我的应用程序从新闻网页下载标题并将其显示在列表视图中，有点像RSSReader，现在当我尝试运行它但显示错误时。
代码： -
public class RSSReaderActivity extends ListActivity
{ List headlines, links;
@Override
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
new DoSomeTask().execute();
}
// DoSomeTask class will do all the work on another thread so there will be no
// ANR and UI hanging.
private class DoSomeTask extends AsyncTask<Void, Void, Void>
{
/* (non-Javadoc)
* @see android.os.AsyncTask#doInBackground(Params[])
*/
@Override
protected Void doInBackground(Void... arg0) {
try {
headlines = new ArrayList();
links = new ArrayList();
URL url = new URL("http://feeds.pcworld.com/pcworld/latestnews");
XmlPullParserFactory factory = XmlPullParserFactory.newInstance();
factory.setNamespaceAware(false);
XmlPullParser xpp = factory.newPullParser();
// We will get the XML from an input stream
xpp.setInput(getInputStream(url), "UTF_8");
boolean insideItem = false;
// Returns the type of current event: START_TAG, END_TAG, etc..
int eventType = xpp.getEventType();
while (eventType != XmlPullParser.END_DOCUMENT)
{
if (eventType == XmlPullParser.START_TAG)
{
if (xpp.getName().equalsIgnoreCase("item"))
{
insideItem = true;
}
else if (xpp.getName().equalsIgnoreCase("title"))
{
if (insideItem)
headlines.add(xpp.nextText()); //extract the headline
}
else if (xpp.getName().equalsIgnoreCase("link"))
{
if (insideItem)
links.add(xpp.nextText()); //extract the link of article
}
}
else if(eventType==XmlPullParser.END_TAG && xpp.getName().equalsIgnoreCase("item"))
{
insideItem=false;
}
eventType = xpp.next(); //move to next element
}
} catch (MalformedURLException e) {
e.printStackTrace();
} catch (XmlPullParserException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
return null;
}
protected void onPostExecute(Void params)
{
try{
// Binding data
ArrayAdapter adapter = new ArrayAdapter(RSSReaderActivity.this,
android.R.layout.simple_list_item_1, headlines);
setListAdapter(adapter);
}catch (Exception e) {}
}
}
public InputStream getInputStream(URL url) {
try {
return url.openConnection().getInputStream();
} catch (IOException e) {
return null;
}
}
protected void onListItemClick(ListView l, View v, int position, long id) {
Uri uri = Uri.parse((String) links.get(position));
Intent intent = new Intent(Intent.ACTION_VIEW, uri);
startActivity(intent);
}
}
logcat的： -
06-23 19:37:57.505: W/dalvikvm(7450): threadid=8: thread exiting with uncaught exception (group=0x400207d8)
06-23 19:37:57.785: E/AndroidRuntime(7450): FATAL EXCEPTION: AsyncTask #1
06-23 19:37:57.785: E/AndroidRuntime(7450): java.lang.RuntimeException: An error occured while executing doInBackground()
06-23 19:37:57.785: E/AndroidRuntime(7450): at android.os.AsyncTask$3.done(AsyncTask.java:200)
06-23 19:37:57.785: E/AndroidRuntime(7450): at java.util.concurrent.FutureTask$Sync.innerSetException(FutureTask.java:273)
06-23 19:37:57.785: E/AndroidRuntime(7450): at java.util.concurrent.FutureTask.setException(FutureTask.java:124)
06-23 19:37:57.785: E/AndroidRuntime(7450): at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:307)
06-23 19:37:57.785: E/AndroidRuntime(7450): at java.util.concurrent.FutureTask.run(FutureTask.java:137)
06-23 19:37:57.785: E/AndroidRuntime(7450): at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1068)
06-23 19:37:57.785: E/AndroidRuntime(7450): at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:561)
06-23 19:37:57.785: E/AndroidRuntime(7450): at java.lang.Thread.run(Thread.java:1096)
06-23 19:37:57.785: E/AndroidRuntime(7450): Caused by: java.lang.IllegalArgumentException
06-23 19:37:57.785: E/AndroidRuntime(7450): at org.kxml2.io.KXmlParser.setInput(KXmlParser.java:1040)
06-23 19:37:57.785: E/AndroidRuntime(7450): at mohit.apps.rssreaderfast.RSSReaderActivity$DoSomeTask.doInBackground(RSSReaderActivity.java:56)
06-23 19:37:57.785: E/AndroidRuntime(7450): at mohit.apps.rssreaderfast.RSSReaderActivity$DoSomeTask.doInBackground(RSSReaderActivity.java:1)
06-23 19:37:57.785: E/AndroidRuntime(7450): at android.os.AsyncTask$2.call(AsyncTask.java:185)
06-23 19:37:57.785: E/AndroidRuntime(7450): at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:305)
06-23 19:37:57.785: E/AndroidRuntime(7450): ... 4 more
所以是的，错误是在doInBackground（）中，因为我是新的多线程编程，请指出我的代码问题是什么。感谢。
答案 0 :(得分：1)
问题很可能出在这段代码的某处：
try {
return url.openConnection().getInputStream();
} catch (IOException e) {
return null;
}
来自KXmlParser的源代码：
if (is == null)
throw new IllegalArgumentException();
正在发生的事情是在调用url.openConnection().getInputStream();时抛出异常导致方法返回null，而XMLPullParser的setInput反过来又抛出InvalidArgumentException，从源头看。尝试将catch块中的stacktrace打印到控制台(Log.e("some_tag", "some message", e);，然后返回null并查看异常是什么，并从那里开始。
另外，要解决“UTF_8”与“UTF-8”辩论，另一张海报出现了，只需使用xpp.setInput(getInputStream(url), HTTP.UTF_8);
答案 1 :(得分：1)
以下行中有错误
xpp.setInput(getInputStream(url), "UTF_8");
将UTF_8替换为UTF-8
同时删除setContentView(R.layout.main);
下面是snippt。
package org.sample;
import java.io.IOException;
import java.io.InputStream;
import java.net.MalformedURLException;
import java.net.URL;
import java.util.ArrayList;
import java.util.List;
import org.xmlpull.v1.XmlPullParser;
import org.xmlpull.v1.XmlPullParserException;
import org.xmlpull.v1.XmlPullParserFactory;
import android.app.ListActivity;
import android.content.Intent;
import android.net.Uri;
import android.os.AsyncTask;
import android.os.Bundle;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.ListView;
public class SampleActivity extends ListActivity {
List headlines, links;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
new DoSomeTask().execute();
}
// DoSomeTask class will do all the work on another thread so there will be
// no
// ANR and UI hanging.
private class DoSomeTask extends AsyncTask<Void, Void, Void> {
/*
* (non-Javadoc)
*
* @see android.os.AsyncTask#doInBackground(Params[])
*/
@Override
protected Void doInBackground(Void... arg0) {
try {
headlines = new ArrayList();
links = new ArrayList();
URL url = new URL("http://feeds.pcworld.com/pcworld/latestnews");
XmlPullParserFactory factory = XmlPullParserFactory
.newInstance();
factory.setNamespaceAware(false);
XmlPullParser xpp = factory.newPullParser();
// We will get the XML from an input stream
xpp.setInput(getInputStream(url), "UTF-8");
boolean insideItem = false;
// Returns the type of current event: START_TAG, END_TAG, etc..
int eventType = xpp.getEventType();
while (eventType != XmlPullParser.END_DOCUMENT) {
if (eventType == XmlPullParser.START_TAG) {
if (xpp.getName().equalsIgnoreCase("item")) {
insideItem = true;
} else if (xpp.getName().equalsIgnoreCase("title")) {
if (insideItem)
headlines.add(xpp.nextText()); // extract the
// headline
} else if (xpp.getName().equalsIgnoreCase("link")) {
if (insideItem)
links.add(xpp.nextText()); // extract the link
// of article
}
} else if (eventType == XmlPullParser.END_TAG
&& xpp.getName().equalsIgnoreCase("item")) {
insideItem = false;
}
eventType = xpp.next(); // move to next element
}
} catch (MalformedURLException e) {
e.printStackTrace();
} catch (XmlPullParserException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
return null;
}
protected void onPostExecute(Void params) {
try {
// Binding data
ArrayAdapter adapter = new ArrayAdapter(AbcActivity.this,
android.R.layout.simple_list_item_1, headlines);
setListAdapter(adapter);
} catch (Exception e) {
}
}
}
public InputStream getInputStream(URL url) {
try {
return url.openConnection().getInputStream();
} catch (IOException e) {
return null;
}
}
protected void onListItemClick(ListView l, View v, int position, long id) {
Uri uri = Uri.parse((String) links.get(position));
Intent intent = new Intent(Intent.ACTION_VIEW, uri);
startActivity(intent);
}
}
答案 2 :(得分：-1)
Phew ... atlast its fixed。
我刚刚改变了
xpp.setInput(getInputStream(url), "UTF_8");
到
xpp.setInput(url.openConnection().getInputStream(), "UTF_8");
和Viola：）