我正在做一个必须从网址获取XML文件并解析它的应用程序。我总是找到这个日志猫（PS：我找不到正确的谷歌美化sintax代码突出显示）：
11-06 23:12:44.940: E/Trace(8751): error opening trace file: No such file or directory(2)
11-06 23:12:51.345: E/Error:(8751): expected: /hr read: body (position:END_TAG </body>@6:8 in java.io.StringReader@431887b8)
11-06 23:12:51.360: E/AndroidRuntime(8751): FATAL EXCEPTION: AsyncTask #1
11-06 23:12:51.360: E/AndroidRuntime(8751): java.lang.RuntimeException: An error occured while executing doInBackground()
11-06 23:12:51.360: E/AndroidRuntime(8751): at android.os.AsyncTask$3.done(AsyncTask.java:299)
11-06 23:12:51.360: E/AndroidRuntime(8751): at java.util.concurrent.FutureTask$Sync.innerSetException(FutureTask.java:273)
11-06 23:12:51.360: E/AndroidRuntime(8751): at java.util.concurrent.FutureTask.setException(FutureTask.java:124)
11-06 23:12:51.360: E/AndroidRuntime(8751): at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:307)
11-06 23:12:51.360: E/AndroidRuntime(8751): at java.util.concurrent.FutureTask.run(FutureTask.java:137)
11-06 23:12:51.360: E/AndroidRuntime(8751): at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:230)
11-06 23:12:51.360: E/AndroidRuntime(8751): at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1076)
11-06 23:12:51.360: E/AndroidRuntime(8751): at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:569)
11-06 23:12:51.360: E/AndroidRuntime(8751): at java.lang.Thread.run(Thread.java:856)
11-06 23:12:51.360: E/AndroidRuntime(8751): Caused by: java.lang.NullPointerException
11-06 23:12:51.360: E/AndroidRuntime(8751): at com.ambro.app.Update$connection.doInBackground(Update.java:39)
11-06 23:12:51.360: E/AndroidRuntime(8751): at com.ambro.app.Update$connection.doInBackground(Update.java:1)
11-06 23:12:51.360: E/AndroidRuntime(8751): at android.os.AsyncTask$2.call(AsyncTask.java:287)
11-06 23:12:51.360: E/AndroidRuntime(8751): at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:305)
11-06 23:12:51.360: E/AndroidRuntime(8751): ... 5 more
可以在http://www.lookedpath.tk/apps/firstapp/version.xml
找到xmlupdate.java代码：
public class Update extends Activity {
private TextView testo2;
@Override
public void onCreate(Bundle savedInstanceState) {
setContentView(R.layout.update);
super.onCreate(savedInstanceState);
testo2= (TextView) findViewById(R.id.textView2);
}
public void goToUpdate (View view) {
System.out.println("ciao");
new connection().execute();
}
public class connection extends AsyncTask<Void, Void, Boolean> {
protected Boolean doInBackground(Void... params) {
boolean updated=false;
String lastversion=null;
Element e=null;
final String URL = "http://www.lookedpath.tk/apps/firstapp/version.xml";
final String VERSION = "version";
final String APPLICATION = "application";
XMLParser parser = new XMLParser();
String xml = parser.getXmlFromUrl(URL); // getting XML
Document doc = parser.getDomElement(xml); // getting DOM element
NodeList nl = doc.getElementsByTagName(APPLICATION);
for (int i=0;i<nl.getLength();i++) {
e = (Element) nl.item(0);
lastversion = parser.getValue(e, VERSION); // name child value
}
String actver = getString(R.string.version);
if(actver==lastversion) updated=true;
return updated;
}
protected void onPostExecute(Boolean... result) {
if(result[0]==false){
testo2.setText(R.string.newversion);
} else {
testo2.setText(R.string.nonewversion);
}
}
};
}
所以这是xmlparser.java文件：
public class XMLParser {
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;
}
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 DOM
return doc;
}
public String getValue(Element item, String str) {
NodeList n = item.getElementsByTagName(str);
return this.getElementValue(n.item(0));
}
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 "";
}
}
logcat说错误发生在更新类的第39行：
NodeList nl = doc.getElementsByTagName(APPLICATION);
但我无法解决问题。有谁可以帮助我？
更新 我修复了错误405，但我仍然有一个空指针异常。我发现该程序运行正常但从未进入post execute方法，因为这个例外..
答案 0 :(得分：3)
我试过你的代码没有任何问题，很好。问题出在链接中。
在浏览器中，它看起来像这样
<?xml version="1.0" encoding="UTF-8"?>
<menu>
<application>
<version>1.5</version>
</application>
</menu>
但是当我打印xml变量时，它会给我
<html>
<head><title>405 Not Allowed</title></head>
<body bgcolor="white">
<center><h1>405 Not Allowed</h1></center>
<hr><center>nginx</center>
</body>
</html>
然后在dom变量中你得到null，当你试图在nl变量中找到null的元素时你得到错误..，。
我尝试使用其他一些xml Feed的代码，它非常适用..，。
答案 1 :(得分：0)
嘿看看我的Library。
您可以使用它轻松操作XML;）
答案 2 :(得分：0)
您可以从xml检查此链接以进行xml解析。 http://www.androidhive.info/2012/02/android-custom-listview-with-image-and-text/
在您的活动中，您正在开发AsyncTask，但您忘记覆盖onPreExecute方法。请参阅此示例，了解如何在您的活动中开发AsyncTask。
package com.androidhive.jsonparsing;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.UnsupportedEncodingException;
import java.util.ArrayList;
import java.util.HashMap;
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.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import android.app.ListActivity;
import android.app.ProgressDialog;
import android.content.Intent;
import android.os.AsyncTask;
import android.os.Bundle;
import android.util.Log;
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 AndroidJSONParsingActivity extends ListActivity {
// url to make request
private static String url = "http://api.androidhive.info/contacts/";
// JSON Node names
private static final String TAG_CONTACTS = "contacts";
private static final String TAG_ID = "id";
private static final String TAG_NAME = "name";
private static final String TAG_EMAIL = "email";
private static final String TAG_ADDRESS = "address";
private static final String TAG_GENDER = "gender";
private static final String TAG_PHONE = "phone";
private static final String TAG_PHONE_MOBILE = "mobile";
private static final String TAG_PHONE_HOME = "home";
private static final String TAG_PHONE_OFFICE = "office";
static InputStream is = null;
static JSONObject jObj = null;
static String json = "";
// contacts JSONArray
JSONArray contacts = null;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
new GetEventsTask().execute("");
}
protected class GetEventsTask extends
AsyncTask<String, Integer, ArrayList<HashMap<String, String>>> {
protected ArrayList<HashMap<String, String>> contactList;
private final ProgressDialog dialog = new ProgressDialog(
AndroidJSONParsingActivity.this);
//PreExecute Method
protected void onPreExecute() {
this.dialog.setMessage("Loading, Please Wait..");
this.dialog.setCancelable(false);
this.dialog.show();
}
//doInBackground Method
@Override
protected ArrayList<HashMap<String, String>> doInBackground(
String... params) {
contactList = new ArrayList<HashMap<String, String>>();
// Making HTTP request
try {
// defaultHttpClient
DefaultHttpClient httpClient = new DefaultHttpClient();
HttpPost httpPost = new HttpPost(url);
HttpResponse httpResponse = httpClient.execute(httpPost);
HttpEntity httpEntity = httpResponse.getEntity();
is = httpEntity.getContent();
BufferedReader reader = new BufferedReader(
new InputStreamReader(is, "iso-8859-1"), 8);
StringBuilder sb = new StringBuilder();
String line = null;
while ((line = reader.readLine()) != null) {
sb.append(line + "\n");
}
is.close();
json = sb.toString();
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
} catch (ClientProtocolException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
// try parse the string to a JSON object
try {
jObj = new JSONObject(json);
Log.i("json objects",""+json);
} catch (JSONException e) {
Log.e("JSON Parser", "Error parsing data " + e.toString());
}
try {
// Getting Array of Contacts
contacts = jObj.getJSONArray(TAG_CONTACTS);
// looping through All Contacts
for (int i = 0; i < contacts.length(); i++) {
JSONObject c = contacts.getJSONObject(i);
// Storing each json item in variable
String id = c.getString(TAG_ID);
String name = c.getString(TAG_NAME);
String email = c.getString(TAG_EMAIL);
String address = c.getString(TAG_ADDRESS);
String gender = c.getString(TAG_GENDER);
// Phone number is agin JSON Object
JSONObject phone = c.getJSONObject(TAG_PHONE);
String mobile = phone.getString(TAG_PHONE_MOBILE);
String home = phone.getString(TAG_PHONE_HOME);
String office = phone.getString(TAG_PHONE_OFFICE);
// creating new HashMap
HashMap<String, String> map = new HashMap<String, String>();
// adding each child node to HashMap key => value
map.put(TAG_ID, id);
map.put(TAG_NAME, name);
map.put(TAG_EMAIL, email);
map.put(TAG_PHONE_MOBILE, mobile);
// adding HashList to ArrayList
contactList.add(map);
}
} catch (JSONException e) {
e.printStackTrace();
}
return contactList;
}
//onPostExecute Method
protected void onPostExecute(ArrayList<HashMap<String, String>> result) {
ListAdapter adapter = new SimpleAdapter(getApplicationContext(),
contactList, R.layout.list_item, new String[] { TAG_NAME,
TAG_EMAIL, TAG_PHONE_MOBILE }, new int[] {
R.id.name, R.id.email, R.id.mobile });
// selecting single ListView item
ListView lv = getListView();
lv.setAdapter(adapter);
// Launching new screen on Selecting Single ListItem
lv.setOnItemClickListener(new OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view,
int position, long id) {
// getting values from selected ListItem
String name = ((TextView) view.findViewById(R.id.name)).getText().toString();
String cost = ((TextView) view.findViewById(R.id.email)).getText().toString();
String description = ((TextView) view.findViewById(R.id.mobile)).getText().toString();
// Starting new intent
Intent in = new Intent(getApplicationContext(),SingleMenuItemActivity.class);
in.putExtra(TAG_NAME, name);
in.putExtra(TAG_EMAIL, cost);
in.putExtra(TAG_PHONE_MOBILE, description);
startActivity(in);
}
});
if (this.dialog.isShowing()) {
this.dialog.dismiss();
}
}
}
}
答案 3 :(得分：0)
你在那个位置只得到null xml来调试你的应用程序首先检查你得到的任何xml响应????
如果你得到null xml，那么使用以下代码来解析xml
import org.xml.sax.Attributes;
import org.xml.sax.SAXException;
import org.xml.sax.helpers.DefaultHandler;
import android.util.Log;
public class XMLHandler extends DefaultHandler {
String elementValue = null;
Boolean elementOn = false;
userdata d = userdata.getInstance();
public static XMLGettersSetters data = null;
public static XMLGettersSetters getXMLData() {
return data;
}
public static void setXMLData(XMLGettersSetters data) {
XMLHandler.data = data;
}
/**
* This will be called when the tags of the XML starts.
**/
@Override
public void startElement(String uri, String localName, String qName,
Attributes attributes) throws SAXException {
elementOn = true;
if (localName.equals("application"))
{
data = new XMLGettersSetters();
}
}
/**
* This will be called when the tags of the XML end.
**/
@Override
public void endElement(String uri, String localName, String qName)
throws SAXException {
elementOn = false;
/**
* Sets the values after retrieving the values from the XML tags
* */
if (localName.equalsIgnoreCase("version")){
System.out.println("ststus" + elementValue);
d.setIsregi(elementValue);
}
/**
* This is called to get the tags value
**/
@Override
public void characters(char[] ch, int start, int length)
throws SAXException {
if (elementOn) {
elementValue = new String(ch, start, length);
elementOn = false;
}
}
}
答案 4 :(得分：0)
您必须将正确的DTD添加到xml（文档类型定义），尝试它，您将看到解析将顺利运行。 第1步：生成纠正DTD 第2步：将其添加到您的xml文件并保存 第3步：上传您的xml文件，解析并享受。