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

2023-01-10 11:50:21

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;

    }

}

　　

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