标签：android 数据存储 xml stringbuffer 实例
Android SDK只支持采用SAX技术读取XML,SAX采用顺序读取的方式来处理XML文档。这就要求在每读取XML文档的某个节点时会触发相应的事件来处理这个节点。下面基于一个实例讲述SAX的使用：
public class Book
{
private String name;
private String id;
private String price;
private String publisher;
private int count;
.... get,set方法省略
}
XML文件如下：
<?xml version="1.0" encoding="utf-8"?>
<books xmlns:book="http://schemas.android.com/com.example.jsonxmlio">
<book
book:name="语文"
book:id="001"
book:price="45"
book:publisher="A">12</book>
<book
book:name="数学"
book:id="002"
book:price="50"
book:publisher="B">10</book>
<book
book:name="英语"
book:id="003"
book:price="55"
book:publisher="C">21</book>
</books>XMLTool.java
1.构建一个工厂SAXParserFactory
2.构建并实例化SAXPraser对象
public class XMLTool {
private static SAXParser getSAXParser() throws ParserConfigurationException, SAXException
{
SAXParserFactory parserFactory = SAXParserFactory.newInstance();
return parserFactory.newSAXParser();
}
public static DefaultHandler parse(InputStream inStream,DefaultHandler handler){
if(inStream!=null){
try {
SAXParser parser = getSAXParser();
parser.parse(inStream, handler);
return handler;
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}finally{
if(inStream!=null){
try {
inStream.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
}
return null;
}
}
BookXMLParser.java
public class BookXMLParser extends DefaultHandler
{
private ArrayList<Book> dataList;
private Book book;
private StringBuffer stringBuffer = new StringBuffer();
//private StringBuffer buffer=new StringBuffer();
public ArrayList<Book> getData()
{
return dataList;
}
public void startDocument() throws SAXException
{
// TODO Auto-generated method stub
dataList = new ArrayList<Book>();
}
public void startElement(String uri, String localName, String qName,
Attributes attributes) throws SAXException
{
// TODO Auto-generated method stub
if(qName.equals("book"))
{
book = new Book();
book.setName(attributes.getValue("book:name"));
book.setId(attributes.getValue("book:id"));
book.setPrice(attributes.getValue("book:price"));
book.setPublisher(attributes.getValue("book:publisher"));
}
super.startElement(uri, localName, qName, attributes);
}
@Override
public void characters(char[] ch, int start, int length)
throws SAXException {
// TODO Auto-generated method stub
stringBuffer.append(ch,start,length);
super.characters(ch, start, length);
}
@Override
public void endElement(String uri, String localName, String qName)
throws SAXException {
// TODO Auto-generated method stub
if(qName.equals("book"))
{
if(stringBuffer.toString()!=null && !stringBuffer.toString().equals(""))
{
book.setCount(Integer.parseInt(stringBuffer.toString().trim()));
stringBuffer.setLength(0);//必须清空缓冲区
}
dataList.add(book);
}
super.endElement(uri, localName, qName);
}
}1.开始分析XML文件。该分析点表示SAX引擎刚刚开始处理XML文件，但是还没有读取XML文件中的内容，该分析点对应：
public void startDocument() throws SAXException
{
// TODO Auto-generated method stub
dataList = new ArrayList<Book>();
}2.开始处理每一个XML元素。也就是遇到<book>这样的起始标记的时候都会触发这个分析节点，所对应的事件方法是startElement。在这个节点可以获得元素的名称、属性的相关信息。
public void startElement(String uri, String localName, String qName,
Attributes attributes) throws SAXException
{
// TODO Auto-generated method stub
if(qName.equals("book"))
{
book = new Book();
book.setName(attributes.getValue("book:name"));
book.setId(attributes.getValue("book:id"));
book.setPrice(attributes.getValue("book:price"));
book.setPublisher(attributes.getValue("book:publisher"));
}
super.startElement(uri, localName, qName, attributes);
} public void endElement(String uri, String localName, String qName)
throws SAXException {
// TODO Auto-generated method stub
if(qName.equals("book"))
{
if(stringBuffer.toString()!=null && !stringBuffer.toString().equals(""))
{
book.setCount(Integer.parseInt(stringBuffer.toString().trim()));
stringBuffer.setLength(0);//必须清空缓冲区
}
dataList.add(book);
}
super.endElement(uri, localName, qName);
}5.读取字符分析点。这是一个很重要的分析点。如果没有这个分析点， 前面的工作相当于白做，虽然扫描了XML文件，但是没有保存.....而这个分析点所对应的characters事件方法的主要作用就是保存SAX读取的XML文件内容。具体的说就是<book ... ...>12</book>中的“12”
public void characters(char[] ch, int start, int length)
throws SAXException {
// TODO Auto-generated method stub
stringBuffer.append(ch,start,length);
super.characters(ch, start, length);
}使用SAX解析XML:
public class MainActivity extends Activity
{
private List<Book> books;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
InputStream inStream = getResources().openRawResource(R.raw.books);
BookXMLParser parser = new BookXMLParser();
books = ((BookXMLParser)XMLTool.parse(inStream, parser)).getData();
if(books!=null && books.size()>0)
{
for(int i = 0;i<books.size();i++)
{
Log.d("AAA", books.get(i).toString());
}
}
}
}
写XML文件
public static void WriteXML(List<Book> books, OutputStream out) throws Exception
{
XmlSerializer serializer = Xml.newSerializer();
serializer.setOutput(out, "UTF-8");
serializer.startDocument("UTF-8", true);
serializer.startTag(null, "books");
for (Book book : books)
{
serializer.startTag(null, "book");
serializer.attribute(null, "book:name", book.getName());
serializer.attribute(null, "book:id",book.getId());
serializer.attribute(null, "book:price", book.getPrice());
serializer.attribute(null, "book:publisher",book.getPublisher());
serializer.text(String.valueOf(book.getCount()));
serializer.endTag(null, "book");
}
serializer.endTag(null, "books");
serializer.endDocument();
out.flush();
out.close();
}标签：android 数据存储 xml stringbuffer 实例
原文地址：http://blog.csdn.net/tangnengwu/article/details/38043793
