Pull解析XML文件

PULL解析器的运行方式是基于事件的解析模式。在PULL解析过程中，我们需要自己获取产生的事件然后做相应的操作。PULL解析器小巧轻便，解析速度快，简单易用，非常适合在Android移动设备中使用，Android系统内部在解析各种XML时也是用PULL解析器。

Demo链接：http://download.csdn.net/detail/l_lhc/9298283

使用PULL解析器解析和生成XML文件：

Step 1 : 在项目的assets目录中放置一个XML文档books.xml，内容如下：

<?xml version="1.0" encoding="utf-8"?>
<books>
<book id="10001" ps="First">
<name>Thinking In Java</name>
<price>80.00</price>
</book>
<book id="10002" ps="Second">
<name>Core Java</name>
<price>90.00</price>
</book>
<book id="10003" ps="Third">
<name>Hello, Andriod</name>
<price>100.00</price>
</book>
</books>

Step 2 : 创建一个List的对象，先来看一下Book.java的代码：

package com.lhc.xmlparser.bean;
public class Book {
private int id;//编号
private String ps;//名次
private String name;//书名
private float price;//价格
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getPs() {
return ps;
}
public void setPs(String ps) {
this.ps = ps;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public float getPrice() {
return price;
}
public void setPrice(float price) {
this.price = price;
}

@Override
public String toString() {
return "id:" + id  + ", ps:" + ps + ", name:" + name + ", price:" + price;
}
}

Step 3 : 我们先为解析器定义一个BookParser接口，每种类型的解析器需要实现此接口。BookParser.java代码如下：

package com.lhc.xmlparser.parser;
import java.io.InputStream;
import java.util.List;
import com.lhc.xmlparser.bean.Book;
public interface BookParser {
/**
* 解析输入流 得到Book对象集合
* @param is
* @return
* @throws Exception
*/
public List<Book> parse(InputStream is) throws Exception;

/**
* 序列化Book对象集合 得到XML形式的字符串(用于生成新的xml文件)
* @param books
* @return
* @throws Exception
*/
public String serialize(List<Book> books) throws Exception;
}

Step 4 : 创建一个实现BookParser接口的解析器PullBookParser.java。

1.取得节点的值

//第一种方式
eventType = parser.next();
parser.getText();

//第二种方式
parser.nextText();

2.取得节点括号内属性的值

//第一种方式（获取属性"PS"的值）
parser.getAttributeValue(null,"ps");

//第二种方式（获取第index位置属性的值）
parser.getAttributeValue(index);

PullBookParser.java代码如下：

package com.lhc.xmlparser.parser;
import java.io.InputStream;
import java.util.List;
import com.lhc.xmlparser.bean.Book;
import java.io.StringWriter;
import java.util.ArrayList;
import org.xmlpull.v1.XmlPullParser;
import org.xmlpull.v1.XmlSerializer;
import android.util.Xml;
public class PullBookParser implements BookParser {
@Override
public List<Book> parse(InputStream is) throws Exception {
List<Book> books = null;
Book book = null;
XmlPullParser parser = Xml.newPullParser(); //由android.util.Xml创建一个XmlPullParser实例
parser.setInput(is, "UTF-8");               //设置输入流 并指明编码方式
int eventType = parser.getEventType();
while (eventType != XmlPullParser.END_DOCUMENT) {
switch (eventType) {
case XmlPullParser.START_DOCUMENT://文档开头
books = new ArrayList<Book>();
break;
case XmlPullParser.START_TAG://节点开头
if (parser.getName().equals("book")) {
book = new Book();
int id = Integer.parseInt(parser.getAttributeValue(null,"id"));
//int id = Integer.parseInt(parser.getAttributeValue(0));
book.setId(id);
String ps = String.valueOf(parser.getAttributeValue(null,"ps"));
//String ps = String.valueOf(parser.getAttributeValue(1));
book.setPs(ps);
} else if (parser.getName().equals("name")) {
eventType = parser.next();
book.setName(parser.getText());
//book.setName(parser.nextText());
} else if (parser.getName().equals("price")) {
eventType = parser.next();
book.setPrice(Float.parseFloat(parser.getText()));
//book.setPrice(parser.nextText());
}
break;
case XmlPullParser.END_TAG://节点结束
if (parser.getName().equals("book")) {
books.add(book);
book = null;
}
break;
}
eventType = parser.next();
}
return books;
}

@Override
public String serialize(List<Book> books) throws Exception {
XmlSerializer serializer = Xml.newSerializer(); //由android.util.Xml创建一个XmlSerializer实例
StringWriter writer = new StringWriter();
serializer.setOutput(writer);   //设置输出方向为writer
serializer.startDocument("UTF-8", true);
serializer.startTag("", "books");
for (Book book : books) {
serializer.startTag("", "book");
serializer.attribute("", "id", book.getId() + "");
serializer.startTag("", "name");
serializer.text(book.getName());
serializer.endTag("", "name");
serializer.startTag("", "price");
serializer.text(book.getPrice() + "");
serializer.endTag("", "price");
serializer.endTag("", "book");
}
serializer.endTag("", "books");
serializer.endDocument();
return writer.toString();
}
}

Step 5 : 在MainActivity.java中完成调用。MainActivity.java代码如下：

package com.lhc.xmlparser;
import java.io.File;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.io.OutputStreamWriter;
import java.io.Writer;
import java.util.List;
import com.lhc.xmlparser.bean.Book;
import com.lhc.xmlparser.parser.BookParser;
import com.lhc.xmlparser.parser.PullBookParser;
import android.app.Activity;
import android.os.Bundle;
import android.os.Environment;
import android.util.Log;
import android.view.View;
import android.widget.Button;
public class MainActivity extends Activity {
private static final String TAG = "XML";
private BookParser parser;
private List<Book> books;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Button readBtn = (Button) findViewById(R.id.btn_read);
Button writeBtn = (Button) findViewById(R.id.btn_write);
readBtn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
try {
InputStream is = getAssets().open("books.xml");
parser = new PullBookParser();  //创建SaxBookParser实例
books = parser.parse(is);  //解析输入流
for (Book book : books) {
Log.i(TAG, book.toString());
}
} catch (Exception e) {
Log.e(TAG, e.getMessage());
}
}
});
writeBtn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
try {
String xml = parser.serialize(books);  //序列化

File sdCard = Environment.getExternalStorageDirectory();
sdCard = new File(sdCard, "/MyFiles");
sdCard.mkdirs();// 创建MyFiles目录(可创建多级目录)
sdCard = new File(sdCard, "books.xml");
FileOutputStream out = new FileOutputStream(sdCard);
Writer writer = new OutputStreamWriter(out);
try {
writer.write(xml);
} finally {
writer.close();
}

} catch (Exception e) {
Log.e(TAG, e.getMessage());
}
}
});
}
}

Step 6: 若要写入文件到SD卡中则需要在AndroidManifest.xml配置一下权限：

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
<uses-permission android:name="android.permission.MOUNT_UNMOUNT_FILESYSTEMS"/>