Java 从RSS源获取前5项-Android

我目前正在开发一个RSS提要阅读应用程序，该应用程序将访问多个RSS提要并返回xml，然后对其进行解析

我想知道的是，是否有办法只带回RSS提要中的前5项；这样就减少了恢复数据所需的时间

任何指导都将不胜感激，谢谢

这是我正在使用的代码：

如何调用XMLParser：

XMLParser parser = new XMLParser();
String xml = parser.getXmlFromUrl(URL[f]); // getting XML
Document doc = parser.getDomElement(xml); // getting DOM element

package com.example.directrssread;

import java.io.IOException;
import java.io.StringReader;
import java.io.UnsupportedEncodingException;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;

import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.impl.client.DefaultHttpClient;
import org.apache.http.util.EntityUtils;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
import org.xml.sax.InputSource;
import org.xml.sax.SAXException;

import android.util.Log;

public class XMLParser {

    // constructor
    public XMLParser() {

    }

    /**
     * Getting XML from URL making HTTP request
     * @param url string
     * */
    public String getXmlFromUrl(String url) {
        String xml = null;

        try {
            // defaultHttpClient
            DefaultHttpClient httpClient = new DefaultHttpClient();
            //HttpPost httpPost = new HttpPost(url);
            HttpGet httpPost = new HttpGet(url);

            HttpResponse httpResponse = httpClient.execute(httpPost);
            HttpEntity httpEntity = httpResponse.getEntity();
            xml = EntityUtils.toString(httpEntity);

        } catch (UnsupportedEncodingException e) {
            e.printStackTrace();
        } catch (ClientProtocolException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
        // return XML
        return xml;
    }

    /**
     * Getting XML DOM element
     * @param XML string
     * */
    public Document getDomElement(String xml){
        Document doc = null;
        DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
        try {

            DocumentBuilder db = dbf.newDocumentBuilder();
            dbf.setCoalescing(true);   
            if (db!=null)
            {
            InputSource is = new InputSource();
                is.setCharacterStream(new StringReader(xml));
                doc = db.parse(is); 
            }

            } catch (ParserConfigurationException e) {
                Log.e("Error: ", e.getMessage());
                return null;
            } catch (SAXException e) {
                Log.e("Error: ", e.getMessage());
                return null;
            } catch (IOException e) {
                Log.e("Error: ", e.getMessage());
                return null;
            }

            return doc;
    }

    /** Getting node value
      * @param elem element
      */
    public final String getElementValue2( Node elem ) {  
        Node child;  
        if( elem != null){  
            if (elem.hasChildNodes()){  
                for( child = elem.getFirstChild(); child != null; child = child.getNextSibling() ){  
                    //if( child.getNodeType() == Node.TEXT_NODE  ){  
                     if( child.getNodeType() == Node.TEXT_NODE || child.getNodeType() == Node.CDATA_SECTION_NODE  ){       
                        return child.getNodeValue();  
                    }  
                }  
            }  
        }  
        return "";  
        //return elem.getTextContent();  
    } 

     /**
      * Getting node value
      * @param Element node
      * @param key string
      * */
     public String getValue(Element item, String str) {     
            NodeList n = item.getElementsByTagName(str);        
            return this.getElementValue2(n.item(0));
        }


}

XMLParser：

XMLParser parser = new XMLParser();
String xml = parser.getXmlFromUrl(URL[f]); // getting XML
Document doc = parser.getDomElement(xml); // getting DOM element

package com.example.directrssread;

import java.io.IOException;
import java.io.StringReader;
import java.io.UnsupportedEncodingException;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;

import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.impl.client.DefaultHttpClient;
import org.apache.http.util.EntityUtils;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
import org.xml.sax.InputSource;
import org.xml.sax.SAXException;

import android.util.Log;

public class XMLParser {

    // constructor
    public XMLParser() {

    }

    /**
     * Getting XML from URL making HTTP request
     * @param url string
     * */
    public String getXmlFromUrl(String url) {
        String xml = null;

        try {
            // defaultHttpClient
            DefaultHttpClient httpClient = new DefaultHttpClient();
            //HttpPost httpPost = new HttpPost(url);
            HttpGet httpPost = new HttpGet(url);

            HttpResponse httpResponse = httpClient.execute(httpPost);
            HttpEntity httpEntity = httpResponse.getEntity();
            xml = EntityUtils.toString(httpEntity);

        } catch (UnsupportedEncodingException e) {
            e.printStackTrace();
        } catch (ClientProtocolException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
        // return XML
        return xml;
    }

    /**
     * Getting XML DOM element
     * @param XML string
     * */
    public Document getDomElement(String xml){
        Document doc = null;
        DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
        try {

            DocumentBuilder db = dbf.newDocumentBuilder();
            dbf.setCoalescing(true);   
            if (db!=null)
            {
            InputSource is = new InputSource();
                is.setCharacterStream(new StringReader(xml));
                doc = db.parse(is); 
            }

            } catch (ParserConfigurationException e) {
                Log.e("Error: ", e.getMessage());
                return null;
            } catch (SAXException e) {
                Log.e("Error: ", e.getMessage());
                return null;
            } catch (IOException e) {
                Log.e("Error: ", e.getMessage());
                return null;
            }

            return doc;
    }

    /** Getting node value
      * @param elem element
      */
    public final String getElementValue2( Node elem ) {  
        Node child;  
        if( elem != null){  
            if (elem.hasChildNodes()){  
                for( child = elem.getFirstChild(); child != null; child = child.getNextSibling() ){  
                    //if( child.getNodeType() == Node.TEXT_NODE  ){  
                     if( child.getNodeType() == Node.TEXT_NODE || child.getNodeType() == Node.CDATA_SECTION_NODE  ){       
                        return child.getNodeValue();  
                    }  
                }  
            }  
        }  
        return "";  
        //return elem.getTextContent();  
    } 

     /**
      * Getting node value
      * @param Element node
      * @param key string
      * */
     public String getValue(Element item, String str) {     
            NodeList n = item.getElementsByTagName(str);        
            return this.getElementValue2(n.item(0));
        }


}

---

使用顺序解析器sax，然后由您的实现来计算读取的项目，停止读取过程并关闭输入流。Dom对于移动设备来说可能有点笨拙。

您可以尝试使用线性解析器，如XmlPullParser，保留一个计数器，并在需要时中断。然而，我认为URL连接需要很长时间。在我的XML解析器中，我注意到检索15个项目的简单提要大约需要1.5秒，而解析它们只需要100毫秒。