Android利用Document实现xml读取和写入操作

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 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"
  android:orientation="vertical"
  tools:context="com.oak.d3_xml.MainActivity">
 
  <TextView
    android:id="@+id/tv"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="Hello World!" />
  <Button
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="生成"
    android:id="@+id/bt_create"/>
  <Button
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="读取"
    android:id="@+id/bt_read"/>
</LinearLayout>

package com.oak.d3_xml;
 
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import android.widget.Toast;
 
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.NodeList;
import org.xml.sax.SAXException;
 
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;
 
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;
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;
 
 
public class MainActivity extends AppCompatActivity {
  private TextView textView;//用于展示读取xml的内容
  private Button bt_create;//用于创建xml文件
  private Button bt_read;//用于读取xml文件
  private File file;//xml文件路径
  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    file = new File(getFilesDir(),"languages.xml");//获取到xml文件
    textView = (TextView) findViewById(R.id.tv);//拿到textView控件
    bt_create = (Button) findViewById(R.id.bt_create);//拿到创建按钮
    bt_read = (Button) findViewById(R.id.bt_read);//拿到读取按钮
 
    bt_create.setOnClickListener(new View.OnClickListener() {
      @Override
      public void onClick(View view) {
        //这里利用的是dom对xml进行操作的
        //实例化一个DocmentBuilderFactory，调用其静态方法获取
        DocumentBuilderFactory builderFactory = DocumentBuilderFactory.newInstance();
        try {
          //实例化一个DocumentBuilder
          DocumentBuilder builder = builderFactory.newDocumentBuilder();
          //实例化一个xml文件
          Document newxml = builder.newDocument();
          //创建一个根标签
          Element languages = newxml.createElement("languages");
          //为其设置属性
          languages.setAttribute("cat","it");
          //for循坏3次，分别创建出三个标签，每个标签都包含内容
          for (int i=0;i<3;i++){
            //创建languages的子标签lan
            Element lan = newxml.createElement("lan");
            //设置属性
            lan.setAttribute("id",i+"");
            //创建lan的子标签
            Element name = newxml.createElement("name");
            //设置内容
            name.setTextContent("Java"+i);
            //创建lan的子标签
            Element ide = newxml.createElement("ide");
            //设置内容
            ide.setTextContent("Eclipse"+i);
            //将name和ide分别加入lan这个标签中
            lan.appendChild(name);
            lan.appendChild(ide);
            //将lan将入languages标签中
            languages.appendChild(lan);
          }
          //将languages加入到xml文件中
          newxml.appendChild(languages);
          //实例化Transformer工厂
          TransformerFactory transformerFactory = TransformerFactory.newInstance();
          //获取到Transformer
          Transformer transformer = transformerFactory.newTransformer();
          //设置输出格式
          transformer.setOutputProperty("encoding","UTF-8");
          //设置输出流
          OutputStream os = new FileOutputStream(file);
          //将文件写出
          transformer.transform(new DOMSource(newxml),new StreamResult(os));
          Toast.makeText(getApplicationContext(),"生成成功",Toast.LENGTH_SHORT).show();
        } catch (ParserConfigurationException e) {
          e.printStackTrace();
        } catch (TransformerConfigurationException e) {
          e.printStackTrace();
        } catch (FileNotFoundException e) {
          e.printStackTrace();
        } catch (TransformerException e) {
          e.printStackTrace();
        }
      }
    });
    bt_read.setOnClickListener(new View.OnClickListener() {
      @Override
      public void onClick(View view) {
        //获取到DocumentBuilder的工厂实例化
        DocumentBuilderFactory builderFactory = DocumentBuilderFactory.newInstance();
        try {
          //拿到DocumentBuilder
          DocumentBuilder builder = builderFactory.newDocumentBuilder();
          //解析xml文件
          Document xml = builder.parse(file);
          //获取其根标签
          Element languages = xml.getDocumentElement();
          //根据子标签进行查找，返回的是一个list集合
          NodeList list = languages.getElementsByTagName("lan");
          textView.setText("");//将textView中的内容置空
          for (int i=0; i<list.getLength(); i++){
            //获取到子标签lan
            Element lan = (Element) list.item(i);
            //获取到他的属性
            String id = lan.getAttribute("id");
            //获取到他的子标签name的内容
            String name = lan.getElementsByTagName("name").item(0).getTextContent();
            //获取到他的子标签ide的内容
            String ide = lan.getElementsByTagName("ide").item(0).getTextContent();
            //显示到textView中
            textView.append(id+"\n"+name+"\n"+ide+"\n");
          }
        } catch (ParserConfigurationException e) {
          e.printStackTrace();
        } catch (SAXException e) {
          e.printStackTrace();
        } catch (IOException e) {
          e.printStackTrace();
        }
 
      }
    });
  }
}