlPullParseXML();}}}

第四步:由于我们在Sd卡上新建了文件，需要增加权限，如下代码(第16行):

<?xml version="1.0" encoding="utf-8"?><manifest xmlns:android="http://schemas.android.com/apk/res/android" package="com.tutor.xml" android:versionCode="1" android:versionName="1.0"> <application android:icon="@drawable/icon" android:label="@string/app_name"> <activity android:name=".XmlDemo" android:label="@string/app_name"> <intent-filter> <action android:name="android.intent.action.MAIN" /> <category android:name="android.intent.category.LAUNCHER" /> </intent-filter> </activity> </application> <uses-sdk android:minSdkVersion="7" /><uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" /> </manifest>

第五步:运行上述工程，查看效果:

启动首界面:

点击创建XML文件按钮,生成books.xml文件

books.xml内容如下:

<?xml version='1.0' encoding='UTF-8' standalone='yes' ?><books> <book> <bookname>Android教程0</bookname> <bookauthor>Frankie0</bookauthor> </book> <book> <bookname>Android教程1</bookname> <bookauthor>Frankie1</bookauthor> </book> <book> <bookname>Android教程2</bookname> <bookauthor>Frankie2</bookauthor> </book></books>

点击DOM解析XML按钮:

点击XmlPullParse解析XML按钮: