SAX 解析

[功能]

1. SAX 即 org.xml.sax.helpers.DefaultHandler

2. 本例以Google Weather 为例 访问：http://www.google.com/ig/api?weather=chengdu,china

[代码]

1. 定义 WeatherSet 用于保存查询到的数据 以及 这些数据的接口

public class WeatherSet {String humidity;String city;//constructpublic WeatherSet(){}public void setHumidity(String s){humidity = s;}public String getHumidity(){return humidity;}public void setCity(String s){city = s;}public String getCity(){return city;}
}

2. 定制 SAX 并实现以下函数

// 根据一些字符自动回调下面函数* 开始解析
public void startDocument()* 结束解析
public void endDocument()* 遇到元素 <tag >
public void startElement(String namespaceURI, String localName,String qName, Attributes atts)* 遇到元素 </tag >
public void endElement(String namespaceURI, String localName, String qName)* <tag > 与 </tag > 之间
public void characters(char ch[], int start, int length)

 假设我们需要获得以下的信息：

<city data="Chengdu, Sichuan" /><humidity data="湿度： 76%" />

 所以WeatherHandlerr如下：

public class WeatherHandler extends org.xml.sax.helpers.DefaultHandler {WeatherSet weather;private boolean iteration = false;public WeatherHandler(WeatherSet set){weather = set;}@Override  // called when Handler beginpublic void startDocument() throws SAXException {}public void endDocument() throws SAXException {}public void startElement(String namespaceURI, String localName,String qName, Attributes atts) throws SAXException {if (localName.equals("forecast_information")) {iteration = true;}else if(localName.equals("city")) {if(iteration == true){String attrValue = atts.getValue("data");weather.setCity(attrValue);iteration = false;}}if (localName.equals("current_conditions")) {iteration = true;}else if(localName.equals("humidity")) {if(iteration == true){String attrValue = atts.getValue("data");weather.setHumidity(attrValue);iteration = false;}}}public void endElement(String namespaceURI, String localName, String qName)throws SAXException {}public void characters(char ch[], int start, int length) {}}

3. 如何使用 WeatherHandler

* 定义目标URL

String city = "chengdu,china";String queryString = "http://www.google.com/ig/api?weather="+ city;URI uri = new URL(queryString.replace(" ", "%20"));

* 定义 XMLReader 并指定所需的 org.xml.sax.helpers.DefaultHandler

SAXParserFactory spf = SAXParserFactory.newInstance();SAXParser sp = spf.newSAXParser();XMLReader xr = sp.getXMLReader();WeatherHandler handler = new WeatherHandler(weather);xr.setContentHandler(handler);

* 开始解析目标URI

xr.parse(new InputSource(uri.openStream()));

4. 其他问题

* 权限问题：

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

* 运行结果：