java - XML 解析失败

Question

我正在为 Android 中的 XML 解析器编写应用程序但是当我下载代码并运行它时，它运行完美， 但是我写了同样的代码却不起作用，为什么会这样？

这有什么先决条件吗？请帮我解决这个问题

我在 XMLParser.java 中遇到错误

package com.xmlparser;
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));
        }
}

我的日志猫

11-22 15:35:53.675: E/AndroidRuntime(19208): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.xmlparser/com.xmlparser.Xparser}: android.os.NetworkOnMainThreadException
11-22 15:35:53.675: E/AndroidRuntime(19208):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2100)
11-22 15:35:53.675: E/AndroidRuntime(19208):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2125)
11-22 15:35:53.675: E/AndroidRuntime(19208):    at android.app.ActivityThread.access$600(ActivityThread.java:140)
11-22 15:35:53.675: E/AndroidRuntime(19208):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1227)
11-22 15:35:53.675: E/AndroidRuntime(19208):    at android.os.Handler.dispatchMessage(Handler.java:99)
11-22 15:35:53.675: E/AndroidRuntime(19208):    at android.os.Looper.loop(Looper.java:137)
11-22 15:35:53.675: E/AndroidRuntime(19208):    at android.app.ActivityThread.main(ActivityThread.java:4898)
11-22 15:35:53.675: E/AndroidRuntime(19208):    at java.lang.reflect.Method.invokeNative(Native Method)
11-22 15:35:53.675: E/AndroidRuntime(19208):    at java.lang.reflect.Method.invoke(Method.java:511)
11-22 15:35:53.675: E/AndroidRuntime(19208):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1008)
11-22 15:35:53.675: E/AndroidRuntime(19208):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:775)
11-22 15:35:53.675: E/AndroidRuntime(19208):    at dalvik.system.NativeStart.main(Native Method)
11-22 15:35:53.675: E/AndroidRuntime(19208): Caused by: android.os.NetworkOnMainThreadException
11-22 15:35:53.675: E/AndroidRuntime(19208):    at android.os.StrictMode$AndroidBlockGuardPolicy.onNetwork(StrictMode.java:1118)

    11-22 15:19:21.500: E/AndroidRuntime(16631):    at java.net.InetAddress.lookupHostByName(InetAddress.java:385)
    11-22 15:19:21.500: E/AndroidRuntime(16631):    at java.net.InetAddress.getAllByNameImpl(InetAddress.java:236)
    11-22 15:19:21.500: E/AndroidRuntime(16631):    at java.net.InetAddress.getAllByName(InetAddress.java:214)
    11-22 15:19:21.500: E/AndroidRuntime(16631):    at org.apache.http.impl.conn.DefaultClientConnectionOperator.openConnection(DefaultClientConnectionOperator.java:137)
    11-22 15:19:21.500: E/AndroidRuntime(16631):    at org.apache.http.impl.conn.AbstractPoolEntry.open(AbstractPoolEntry.java:164)
    11-22 15:19:21.500: E/AndroidRuntime(16631):    at org.apache.http.impl.conn.AbstractPooledConnAdapter.open(AbstractPooledConnAdapter.java:119)
    11-22 15:19:21.500: E/AndroidRuntime(16631):    at org.apache.http.impl.client.DefaultRequestDirector.execute(DefaultRequestDirector.java:360)
    11-22 15:19:21.500: E/AndroidRuntime(16631):    at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:670)
    11-22 15:19:21.500: E/AndroidRuntime(16631):    at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:509)
    11-22 15:19:21.500: E/AndroidRuntime(16631):    at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:487)
    11-22 15:19:21.500: E/AndroidRuntime(16631):    at com.xmlparser.XMLParser.getXmlFromUrl(XMLParser.java:45)
    11-22 15:19:21.500: E/AndroidRuntime(16631):    at com.xmlparser.Xparser.onCreate(Xparser.java:37)
    11-22 15:19:21.500: E/AndroidRuntime(16631):    at android.app.Activity.performCreate(Activity.java:5206)
    11-22 15:19:21.500: E/AndroidRuntime(16631):    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1094)
    11-22 15:19:21.500: E/AndroidRuntime(16631):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2064)

这是我的 Xparser.java

package com.xmlparser;

import java.util.ArrayList;
import java.util.HashMap;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.NodeList;

import android.app.ListActivity;
import android.content.Intent;
import android.os.Bundle;
import android.view.Menu;
import android.view.View;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.ListAdapter;
import android.widget.ListView;
import android.widget.SimpleAdapter;
import android.widget.TextView;

public class Xparser extends ListActivity {
    static final String URL = "http://api.androidhive.info/pizza/?format=xml";
    // XML key nodes
    static final String KEY_ITEM = "item";
    static final String KEY_ID = "id";
    static final String KEY_NAME = "name";
    static final String KEY_COST = "cost";
    static final String KEY_DESC = "description";


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_xmlparser);
        ArrayList<HashMap<String, String>> menuItems = new ArrayList<HashMap<String, String>>();
        XMLParser parser = new XMLParser();
        String xml = parser.getXmlFromUrl(URL);// getting XML
        Document doc = parser.getDomElement(xml);// getting Dom Element

        NodeList n1 = doc.getElementsByTagName(KEY_ITEM);
         // looping through all item nodes <item>
        for(int i=0 ; i < n1.getLength(); i++){
            HashMap<String,String> map = new HashMap<String,String>();
            Element e = (Element) n1.item(i);
            //adding each child to Hashmap node key
            map.put(KEY_ID, parser.getValue(e,KEY_ID));
            map.put(KEY_NAME, parser.getValue(e,KEY_NAME));
            map.put(KEY_COST, "Rs."+ parser.getValue(e,KEY_COST));
            map.put(KEY_DESC, parser.getValue(e,KEY_DESC));

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

    // Adding menuItems to ListView
        ListAdapter adapter = new SimpleAdapter(this, menuItems,
                R.layout.list_select_item,
                new String[] { KEY_NAME, KEY_DESC, KEY_COST }, new int[] {
                        R.id.name, R.id.desciption, R.id.cost });
    setListAdapter(adapter);


    // selecting single ListView item
    ListView lv = getListView();
    lv.setOnItemClickListener(new OnItemClickListener(){
    @Override
    public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
        // TODO Auto-generated method stub
        String name = ((TextView) view.findViewById(R.id.name)).getText().toString();
        String cost = ((TextView) view.findViewById(R.id.cost)).getText().toString();
        String desc = ((TextView) view.findViewById(R.id.desciption)).getText().toString();

        Intent in = new Intent();
        in.putExtra(KEY_NAME, name);
        in.putExtra(KEY_DESC, desc);
        in.putExtra(KEY_COST, cost);
        startActivity(in);
    }

    });
    }
    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.xmlparser, menu);
        return true;
        }
}

Answer 1

异常tells you everything你得知道。您正在尝试在主线程上提交数据。在单独的线程中执行网络操作。

There's a link in the docs that explains it , 和 this might help you to move on .