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我正在尝试制作一个解析 RSS 提要的应用程序。我运行我的应用程序，但是虽然源链接 ( http://api.androidhive.info/music/music.xml ) 非常快，但数据的获取速度非常慢。

我需要我的应用程序快速响应。

我的应用程序代码：

package com.sta.map;

import java.util.ArrayList;
import java.util.HashMap;

import org.w3c.dom.Document;
import org.w3c.dom.NodeList;
import org.w3c.dom.Element;


import android.app.Activity;
import android.app.ProgressDialog;
import android.os.AsyncTask;
import android.os.Bundle;
import android.widget.ListView;
import android.widget.TextView;

public class POSTS extends Activity {
    static final String KEY_ARTIST = "artist";
    static final String KEY_THUMB_URL = "thumb_url";

    ListView list;
    WbAdapter adapter;

    static String URL = "http://api.androidhive.info/music/music.xml";

    ProgressDialog pDialog;

    ArrayList<HashMap<String, String>> songsList = new ArrayList<HashMap<String, String>>();
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.posts);

        new ParseXMLTask().execute();
    }

    class ParseXMLTask extends AsyncTask<String, String, String> {
        protected void onPreExecute() {
            // Showing progress dialog before sending http request
            pDialog = new ProgressDialog(POSTS.this);
            pDialog.setMessage("Please wait..");
            pDialog.setIndeterminate(true);
            pDialog.setCancelable(false);
            pDialog.show();
        }
        @Override
        protected String doInBackground(String... unused) {
           XMLParser parser = new XMLParser();
           String xml = parser.getXmlFromUrl(url); // getting XML from URL
            return xml;
        }

        @Override
        protected void onPostExecute(String result) {
            pDialog.dismiss();
            XMLParser parser = new XMLParser();
            Document doc = parser.getDomElement(result); // getting DOM element

            NodeList nl = doc.getElementsByTagName("song");
            // looping through all song nodes <song>
            for (int i = 0; i < nl.getLength(); i++) {
                // creating new HashMap
                HashMap<String, String> map = new HashMap<String, String>();
                Element e = (Element) nl.item(i);
                // adding each child node to HashMap key => value
                map.put(KEY_ARTIST, parser.getValue(e, KEY_ARTIST));
                map.put(KEY_THUMB_URL, parser.getValue(e, KEY_THUMB_URL));

                // adding HashList to ArrayList
                songsList.add(map);
            }

            list=(ListView)findViewById(R.id.list);
            adapter= new WbAdapter(POSTS.this, songsList);        
            list.setAdapter(adapter);
        }   
    }
}

XMLParser班级 ：

package com.sta.map;

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.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);

            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();

            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 getElementValue( 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  ){
                         return child.getNodeValue();
                     }
                 }
             }
         }
         return "";
     }

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

编辑1：在清单中我发现了这段代码：

<uses-sdk
    android:minSdkVersion="8"
    android:targetSdkVersion="16" />

我删除了这部分android:targetSdkVersion="16"，解析变得非常快

为什么 ？？

4

1 回答 1

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我发现在大文件上，XMLParser 的性能很差，而且非常消耗内存。特别是如果 xml 中的一个节点非常大，例如编码位图。想想看，它必须一次将整个字符串加载到内存中。我切换到自己解析文件，因为我只寻找一个特定部分并使用 BufferedInputStream 读取数据以避免内存峰值。

这可能不是您的问题，但要知道对于非常大的文件，XMLParser 不可用。

于 2013-01-25T23:38:53.600 回答