公司客户需求中有一个内置几个电话号码,看了一下以前工程师的代码,是采用xml文件的形式来配置几个号码,然后对应的把xml文件解析,再将这些号码插入到contacts的db数据库中。正好借这个机会,学习一下xml文件的解析。
XML文件作为承载数据的一个重要角色,非常非常用户来配置和客置化,所以读写XML文件是Android开发中一项重要的技能。
在Android中,常见的XML解析器分别为SAX解析器、DOM解析器和PULL解析器:
SAX(Simple API for XML)解析器是一种基于事件的解析器,它的核心是事件处理模式,主要是围绕着事件源以及事件处理器来工作的。当事件源产生事件后,调用事件处理器相应的处理方法,一个事件就可以得到处理。在事件源调用事件处理器中特定方法的时候,还要传递给事件处理器相应事件的状态信息,这样事件处理器才能够根据提供的事件信息来决定自己的行为。
SAX解析器的优点是解析速度快,占用内存少。非常适合在Android移动设备中使用。
DOM是基于树形结构的的节点或信息片段的集合,允许开发人员使用DOM API遍历XML树、检索所需数据。
分析该结构通常需要加载整个文档和构造树形结构,然后才可以检索和更新节点信息。由于DOM在内存中以树形结构存放,因此检索和更新效率会更高。但是对于特别大的文档,解析和加载整个文档将会很耗资源。
PULL解析器的运行方式和SAX类似,都是基于事件的模式。
不同的是,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,而不像SAX那样由处理器触发一种事件的方法,执行我们的代码。
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。
我们的项目代码结构:
先在assets目录中放置一个XML文档book.xml,内容如下:
<?xml version="1.0" encoding="utf-8"?>
<books>
<book>
<id>1001</id>
<name>Thinking In Java</name>
<price>80.00</price>
</book>
<book>
<id>1002</id>
<name>Core Java</name>
<price>90.00</price>
</book>
<book>
<id>1003</id>
<name>Hello, Andriod</name>
<price>100.00</price>
</book>
</books>
再定义一个Book.java类:
package com.example.android.xml.util;
public class Book {
private int id;
private String name;
private float prince;
public Book(int id, String name, float prince) {
this.id = id;
this.name = name;
this.prince = prince;
}
public Book() {
}
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 float getPrince() {
return prince;
}
public void setPrince(float prince) {
this.prince = prince;
}
@Override
public String toString() {
return "Book{" +
"id=" + id +
", name='" + name + '\'' +
", prince=" + prince +
'}';
}
}
再定义一个Util 类:
public class Util {
public static final String ITEMS = "books";
public static final String ITEM = "book";
public static final String KEY_1 = "id";
public static final String KEY_2 = "name";
public static final String KEY_3 = "price";
}
最后,我们还要把这个xml文件读取的数据生成一个新的XML文档,文档路径/data/data//files/books.xml,当然查看这个路径需要userdebug或debug版本。
<?xml version="1.0" encoding="UTF-8"?>
<books>
<book id="1001">
<name>Thinking In Java</name>
<price>80.0</price>
</book>
<book id="1002">
<name>Core Java</name>
<price>90.0</price>
</book>
<book id="1003">
<name>Hello, Andriod</name>
<price>100.0</price>
</book>
</books>
然后,我们定义一个IParse.java文件,这是一个接口,声明了一个parse方法:
import java.io.InputStream;
import java.util.List;
public interface IParse {
public List<Book> parse(InputStream is) throws Exception;
}
然后分别实现此parse方法:
SAXParse.java 实现接口IParse,用SAX的方法解析xml文件:
import android.util.Log;
import org.xml.sax.Attributes;
import org.xml.sax.SAXException;
import org.xml.sax.helpers.DefaultHandler;
import java.io.InputStream;
import java.util.ArrayList;
import java.util.List;
import javax.xml.parsers.SAXParser;
import javax.xml.parsers.SAXParserFactory;
public class SAXParse implements IParse {
public static final String TAG = "SAXParse";
@Override
public List<Book> parse(InputStream is) throws Exception {
SAXParserFactory factory = SAXParserFactory.newInstance(); //取得SAXParserFactory实例
SAXParser parser = factory.newSAXParser(); //从factory获取SAXParser实例
MyHandler handler = new MyHandler(); //实例化自定义Handler
parser.parse(is, handler); //根据自定义Handler规则解析输入流
return handler.getBooks();
}
//需要重写DefaultHandler的方法
private class MyHandler extends DefaultHandler {
private List<Book> books;
private Book book;
private StringBuilder builder;
//返回解析后得到的Book对象集合
public List<Book> getBooks() {
return books;
}
@Override
public void startDocument() throws SAXException {
super.startDocument();
Log.i(TAG, "--------MyHandler----startDocument---------");
books = new ArrayList<Book>();
builder = new StringBuilder();
}
@Override
public void startElement(String uri, String localName, String qName, Attributes attributes)
throws SAXException {
super.startElement(uri, localName, qName, attributes);
Log.i(TAG, "--------MyHandler----startElement---------");
Log.i(TAG, "--------MyHandler----startElement---------localName:"+localName);
if (localName.equals(Util.ITEM)) {
book = new Book();
}
builder.setLength(0); //将字符长度设置为0 以便重新开始读取元素内的字符节点
}
@Override
public void characters(char[] ch, int start, int length) throws SAXException {
super.characters(ch, start, length);
Log.i(TAG, "--------MyHandler----characters---------");
Log.i(TAG, "--------MyHandler----characters---------builder:"+builder);
builder.append(ch, start, length); //将读取的字符数组追加到builder中
}
@Override
public void endElement(String uri, String localName, String qName) throws SAXException {
super.endElement(uri, localName, qName);
Log.i(TAG, "--------MyHandler----endElement---------");
Log.i(TAG, "--------MyHandler----endElement---------localName:"+localName);
Log.i(TAG, "--------MyHandler----endElement---------builder:"+builder);
if (localName.equals(Util.KEY_1)) {
book.setId(Integer.parseInt(builder.toString()));
} else if (localName.equals(Util.KEY_2)) {
book.setName(builder.toString());
} else if (localName.equals(Util.KEY_3)) {
book.setPrince(Float.parseFloat(builder.toString()));
} else if (localName.equals(Util.ITEM)) {
books.add(book);
}
}
}
}
DOMParse.java 实现接口IParse,用DOM的方法解析xml文件:
import android.util.Log;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
import java.io.InputStream;
import java.util.ArrayList;
import java.util.List;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
public class DOMParse implements IParse {
public static final String TAG = "DOMParse";
@Override
public List<Book> parse(InputStream is) throws Exception{
List<Book> books = new ArrayList<Book>();
DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
DocumentBuilder builder = factory.newDocumentBuilder();
Document doc = builder.parse(is);
Element rootElement = doc.getDocumentElement();
NodeList items = rootElement.getElementsByTagName(Util.ITEM);
for (int i = 0; i < items.getLength(); i++) {
Book book = new Book();
Node item = items.item(i);
NodeList properties = item.getChildNodes();
for (int j = 0; j < properties.getLength(); j++) {
Node property = properties.item(j);
String nodeName = property.getNodeName();
Log.i(TAG, "nodeName:" + nodeName);
if (nodeName.equals(Util.KEY_1)) {
Log.i(TAG, "property.getFirstChild().getNodeValue():" + property.getFirstChild().getNodeValue());
book.setId(Integer.parseInt(property.getFirstChild().getNodeValue()));
} else if (nodeName.equals(Util.KEY_2)) {
Log.i(TAG, "property.getFirstChild().getNodeValue():" + property.getFirstChild().getNodeValue());
book.setName(property.getFirstChild().getNodeValue());
} else if (nodeName.equals(Util.KEY_3)) {
Log.i(TAG, "property.getFirstChild().getNodeValue():" + property.getFirstChild().getNodeValue());
book.setPrince(Float.parseFloat(property.getFirstChild().getNodeValue()));
}
}
books.add(book);
}
return books;
}
}
PULLParse .java 实现接口IParse,用PULL的方法解析xml文件:
import android.util.Log;
import android.util.Xml;
import org.xmlpull.v1.XmlPullParser;
import java.io.InputStream;
import java.util.ArrayList;
import java.util.List;
public class PULLParse implements IParse {
public static final String TAG = "PULLParse";
@Override
public List<Book> parse(InputStream is) throws Exception {
List<Book> books = null;
Book book = null;
XmlPullParser parser = Xml.newPullParser();
parser.setInput(is, "UTF-8");
int eventType = parser.getEventType();
Log.i(TAG,"eventType:"+eventType);
while (eventType != XmlPullParser.END_DOCUMENT) {
switch (eventType) {
case XmlPullParser.START_DOCUMENT:
Log.i(TAG,"---------------START_DOCUMENT--------------------");
Log.i(TAG,"XmlPullParser.START_DOCUMENT");
Log.i(TAG,"parser.getName():"+parser.getName());
books = new ArrayList<Book>();
break;
case XmlPullParser.START_TAG:
Log.i(TAG,"-----------------START_TAG------------------");
Log.i(TAG,"XmlPullParser.START_TAG");
Log.i(TAG,"parser.getName():"+parser.getName());
if (parser.getName().equals(Util.ITEM)) {
book = new Book();
} else if (parser.getName().equals(Util.KEY_1)) {
eventType = parser.next();
Log.i(TAG,"parser.getText():"+parser.getText());
book.setId(Integer.parseInt(parser.getText()));
} else if (parser.getName().equals(Util.KEY_2)) {
eventType = parser.next();
Log.i(TAG,"parser.getText():"+parser.getText());
book.setName(parser.getText());
} else if (parser.getName().equals(Util.KEY_3)) {
eventType = parser.next();
Log.i(TAG,"parser.getText():"+parser.getText());
book.setPrince(Float.parseFloat(parser.getText()));
}
break;
case XmlPullParser.END_TAG:
Log.i(TAG,"---------------END_TAG--------------------");
Log.i(TAG,"XmlPullParser.END_TAG:");
Log.i(TAG,"parser.getName():"+parser.getName());
if (parser.getName().equals(Util.ITEM)) {
books.add(book);
book = null;
}
break;
}
eventType = parser.next();
}
return books;
}
}
我们再定义一个序列化接口ISerialize,主要是把从xml文件中读取来的数据重新写到xml文件中:
import java.util.List;
public interface ISerialize {
public String serialize(List<Book> books) throws Exception;
}
对应的,我们再分别用三种方式来实现:
SAXSerialize.java: 用SAX的方式来实现接口ISerialize:
import android.util.Log;
import org.xml.sax.helpers.AttributesImpl;
import java.io.StringWriter;
import java.util.List;
import javax.xml.transform.OutputKeys;
import javax.xml.transform.Result;
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.sax.SAXTransformerFactory;
import javax.xml.transform.sax.TransformerHandler;
import javax.xml.transform.stream.StreamResult;
public class SAXSerialize implements ISerialize {
public static final String TAG = "SAXSerialize";
@Override
public String serialize(List<Book> books) throws Exception {
//取得SAXTransformerFactory实例
SAXTransformerFactory factory = (SAXTransformerFactory) TransformerFactory.newInstance();
//从factory获取TransformerHandler实例
TransformerHandler handler = factory.newTransformerHandler();
//从handler获取Transformer实例
Transformer transformer = handler.getTransformer();
// 设置输出采用的编码方式
transformer.setOutputProperty(OutputKeys.ENCODING, "UTF-8");
// 是否自动添加额外的空白
transformer.setOutputProperty(OutputKeys.INDENT, "yes");
// 是否忽略XML声明
transformer.setOutputProperty(OutputKeys.OMIT_XML_DECLARATION, "no");
StringWriter writer = new StringWriter();
Result result = new StreamResult(writer);
handler.setResult(result);
//代表命名空间的URI 当URI无值时 须置为空字符串
String uri = "";
//命名空间的本地名称(不包含前缀) 当没有进行命名空间处理时 须置为空字符串
String localName = "";
handler.startDocument();
handler.startElement(uri, localName, "books", null);
//负责存放元素的属性信息
AttributesImpl attrs = new AttributesImpl();
char[] ch = null;
for (Book book : books) {
attrs.clear(); //清空属性列表
//添加一个名为id的属性(type影响不大,这里设为string)
attrs.addAttribute(uri, localName, "id", "string", String.valueOf(book.getId()));
//开始一个book元素 关联上面设定的id属性
handler.startElement(uri, localName, "book", attrs);
//开始一个name元素 没有属性
handler.startElement(uri, localName, "name", null);
ch = String.valueOf(book.getName()).toCharArray();
//设置name元素的文本节点
handler.characters(ch, 0, ch.length);
handler.endElement(uri, localName, "name");
//开始一个price元素 没有属性
handler.startElement(uri, localName, "price", null);
ch = String.valueOf(book.getPrince()).toCharArray();
//设置price元素的文本节点
handler.characters(ch, 0, ch.length);
handler.endElement(uri, localName, "price");
handler.endElement(uri, localName, "book");
}
handler.endElement(uri, localName, "books");
handler.endDocument();
Log.i(TAG, "SAXSerialize---serialize--writer.toString():"+writer.toString());
return writer.toString();
}
}
DOMSerialize.java: 用DOM的方式来实现接口ISerialize:
import android.util.Log;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import java.io.StringWriter;
import java.util.List;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.transform.OutputKeys;
import javax.xml.transform.Result;
import javax.xml.transform.Source;
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.dom.DOMSource;
import javax.xml.transform.stream.StreamResult;
public class DOMSerialize implements ISerialize {
public static final String TAG = "DOMSerialize";
@Override
public String serialize(List<Book> books) throws Exception {
DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
DocumentBuilder builder = factory.newDocumentBuilder();
Document doc = builder.newDocument(); //由builder创建新文档
Element rootElement = doc.createElement("books");
for (Book book : books) {
Element bookElement = doc.createElement("book");
bookElement.setAttribute("id", book.getId() + "");
Element nameElement = doc.createElement("name");
nameElement.setTextContent(book.getName());
bookElement.appendChild(nameElement);
Element priceElement = doc.createElement("price");
priceElement.setTextContent(book.getPrince() + "");
bookElement.appendChild(priceElement);
rootElement.appendChild(bookElement);
}
doc.appendChild(rootElement);
TransformerFactory transFactory = TransformerFactory.newInstance();//取得TransformerFactory实例
Transformer transformer = transFactory.newTransformer(); //从transFactory获取Transformer实例
transformer.setOutputProperty(OutputKeys.ENCODING, "UTF-8"); // 设置输出采用的编码方式
transformer.setOutputProperty(OutputKeys.INDENT, "yes"); // 是否自动添加额外的空白
transformer.setOutputProperty(OutputKeys.OMIT_XML_DECLARATION, "no"); // 是否忽略XML声明
StringWriter writer = new StringWriter();
Source source = new DOMSource(doc); //表明文档来源是doc
Result result = new StreamResult(writer);//表明目标结果为writer
transformer.transform(source, result); //开始转换
Log.i(TAG, "SAXSerialize---serialize--writer.toString():" + writer.toString());
return writer.toString();
}
}
PULLSerialize.java: 用PULL的方式来实现接口ISerialize:
import android.util.Log;
import android.util.Xml;
import org.xmlpull.v1.XmlSerializer;
import java.io.StringWriter;
import java.util.List;
public class PULLSerialize implements ISerialize {
public static final String TAG = "PULLSerialize";
@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.getPrince() + "");
serializer.endTag("", "price");
serializer.endTag("", "book");
}
serializer.endTag("", "books");
serializer.endDocument();
Log.i(TAG, "PULLSerialize---serialize--writer.toString():" + writer.toString());
return writer.toString();
}
}
我们界面如下:
其中成局文件如下:
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:app="http://schemas.android.com/apk/res-auto" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" android:paddingBottom="@dimen/activity_vertical_margin" android:paddingLeft="@dimen/activity_horizontal_margin" android:paddingRight="@dimen/activity_horizontal_margin" android:paddingTop="@dimen/activity_vertical_margin" app:layout_behavior="@string/appbar_scrolling_view_behavior" tools:context="com.example.android.xml.MainActivity" tools:showIn="@layout/activity_main">
<Button android:id="@+id/sax_parse" android:layout_width="wrap_content" android:layout_height="wrap_content" android:onClick="clickSaxParse" android:text="sax parse xml"/>
<Button android:id="@+id/sax_serialize" android:layout_toRightOf="@+id/sax_parse" android:layout_width="wrap_content" android:layout_height="wrap_content" android:onClick="clickSaxSerialize" android:text="sax serialize xml"/>
<Button android:id="@+id/dom_parse" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_below="@id/sax_parse" android:onClick="clickDomParse" android:text="dom parse xml"/>
<Button android:id="@+id/dom_serialize" android:layout_toRightOf="@+id/dom_parse" android:layout_alignBottom="@+id/dom_parse" android:layout_width="wrap_content" android:layout_height="wrap_content" android:onClick="clickDomParseSerialize" android:text="Dom serialize xml"/>
<Button android:id="@+id/pull_parse" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_below="@id/dom_parse" android:onClick="clickPullParse" android:text="pull parse xml"/>
<Button android:id="@+id/pull_serialize" android:layout_toRightOf="@+id/pull_parse" android:layout_alignBottom="@+id/pull_parse" android:layout_width="wrap_content" android:layout_height="wrap_content" android:onClick="clickPullParseSerialize" android:text="pull serialize xml"/>
</RelativeLayout>
然后在activity中实现的逻辑如下:
import android.content.Context;
import android.os.Bundle;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.Snackbar;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.util.Log;
import android.view.View;
import com.example.android.xml.util.Book;
import com.example.android.xml.util.DOMParse;
import com.example.android.xml.util.DOMSerialize;
import com.example.android.xml.util.IParse;
import com.example.android.xml.util.ISerialize;
import com.example.android.xml.util.PULLParse;
import com.example.android.xml.util.PULLSerialize;
import com.example.android.xml.util.SAXParse;
import com.example.android.xml.util.SAXSerialize;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.util.List;
public class MainActivity extends AppCompatActivity {
public final static String TAG ="MainActivity";
private IParse parse;
private ISerialize serialize;
private List<Book> books = null;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
fab.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
.setAction("Action", null).show();
}
});
}
public void clickSaxParse(View view){
Log.i(TAG, "clickSaxParse");
try {
InputStream is = getAssets().open("book.xml");
parse = new SAXParse();
// parse = new DomParser();
// parse = new PULLParse();
books = parse.parse(is);
} catch (Exception e) {
e.printStackTrace();
}
printBooks();
}
public void clickDomParse(View view){
Log.i(TAG,"clickDomParse");
try {
InputStream is = getAssets().open("book.xml");
// parse = new SAXParser();
parse = new DOMParse();
// parse = new PULLParse();
books = parse.parse(is);
} catch (Exception e) {
e.printStackTrace();
}
printBooks();
}
public void clickPullParse(View view){
Log.i(TAG,"clickPullParse");
try {
InputStream is = getAssets().open("book.xml");
// parse = new SAXParser();
// parse = new DomParser();
parse = new PULLParse();
books = parse.parse(is);
} catch (Exception e) {
e.printStackTrace();
}
printBooks();
}
public void clickSaxSerialize(View view){
Log.i(TAG, "clickSaxSerialize");
try {
serialize = new SAXSerialize();
//序列化
String xml = serialize.serialize(books);
FileOutputStream fos = openFileOutput("books.xml", Context.MODE_PRIVATE);
fos.write(xml.getBytes("UTF-8"));
} catch (Exception e) {
Log.e(TAG, e.getMessage());
}
}
public void clickDomParseSerialize(View view){
Log.i(TAG,"clickDomParseSerialize");
try {
serialize = new DOMSerialize();
//序列化
String xml = serialize.serialize(books);
FileOutputStream fos = openFileOutput("books.xml", Context.MODE_PRIVATE);
fos.write(xml.getBytes("UTF-8"));
} catch (Exception e) {
Log.e(TAG, e.getMessage());
}
}
public void clickPullParseSerialize(View view){
Log.i(TAG, "clickPullParseSerialize");
try {
serialize = new PULLSerialize();
//序列化
String xml = serialize.serialize(books);
FileOutputStream fos = openFileOutput("books.xml", Context.MODE_PRIVATE);
fos.write(xml.getBytes("UTF-8"));
} catch (Exception e) {
Log.e(TAG, e.getMessage());
}
}
public void printBooks(){
for (Book book : books) {
Log.i(TAG, book.toString());
}
}
}
对于这三种解析器各有优点,因为SAX解析器操作起来太笨重,DOM不适合文档较大,内存较小的场景,唯有PULL轻巧灵活,速度快,占用内存小,使用非常顺手,所以android开发推荐PULL解析器。
(1) Android中解析XML
http://blog.csdn.net/liuhe688/article/details/6415593
(2)【Android】实现XML解析的几种技术
http://www.cnblogs.com/weixing/archive/2013/08/07/3243366.html