Android（三）数据存储之XML解析技术 2

二、Pull解析技术

       Pull解析技术与Sax解析技术原理相同，但比Sax解析简单，它们的解析速度和占用的资源差不多。Android内部使用的XML解析技术正是Pull，Android官方推荐开发者们使用Pull解析技术。Pull解析技术是第三方开发的开源技术，它同样可以应用于JavaSE开发。下面我们使用Pull解析技术解析XML文件，然后再使用Pull技术生成XML文件。

 

Pull解析XML文档

       1.XML文件

       依然使用上面的books.xml

 

       2.XML文档对应的实体Book

       依然使用上面的Book.java

      

       3.Pull解析XML类

package com.changcheng.androidxml.xml;

 

import java.io.InputStream;

import java.io.Writer;

import java.util.ArrayList;

import java.util.List;

import org.xmlpull.v1.XmlPullParser;

import org.xmlpull.v1.XmlPullParserFactory;

import org.xmlpull.v1.XmlSerializer;

import android.util.Xml;

import com.changcheng.androidxml.entity.Book;

 

public class AndroidPullXML {

 

         public static List<Book> readXML(InputStream inputStream,

                            String inputEncoding) throws Exception {

                   // 创建Pull解析

                   XmlPullParserFactory pullParserFactory = XmlPullParserFactory

                                     .newInstance();

                   XmlPullParser pullParser = pullParserFactory.newPullParser();

                   // 解析XML

                   pullParser.setInput(inputStream, inputEncoding);

                   // 开始

                   int eventType = pullParser.getEventType();

                  

                   List<Book> books = null;

                   Book book = null;

                   while (eventType != XmlPullParser.END_DOCUMENT) {

                            String nodeName = pullParser.getName();

                            switch (eventType) {

                            // 文档开始

                            case XmlPullParser.START_DOCUMENT:

                                     books = new ArrayList<Book>();

                                     break;

                            // 节点开始

                            case XmlPullParser.START_TAG:

                                     if ("book".equals(nodeName)) {

                                               book = new Book();

                                               book.setId(Integer

                                                                 .parseInt(pullParser.getAttributeValue(0)));

                                     } else if ("name".equals(nodeName)) {

                                               book.setName(pullParser.nextText());

                                     } else if ("price".equals(nodeName)) {

                                               book.setPrice(Float.parseFloat(pullParser.nextText()));

                                     }

                                     break;

                            // 节点结束

                            case XmlPullParser.END_TAG:

                                     if ("book".equals(nodeName)) {

                                               books.add(book);

                                               book = null;

                                     }

                                     break;

                            }

                            eventType = pullParser.next();

                   }

                   return books;

         }

}

 

       4.编写测试Pull解析XML类

       在sax测试类TestAndroidXML中添加一个测试方法：

/**

 * 测试Pull解析XML

 * @throws Throwable

 */

public void testAndroidPullReadXML() throws Throwable {

         InputStream file = this.getClass().getClassLoader().getResourceAsStream("books.xml");

         try {

                   List<Book> books = AndroidPullXML.readXML(file, "UTF-8");

                   Log.i(TAG, books.toString());

         } catch (Exception e) {

                   Log.e(TAG, e.toString());

         }

}

 

       5.运行测试

       在outline面板中的testAndroidPullReadXML方法或在TestAndroidXML类的testAndroidPullReadXML方法上右键->Debug As->Android Junit Test。运行结束后在LogCat面板中查看运行结束。

 

Pull生成XML文档

       使用Pull生成上面的books.xml文档。

      

       1.在AndroidPullXML类中添加一个方法：

public static void writeXML(Writer writer, List<Book> books)

                   throws Exception {

         // 创建XML生成器

         XmlSerializer writexml = Xml.newSerializer();

         writexml.setOutput(writer);

         // 生成XML文档

         writexml.startDocument("UTF-8", true);

         writexml.startTag("", "books");

         for (Book book : books) {

                   // name

                   writexml.startTag("", "name");

                   writexml.attribute("", "id", book.getId() + "");

                   writexml.text(book.getName());

                   writexml.endTag("", "name");

                   // price

                   writexml.startTag("", "price");

                   writexml.text(book.getPrice() + "");

                   writexml.endTag("", "price");

         }

         //

         writexml.endTag("", "books");

}

 

       2.编写测试Pull生成XML方法

       在sax测试类TestAndroidXML中添加一个测试方法：

/**

 * 测试Pull生成XML

 * @throws Throwable

 */

public void testAndroidPullWriteXML() throws Throwable {

         // 生成到内存中。（也可以生成到文件中，那就需要定义一个文件输出流。）

         StringWriter writer = new StringWriter();

         // 添加三本书

         List<Book> books = new ArrayList<Book>();

         books.add(new Book(1, "C", 89));

         books.add(new Book(1, "C++", 100));

         books.add(new Book(1, "Java", 87));

         books.add(new Book(1, "JavaEE", 95));

         // 生成XML

         AndroidPullXML.writeXML(writer, books);

         // 打印结果

         Log.i(TAG, books.toString());

 

}

 

       3.运行测试

       在outline面板中的testAndroidPullWriteXML方法或在TestAndroidXML类的testAndroidPullWriteXML方法上右键->Debug As->Android Junit Test。运行结束后在LogCat面板中查看运行结束。

 

       OK，使用Sax和Pull在Android中解析XML文档到此完成。在Andorid中还可以使用DOM技术，使用DOM技术解析在我们学习JavaWeb基础时，已经做了总结，在此就不再介绍了。