Android笔记（四十六） Android中的数据存储——XML（二）PULL解析

PULL 的工作原理： 

         XML pull提供了开始元素和结束元素。当某个元素开始时，可以调用parser．nextText()从XML文档中提取所有字符数据。当解析到一个文档结束时，自动生成EndDocument事件。 

类和接口	功能
XmlPullParser	该解析器是一个在org.xmlpull.v1中定义的解析功能的接口。
XmlSerializer	它是一个接口，定义了XML信息集的序列。
XmlPullParserFactory	这个类用于在XMPULL V1 API中创建XML Pull解析器。
XmlPullParserException	抛出单一的XML pull解析器相关的错误。

         它提供了类似的事件，如：开始元素和结束元素事件，使用parser.next()可以进入下一个元素并触发相应事件。事件将作为数值代码被发送，因此可以使用一个switch对感兴趣的事件进行处理。当元素开始解析时，调用parser.nextText()方法可以获取下一个Text类型元素的值。

         读取到xml的声明返回 START_DOCUMENT

         结束返回 END_DOCUMENT  

         开始标签返回 START_TAG 

         结束标签返回 END_TAG 

         示例：

MainActivity.java

package cn.lixyz.xmltest.activity;

import java.util.List;

import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import cn.lixyz.xmltest.R;
import cn.lixyz.xmltest.model.Student;
import cn.lixyz.xmltest.parser.DOMForXML;
import cn.lixyz.xmltest.parser.PULLForXML;
import cn.lixyz.xmltest.parser.SAXForXML;

public class MainActivity extends Activity {

    private Button bt_readxml_dom, bt_writexml_dom, bt_writexml_sax, bt_readxml_sax, bt_readxml_pull, bt_writexml_pull;

    private List<Student> list;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        findView();
    }

    private void findView() {
        bt_readxml_dom = (Button) findViewById(R.id.bt_readxml_dom);
        bt_writexml_dom = (Button) findViewById(R.id.bt_writexml_dom);
        bt_writexml_sax = (Button) findViewById(R.id.bt_writexml_sax);
        bt_readxml_sax = (Button) findViewById(R.id.bt_readxml_sax);
        bt_readxml_pull = (Button) findViewById(R.id.bt_readxml_pull);
        bt_writexml_pull = (Button) findViewById(R.id.bt_writexml_pull);
    }

    public void clickButton(View view) {
        DOMForXML domForXML;
        SAXForXML saxForXML;
        PULLForXML pullForXML;
        switch (view.getId()) {
        case R.id.bt_readxml_dom:
            domForXML = new DOMForXML();
            domForXML.domReadXML();
            break;

        case R.id.bt_writexml_dom:
            domForXML = new DOMForXML();
            domForXML.domWriterXML();
            break;
        case R.id.bt_readxml_sax:
            saxForXML = new SAXForXML();
            saxForXML.saxReaderXML();
            break;
        case R.id.bt_writexml_sax:
            saxForXML = new SAXForXML();
            saxForXML.saxWriterXML();
            break;
        case R.id.bt_writexml_pull:
            pullForXML = new PULLForXML();
            pullForXML.pullWriterXML();
            break;
        case R.id.bt_readxml_pull:
            pullForXML = new PULLForXML();
            pullForXML.pullReaderXML();
            break;
        }
    }

}

activity_main.xml

<ScrollView xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent" >

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical"
        tools:context="cn.lixyz.xmltest.activity.MainActivity" >

        <Button
            android:id="@+id/bt_writexml_dom"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:onClick="clickButton"
            android:text="DOM方式生成XML" />

        <Button
            android:id="@+id/bt_readxml_dom"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:onClick="clickButton"
            android:text="DOM方式读取XML" />

        <Button
            android:id="@+id/bt_writexml_sax"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:onClick="clickButton"
            android:text="SAX方式生成XML" />

        <Button
            android:id="@+id/bt_readxml_sax"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:onClick="clickButton"
            android:text="SAX方式读取XML" />

        <Button
            android:id="@+id/bt_writexml_pull"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:onClick="clickButton"
            android:text="PULL生成XML" />

        <Button
            android:id="@+id/bt_readxml_pull"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:onClick="clickButton"
            android:text="PULL解析XML" />
    </LinearLayout>

</ScrollView>

PULLForXML.java

package cn.lixyz.xmltest.parser;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
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.Log;
import android.util.Xml;
import cn.lixyz.xmltest.model.Student;

public class PULLForXML {

    // pull生成xml文件
    public void pullWriterXML() {
        
        //创建数据源
        List<Student> listData = createStudents();
        File fileFolder = new File("data/data/cn.lixyz.xmltest/files");
        if (!fileFolder.exists()) {
            fileFolder.mkdir();
            Log.d("TTTT", "文件夹不存在，已经创建");
        }

        FileOutputStream fileOutputStream;
        try {
            fileOutputStream = new FileOutputStream("data/data/cn.lixyz.xmltest/files/studentForPull.xml");
            
            XmlSerializer xmlSerializer = Xml.newSerializer();
            xmlSerializer.setOutput(fileOutputStream, "UTF-8");

            xmlSerializer.startTag(null, "students");
            
            for (Student student : listData) {
                xmlSerializer.startTag(null, "student");
                xmlSerializer.attribute("", "id", student.getId() + "");

                xmlSerializer.startTag(null, "name");
                xmlSerializer.text(student.getName());
                xmlSerializer.endTag(null, "name");

                xmlSerializer.startTag(null, "age");
                xmlSerializer.text(student.getAge() + "");
                xmlSerializer.endTag(null, "age");
                xmlSerializer.endTag(null, "student");
            }
            xmlSerializer.endTag(null, "students");
            xmlSerializer.endDocument();
        } catch (FileNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IllegalArgumentException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IllegalStateException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }

    // pull读取xml文件
    public void pullReaderXML() {
        List<Student> listData = null;
        Student student = null;

        try {
            FileInputStream fileInputStream = new FileInputStream(
                    new File("data/data/cn.lixyz.xmltest/files/studentForPull.xml"));
            XmlPullParser xmlPullParser = Xml.newPullParser();
            xmlPullParser.setInput(fileInputStream, "UTF-8");

            int event = xmlPullParser.getEventType();

            while (event != xmlPullParser.END_DOCUMENT) {
                switch (event) {
                case XmlPullParser.START_DOCUMENT:
                    listData = new ArrayList<Student>();
                    break;

                case XmlPullParser.START_TAG:
                    if ("student".equals(xmlPullParser.getName())) {
                        student = new Student();
                        int id = Integer.parseInt(xmlPullParser.getAttributeValue(0));
                        student.setId(id);
                    } else if ("name".equals(xmlPullParser.getName())) {
                        String name = xmlPullParser.nextText();
                        student.setName(name);
                    } else if ("age".equals(xmlPullParser.getName())) {
                        int age = Integer.parseInt(xmlPullParser.nextText());
                        student.setAge(age);
                    }
                    break;
                case XmlPullParser.END_TAG:
                    if ("student".equals(xmlPullParser.getName())) {
                        listData.add(student);
                    }
                }
                event = xmlPullParser.next();
            }
            for (Student s : listData) {
                Log.d("TTTT", s.getId() + "->" + s.getName() + "->" + s.getAge());
            }
        } catch (XmlPullParserException e) {
            e.printStackTrace();
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (NumberFormatException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    // 模拟生成xml的数据
    private List<Student> createStudents() {
        List<Student> listData = new ArrayList<Student>();
        listData = new ArrayList<Student>();
        Student s1 = new Student();
        s1.setId(11);
        s1.setName("张三");
        s1.setAge(10);
        listData.add(s1);
        Student s2 = new Student();
        s2.setId(22);
        s2.setName("李四");
        s2.setAge(11);
        listData.add(s2);
        Student s3 = new Student();
        s3.setId(33);
        s3.setName("王五");
        s3.setAge(12);
        listData.add(s3);
        Student s4 = new Student();
        s4.setId(44);
        s4.setName("赵六");
        s4.setAge(13);
        listData.add(s4);
        Student s5 = new Student();
        s5.setId(55);
        s5.setName("刘七");
        s5.setAge(14);
        listData.add(s5);
        return listData;
    }
}

Student.java

package cn.lixyz.xmltest.model;

public class Student {

    private int id;
    private String name;
    private int age;

    public int getId() {
        return id;
    }

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

    public String getName() {
        return name;
    }

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

    public int getAge() {
        return age;
    }

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

}