我是android和java的初学者编程所以请原谅我，如果代码是错误的。我只是想从一个url中获取一些xml，然后在logcat中显示它，但我一直得到同样的错误。
这是日志：
01-01 19:49:38.065: E/Trace(6471): error opening trace file: No such file or directory (2)
01-01 19:49:38.225: D/AndroidRuntime(6471): Shutting down VM
01-01 19:49:38.225: W/dalvikvm(6471): threadid=1: thread exiting with uncaught exception (group=0x40c72300)
01-01 19:49:38.795: E/AndroidRuntime(6471): FATAL EXCEPTION: main
01-01 19:49:38.795: E/AndroidRuntime(6471): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.alexisdelatorre.helloxml/com.alexisdelatorre.helloxml.MainActivity}: android.os.NetworkOnMainThreadException
01-01 19:49:38.795: E/AndroidRuntime(6471): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2059)
01-01 19:49:38.795: E/AndroidRuntime(6471): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2084)
01-01 19:49:38.795: E/AndroidRuntime(6471): at android.app.ActivityThread.access$600(ActivityThread.java:130)
01-01 19:49:38.795: E/AndroidRuntime(6471): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1195)
01-01 19:49:38.795: E/AndroidRuntime(6471): at android.os.Handler.dispatchMessage(Handler.java:99)
01-01 19:49:38.795: E/AndroidRuntime(6471): at android.os.Looper.loop(Looper.java:137)
01-01 19:49:38.795: E/AndroidRuntime(6471): at android.app.ActivityThread.main(ActivityThread.java:4745)
01-01 19:49:38.795: E/AndroidRuntime(6471): at java.lang.reflect.Method.invokeNative(Native Method)
01-01 19:49:38.795: E/AndroidRuntime(6471): at java.lang.reflect.Method.invoke(Method.java:511)
01-01 19:49:38.795: E/AndroidRuntime(6471): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
01-01 19:49:38.795: E/AndroidRuntime(6471): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
01-01 19:49:38.795: E/AndroidRuntime(6471): at dalvik.system.NativeStart.main(Native Method)
01-01 19:49:38.795: E/AndroidRuntime(6471): Caused by: android.os.NetworkOnMainThreadException
01-01 19:49:38.795: E/AndroidRuntime(6471): at android.os.StrictMode$AndroidBlockGuardPolicy.onNetwork(StrictMode.java:1117)
01-01 19:49:38.795: E/AndroidRuntime(6471): at java.net.InetAddress.lookupHostByName(InetAddress.java:385)
01-01 19:49:38.795: E/AndroidRuntime(6471): at java.net.InetAddress.getAllByNameImpl(InetAddress.java:236)
01-01 19:49:38.795: E/AndroidRuntime(6471): at java.net.InetAddress.getAllByName(InetAddress.java:214)
01-01 19:49:38.795: E/AndroidRuntime(6471): at org.apache.http.impl.conn.DefaultClientConnectionOperator.openConnection(DefaultClientConnectionOperator.java:137)
01-01 19:49:38.795: E/AndroidRuntime(6471): at org.apache.http.impl.conn.AbstractPoolEntry.open(AbstractPoolEntry.java:164)
01-01 19:49:38.795: E/AndroidRuntime(6471): at org.apache.http.impl.conn.AbstractPooledConnAdapter.open(AbstractPooledConnAdapter.java:119)
01-01 19:49:38.795: E/AndroidRuntime(6471): at org.apache.http.impl.client.DefaultRequestDirector.execute(DefaultRequestDirector.java:360)
01-01 19:49:38.795: E/AndroidRuntime(6471): at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:555)
01-01 19:49:38.795: E/AndroidRuntime(6471): at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:487)
01-01 19:49:38.795: E/AndroidRuntime(6471): at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:465)
01-01 19:49:38.795: E/AndroidRuntime(6471): at com.alexisdelatorre.helloxml.JavaXmlTutorial.getXmlFromUrl(JavaXmlTutorial.java:64)
01-01 19:49:38.795: E/AndroidRuntime(6471): at com.alexisdelatorre.helloxml.JavaXmlTutorial.<init>(JavaXmlTutorial.java:31)
01-01 19:49:38.795: E/AndroidRuntime(6471): at com.alexisdelatorre.helloxml.MainActivity.onCreate(MainActivity.java:21)
01-01 19:49:38.795: E/AndroidRuntime(6471): at android.app.Activity.performCreate(Activity.java:5008)
01-01 19:49:38.795: E/AndroidRuntime(6471): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1079)
01-01 19:49:38.795: E/AndroidRuntime(6471): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2023)
01-01 19:49:38.795: E/AndroidRuntime(6471): ... 11 more
代码：
package com.alexisdelatorre.helloxml;
import java.io.IOException;
public class JavaXmlTutorial {
public JavaXmlTutorial() throws XmlPullParserException, IOException{
String xmlFromUrl = getXmlFromUrl("http://api.androidhive.info/pizza/?format=xml");
XmlPullParserFactory factory = XmlPullParserFactory.newInstance();
factory.setNamespaceAware(true);
XmlPullParser xpp = factory.newPullParser();
xpp.setInput(new StringReader (xmlFromUrl));
int eventType = xpp.getEventType();
while (eventType != XmlPullParser.END_DOCUMENT) {
if(eventType == XmlPullParser.START_DOCUMENT) {
Log.d(TAGS.DEBUG, "start document");
} else if(eventType == XmlPullParser.END_DOCUMENT) {
Log.d(TAGS.DEBUG, "end document");
} else if(eventType == XmlPullParser.START_TAG) {
Log.d(TAGS.DEBUG,"Start tag "+xpp.getName());
} else if(eventType == XmlPullParser.END_TAG) {
Log.d(TAGS.DEBUG,"End tag "+xpp.getName());
} else if(eventType == XmlPullParser.TEXT) {
Log.d(TAGS.DEBUG,"Text "+xpp.getText());
}
eventType = xpp.next();
}
}
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;
}
}
答案 0 :(得分：0)
您无法在主线程上发出HTTP个请求，这会导致UI冻结。所以它会引发NetworkOnMainThreadException异常。您需要在AsyncTask或其他Thread中执行此操作。
查看NetworkOnMainThreadException
class SynchTask extends AsyncTask<Void,Void,Void>
{
protected void onPreExecute()
{ super.onPreExecute();
//display progressdialog.
}
protected void doInBackground(Void ...params)
{
//http request. do not update ui here
JavaXmlTutorial parse=new JavaXmlTutorial();
return null;
}
protected void onPostExecute(Void result)
{
super.onPostExecute(result);
//dismiss progressdialog.
//update ui
}
}