Android SDK支持采用SAX技術讀取XML,SAX采用順序讀取的方式來處理XML文檔。這就要求在每讀取XML文檔的某個節點時會觸發相應的事件來處理這個節點。下面基于一個實例講述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="語文"
book:id="001"
book:price="45"
book:publisher="A">12</book>
<book
book:name="數學"
book:id="002"
book:price="50"
book:publisher="B">10</book>
<book
book:name="英語"
book:id="003"
book:price="55"
book:publisher="C">21</book>
</books>
~~~
XMLTool.java
1.構建一個工廠SAXParserFactory
2.構建并實例化SAXPraser對象
~~~
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);//必須清空緩沖區
}
dataList.add(book);
}
super.endElement(uri, localName, qName);
}
}
~~~
SAX引擎需要處理5個分析點,也可以稱為分析事件。
1.開始分析XML文件。該分析點表示SAX引擎剛剛開始處理XML文件,但是還沒有讀取XML文件中的內容,該分析點對應:
~~~
public void startDocument() throws SAXException
{
// TODO Auto-generated method stub
dataList = new ArrayList<Book>();
}
~~~
在此方法里面可以做一些初始化的工作。
2.開始處理每一個XML元素。也就是遇到<book>這樣的起始標記的時候都會觸發這個分析節點,所對應的事件方法是startElement。在這個節點可以獲得元素的名稱、屬性的相關信息。
~~~
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);
}
~~~
3.處理完每一個XML元素。也就是遇到</book>這樣的結束標記的時候會觸發endElement方法,在該事件中可以獲得當前處理完元素的全部信息。
~~~
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);//必須清空緩沖區
}
dataList.add(book);
}
super.endElement(uri, localName, qName);
}
~~~
4.處理完XML文件。如果SAX引擎將整個XML文件全部掃描完就會出發endDocument方法。這個方法可能不是必須的,但在這個方法中可以完成一些收尾工作,比如說釋放資源等。在該例中我沒有使用。
5.讀取字符分析點。這是一個很重要的分析點。如果沒有這個分析點, 前面的工作相當于白做,雖然掃描了XML文件,但是沒有保存.....而這個分析點所對應的characters事件方法的主要作用就是保存SAX讀取的XML文件內容。具體的說就是<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());
}
}
}
}
~~~
寫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();
}
~~~
Demo:[http://download.csdn.net/detail/tangnengwu/7664719](http://download.csdn.net/detail/tangnengwu/7664719)