Android 解析XML文件（sax） - Chinaunix

android系统支持使用SAX、DOM或者pull读取xml文件(建议不要使用DOM解析-它比较耗内存)

SAX是一个解析速度快并且占用内存少的xml解析器。它解析的时候采用事件驱动。

即它不需要解析完整个文档，在按内容顺序解析文档的过程中，SAX会判断当前读到的字符是否合法的XML语法的某部分，

如果符合，则会调用某个回调方法——这些方法定义在ContentHandle接口中。

当遇到文档的开头的时候，调用该方法，可以做一些预处理的工作

当文档结束的时候，调用该方法，可以做一些善后工作

startElement(String namespaceURI,String localName,String qName,Attributes attr)

当读到一个开始标签的时候，会触发这个方法

参数分别为：命名空间、不带命名空间的标签名、带命名空间的标签名、得到的所有属性名和相应的值

endElement(String uri,String localName,String name)

在遇到结束标签的时候，调用该方法

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

这个方法来处理在xml文件中读到的内容，第一个参数用于存放文件的内容，后面的两个参数是读到的字符串

在这个数组中的起始位置和长度，使用new String(ch,start,length)就可以获取内容

如有以下xml文件

<?xml version="1.0" encoding="UTF-8"?>

<name>XiaoZhang</name>

解析过程触发的事件为：

读到的标签及内容触发事件

{文档开始} startDocument()

<persons> startElement("","persons",null,"{Attributes}")

"\n\t" characters("<persons>...</persons>","12","2")

<person> startElement("","person",null,"{Attributes}")

"\n\t\t" characters("<persons>...</persons>","31","3")

<name> startElement("","name",null,"{Attributes}")

"LiMing" characters("<persons>...</persons>","40","2")

</name> endElement("","name",null)

"\n\t\t" characters("<persons>...</persons>","50","3")

<age> startElement("","age",null,"{Attributes}")

"30" characters("<persons>...</persons>","58","2")

</age> endElement("","age",null)

"\n\t" characters("<persons>...</persons>","67","2")

</person> endElement("","person",null)

"\n\t" characters("<persons>...</persons>","79","2")

<person> startElement("","person",null,"{Attributes}")

"\n\t\t" characters("<persons>...</persons>","98","3")

<name> startElement("","name",null,"{Attributes}")

"XiaoZhang" characters("<persons>...</persons>","107","3")

</name> endElement("","name",null)

"\n\t\t" characters("<persons>...</persons>","118","3")

<age> startElement("","age",null,"{Attributes}")

"25" characters("<persons>...</persons>","126","2")

</age> endElement("","age",null)

"\n\t\t" characters("<persons>...</persons>","135","2")

</person> endElement("","person",null)

"\n" characters("<persons>...</persons>","147","1")

</persons> endElement

写了一个sax解析程序，来解析该xml文件

import org.xml.sax.Attributes;
import org.xml.sax.SAXException;
import org.xml.sax.helpers.DefaultHandler;
public class StudentInfoContentHandler2 extends DefaultHandler {
@Override
public void characters(char[] ch, int start, int length) throws SAXException {
if(person!=null) {
String data = new String(ch, start, length);
if("name".equals(tagName)) {
person.name = data;
} else if("age".equals(tagName)) {
person.age = Integer.valueOf(data);
}
}
}
@Override
public void endDocument() throws SAXException {
for(Person p : personList) {
System.out.println(p);
}
}
@Override
public void endElement(String uri, String localName, String qName) throws SAXException {
if("person".equals(qName)) {
personList.add(person);
person = null;
}
tagName = null;
}
@Override
public void startDocument() throws SAXException {
personList = new ArrayList<Person>();
}
@Override
public void startElement(String uri, String localName, String qName, Attributes attributes) throws SAXException {
if("person".equals(qName)) {
person = new Person();
person.id = Integer.valueOf(attributes.getValue("id"));
} else {
}
tagName = qName;
}
List<Person> personList;
Person person;
String tagName;
}
class Person
{
@Override
public String toString() {
return "id=" + id + " name=" + name + " age=" + age;
}
public int id;
public String name;
public int age;
}

写了一个测试程序，来测试解析过程是否正确：

import java.io.File;
import java.io.IOException;
import javax.xml.parsers.ParserConfigurationException;
import javax.xml.parsers.SAXParser;
import javax.xml.parsers.SAXParserFactory;
import org.xml.sax.SAXException;
public class SAX_XML_Parser {
public static void main(String[] args) {
try {
readXml();
} catch (ParserConfigurationException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (SAXException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
private static void readXml() throws ParserConfigurationException, SAXException, IOException {
File file = new File("C:/studentInfo.xml");
SAXParserFactory spf = SAXParserFactory.newInstance();
SAXParser saxParser = spf.newSAXParser();
//saxParser.setProperty("http://xml.org/sax/features/namespaces", true);
StudentInfoContentHandler2 handler = new StudentInfoContentHandler2();
saxParser.parse(file, handler);
}
}

id=10 name=LiMing age=25

id=20 name=XiaoZhang age=30