Android开发入门之采用Pull解析器解析和生成XML内容

Pull简介

常见的XML解析方式有三种，DOM，SAX，Pull，Android系统中推荐使用Pull

Pull解析器是一个开源的Java项目，Android系统内部解析XML文件均为此种方式，也可用于J2EE项目

Android SDK中已经集成了Pull解析器，无需添加任何jar文件

Pull解析器运行方式与SAX类似，提供各种事件的判断

官方网站：http://xmlpull.org/

使用XmlPullParser解析XML文件

Xml.newPullParser()获得解析器

parser.setInput(in, "UTF-8")设置输入流以及编码

parser.next()获取下一个解析事件，得到一个事件代码

XmlPullParser中定义了常量来标识各种解析事件

   START DOCUMENT             START_TAG           TEXT          END_TAG           END_DOCUMENT

使用XmlSerializer写出XML

使用以下方法生成XML,和XML文档顺序类似

startDocument

startTag

attribute

text

endTag

endDocument

第一步：新建一个Android工程命名为xml目录结构如下图：



person.xml文件放在src目录下：

<?xml version="1.0" encoding="UTF-8"?>
<persons>
<person id="23">
<name>gaolei</name>
<age>23</age>
</person>
<person id="24">
<name>xiaoqiang</name>
<age>25</age>
</person>
</persons>

第二步：编写Person实体类如下：

package cn.leigo.domain;

public class Person {
private Integer id;
private String name;
private Integer age;

public Person() {
}

public Person(Integer id, String name, Integer age) {
this.id = id;
this.name = name;
this.age = age;
}

public Integer getId() {
return id;
}

public void setId(Integer id) {
this.id = id;
}

public String getName() {
return name;
}

public void setName(String name) {
this.name = name;
}

public Integer getAge() {
return age;
}

public void setAge(Integer age) {
this.age = age;
}

@Override
public String toString() {
return "Person [id=" + id + ", name=" + name + ", age=" + age + "]";
}

}

第三步：编写PersonService类来解析和生成Xml：

package cn.leigo.service;

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.ArrayList;
import java.util.List;

import org.xmlpull.v1.XmlPullParser;
import org.xmlpull.v1.XmlPullParserException;
import org.xmlpull.v1.XmlSerializer;

import android.util.Xml;

import cn.leigo.domain.Person;

public class PersonService {

/**
* 获取数据
*
* @param in
* @return
* @throws XmlPullParserException
* @throws IOException
*/
public static List<Person> parser(InputStream in)
throws XmlPullParserException, IOException {
List<Person> persons = null;
Person person = null;
XmlPullParser parser = Xml.newPullParser();
parser.setInput(in, "UTF-8");
int eventType = parser.getEventType();
while (eventType != XmlPullParser.END_DOCUMENT) {
switch (eventType) {
case XmlPullParser.START_DOCUMENT:
persons = new ArrayList<Person>();
break;
case XmlPullParser.START_TAG:
if ("person".equals(parser.getName())) {
person = new Person();
String id = parser.getAttributeValue(0);
person.setId(Integer.valueOf(id));
} else if ("name".equals(parser.getName())) {
String name = parser.nextText();
person.setName(name);
} else if ("age".equals(parser.getName())) {
String age = parser.nextText();
person.setAge(Integer.parseInt(age));
}
break;
case XmlPullParser.END_TAG:
if ("person".equals(parser.getName())) {
persons.add(person);
person = null;
}
break;
}
eventType = parser.next();
}
return persons;
}

/**
* 保存数据
*
* @param persons
*            数据
* @param os
*            输出方向
* @throws IllegalArgumentException
* @throws IllegalStateException
* @throws IOException
*/
public static void serializer(List<Person> persons, OutputStream os)
throws IllegalArgumentException, IllegalStateException, IOException {
XmlSerializer serializer = Xml.newSerializer();
serializer.setOutput(os, "UTF-8");
serializer.startDocument("UTF-8", true);
serializer.startTag(null, "persons");

for (Person person : persons) {
serializer.startTag(null, "person");
serializer.attribute(null, "id", person.getId() + "");

serializer.startTag(null, "name");
serializer.text(person.getName());
serializer.endTag(null, "name");

serializer.startTag(null, "age");
serializer.text(person.getAge() + "");
serializer.endTag(null, "age");

serializer.endTag(null, "person");
}

serializer.endTag(null, "persons");
serializer.endDocument();
os.flush();
os.close();
}
}

最后在添加一个测试类：

package cn.leigo.test;

import java.io.FileOutputStream;
import java.io.InputStream;
import java.util.ArrayList;
import java.util.List;

import android.content.Context;
import android.test.AndroidTestCase;
import android.util.Log;
import cn.leigo.domain.Person;
import cn.leigo.service.PersonService;

public class PersonServiceTest extends AndroidTestCase {
private static final String TAG = "PersonServiceTest";

public void testPersons() throws Exception {
InputStream in = this.getClass().getClassLoader()
.getResourceAsStream("person.xml");
List<Person> persons = PersonService.parser(in);
for (Person person : persons) {
Log.i(TAG, person.toString());
}
}

public void testSave() throws Exception {
List<Person> persons = new ArrayList<Person>();
persons.add(new Person(1, "zhangsan", 24));
persons.add(new Person(2, "lisi", 35));
persons.add(new Person(3, "wangwu", 43));
FileOutputStream fos = getContext().openFileOutput("persons.xml",
Context.MODE_PRIVATE);
PersonService.serializer(persons, fos);
}
}

运行工程查看效果图：

解析Xml



生成Xml



生成的xml文件如下：

<?xml version='1.0' encoding='UTF-8' standalone='yes' ?>
<persons>
<person id="1">
<name>zhangsan</name>
<age>24</age>
</person>
<person id="2">
<name>lisi</name>
<age>35</age>
</person>
<person id="3">
<name>wangwu</name>
<age>43</age>
</person>
</persons>