【数据存储】DOM操作

准备一：配置权限

 

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

 

 

准备二：判断SD卡

 

if(Environment.getExternalStorageState()
             .equals(Environment.MEDIA_MOUNTED)) {
    File file = new File(Environment.getExternalStorageDirectory()
        + File.separator + DIR + File.separator + FILENAME); 
}

 

<?xml version="1.0" encoding="utf-8"?>
<TableLayout 
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical" 
    android:layout_width="fill_parent"
    android:layout_height="fill_parent">
    <TableRow>
        <TextView 
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"
            android:textSize="20px" 
            android:text="姓名：" />
        <EditText
            android:id="@+id/name" 
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"
            android:text="李兴华" />
    </TableRow>
    <TableRow>
        <TextView 
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"
            android:textSize="20px" 
            android:text="邮箱：" />
        <EditText
            android:id="@+id/email" 
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"
            android:text="mldnqa@163.com" />
    </TableRow>
    <TableRow>
        <Button
            android:id="@+id/but" 
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"
            android:text="保存" />
    </TableRow>
</TableLayout>

package org.lxh.demo;

import java.io.File;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;
import javax.xml.transform.OutputKeys;
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerConfigurationException;
import javax.xml.transform.TransformerException;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.dom.DOMSource;
import javax.xml.transform.stream.StreamResult;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import android.app.Activity;
import android.os.Bundle;
import android.os.Environment;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;

public class MyDOMDemo extends Activity {
    private EditText name = null ;
    private EditText email = null ;
    private Button but = null ;
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        super.setContentView(R.layout.main);
        this.name = (EditText) super.findViewById(R.id.name) ;
        this.email = (EditText) super.findViewById(R.id.email) ;
        this.but = (Button) super.findViewById(R.id.but) ;
        this.but.setOnClickListener(new OnClickListenerImpl()) ;
    }
    private class OnClickListenerImpl implements OnClickListener{
        @Override
        public void onClick(View v) {
            if (!Environment.getExternalStorageState().equals(
                    Environment.MEDIA_MOUNTED)) {    // 不存在不操作
                return; // 返回到程序的被调用处
            }
            File file = 
              new File(Environment.getExternalStorageDirectory()
                    + File.separator + "mldndata" + File.separator
                    + "member.xml");    // 要输出文件的路径
            // 父路径不存在
            if (!file.getParentFile().exists()) { 
                // 创建父文件夹
                file.getParentFile().mkdirs() ;    
            }
            // 1、建立DocumentBuilderFactory，以用于取得DocumentBuilder
            DocumentBuilderFactory factory =
                    DocumentBuilderFactory.newInstance() ;
            // 2、通过DocumentBuilderFactory取得DocumentBuilder
            DocumentBuilder builder = null ;
            try {
                builder = factory.newDocumentBuilder() ;
            } catch (ParserConfigurationException e) {
                e.printStackTrace();
            }
    // 3、定义Document接口对象，通过DocumentBuilder类进行DOM树的转换操作
            Document doc = null ;
            // 创建一个新的文档
            doc = builder.newDocument() ;    
            // 4、建立各个操作节点
            Element addresslist = doc.createElement("addresslist") ;
            Element linkman = doc.createElement("linkman") ;
            Element name = doc.createElement("name") ;
            Element email = doc.createElement("email") ;
            // 5、设置节点的文本内容，即为每一个节点添加文本点
            name.appendChild(doc.createTextNode(MyDOMDemo.this
                  .name.getText().toString()));
            email.appendChild(doc.createTextNode(MyDOMDemo.this
                  .email.getText().toString()));
            // 6、设置节点关系
            linkman.appendChild(name) ;
            linkman.appendChild(email) ;
            addresslist.appendChild(linkman) ;
            doc.appendChild(addresslist) ;
            // 7、输出文档到文件中
            TransformerFactory tf =
                     TransformerFactory.newInstance() ;
            Transformer t = null ;
            try {
                t = tf.newTransformer() ;
            } catch (TransformerConfigurationException e) {
                e.printStackTrace();
            }
            // 设置编码
            t.setOutputProperty(OutputKeys.ENCODING, "GBK") ;
            // 输出文档
            DOMSource source = new DOMSource(doc);
            // 指定输出位置
            StreamResult result = new StreamResult(file) ;
            try {
                // 输出
                t.transform(source, result) ;
            } catch (TransformerException e) {
                e.printStackTrace();
            }
        }
    }
}

以下是通过DOM读取XML

package org.lxh.demo;

import java.io.File;
import java.io.IOException;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.NodeList;
import org.xml.sax.SAXException;
import android.app.Activity;
import android.os.Bundle;
import android.os.Environment;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.TextView;

public class MyDOMDemo extends Activity {
    private TextView name = null;
    private TextView email = null;
    private Button but = null;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        super.setContentView(R.layout.main);
        this.name = (TextView) super.findViewById(R.id.name);
        this.email = (TextView) super.findViewById(R.id.email);
        this.but = (Button) super.findViewById(R.id.but);
        this.but.setOnClickListener(new OnClickListenerImpl());
    }
    private class OnClickListenerImpl implements OnClickListener {
        @Override
        public void onClick(View v) {
            if (!Environment.getExternalStorageState().equals(
                    Environment.MEDIA_MOUNTED)) { // 不存在不操作
                return; // 返回到程序的被调用处
            }
            File file = new
                  File(Environment.getExternalStorageDirectory()
                    + File.separator + "mldndata" + File.separator
                    + "member.xml"); // 要输出文件的路径
            if (!file.exists()) { // 文件不存在
                return;
            }
            // 1、建立DocumentBuilderFactory，以用于取得DocumentBuilder
            DocumentBuilderFactory factory = DocumentBuilderFactory
                    .newInstance();
            // 2、通过DocumentBuilderFactory取得DocumentBuilder
            DocumentBuilder builder = null;
            try {
                builder = factory.newDocumentBuilder();
            } catch (ParserConfigurationException e) {
                e.printStackTrace();
            }
    // 3、定义Document接口对象，通过DocumentBuilder类进行DOM树的转换操作
            Document doc = null;
            try {
                // 通过文件转化文档
                doc = builder.parse(file); 
            } catch (SAXException e1) {
                e1.printStackTrace();
            } catch (IOException e1) {
                e1.printStackTrace();
            }
            // 4、查找linkman节点
            NodeList nl = doc.getElementsByTagName("linkman");
            // 5、输出NodeList中第一个子节点中文本节点的内容
            for (int x = 0; x < nl.getLength(); x++) {
                // 取得元素
                Element e = (Element) nl.item(x); 
                // 设置文本
                MyDOMDemo.this.name.setText(e.getElementsByTagName
                  ("name").item(0).getFirstChild().getNodeValue());
                MyDOMDemo.this.email.setText(e.getElementsByTagName
                  ("email").item(0).getFirstChild().getNodeValue());
            }
        }
    }
}

本程序采用DOM解析方式从member.xml文件中将姓名和邮箱的信息读取出来，并且将内容设置到文本显示组件上显示。