SAX 解析

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;
	
	//construct
	public 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 begin
     public 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：