BufferedReader抛出异常，我不知道为什么

public URL setUrl() throws Exception{ 
    System.out.println("1"); 
    URL iotd=new URL("http://www.nasa.gov/rss/image_of_the_day.rss"); 
    System.out.println("2"); 
    BufferedReader in=new BufferedReader(new InputStreamReader(iotd.openStream())); 
    System.out.println("3");**//this never gets printed** 

    //testing xml parser 
    XmlPullParserFactory factory=XmlPullParserFactory.newInstance(); 
    factory.setNamespaceAware(true); 
    System.out.println("4"); 
    XmlPullParser xpp=factory.newPullParser(); 
    System.out.println("5"); 
    xpp.setInput(in); 
    System.out.println("6"); 

    int eventType=xpp.getEventType(); 
    System.out.println(eventType+"!!!!!!!!!!!!!!!!"); 
    while(eventType!=XmlPullParser.END_DOCUMENT){ 
     if(eventType==XmlPullParser.START_DOCUMENT){ 
      System.out.println("start"); 
     } 
    } 

    in.close(); 
    return iotd; 

}

该程序从来没有打印出“3”和这么多的警告在logcat中，这是很难破译发生了什么事情，因为我没有用过Java相当一段时间。有任何想法吗？我下面这个代码示例...BufferedReader抛出异常，我不知道为什么

http://docs.oracle.com/javase/tutorial/networking/urls/readingURL.html

，并试图修改它来解析XML，但我还没有得到测试的那部分呢。

这里是所有的logcat给我打印 “2”

07-10 05:31:30.610: W/System.err(534): android.os.NetworkOnMainThreadException 
07-10 05:31:30.621: W/System.err(534): at android.os.StrictMode$AndroidBlockGuardPolicy.onNetwork(StrictMode.java:1099) 
07-10 05:31:30.621: W/System.err(534): at java.net.InetAddress.lookupHostByName(InetAddress.java:391) 
07-10 05:31:30.621: W/System.err(534): at java.net.InetAddress.getAllByNameImpl(InetAddress.java:242) 
07-10 05:31:30.621: W/System.err(534): at java.net.InetAddress.getAllByName(InetAddress.java:220) 
07-10 05:31:30.621: W/System.err(534): at libcore.net.http.HttpConnection.<init>(HttpConnection.java:71) 
07-10 05:31:30.621: W/System.err(534): at libcore.net.http.HttpConnection.<init>(HttpConnection.java:50) 
07-10 05:31:30.621: W/System.err(534): at libcore.net.http.HttpConnection$Address.connect(HttpConnection.java:351) 
07-10 05:31:30.621: W/System.err(534): at libcore.net.http.HttpConnectionPool.get(HttpConnectionPool.java:86) 
07-10 05:31:30.621: W/System.err(534): at libcore.net.http.HttpConnection.connect(HttpConnection.java:128) 
07-10 05:31:30.630: W/System.err(534): at libcore.net.http.HttpEngine.openSocketConnection(HttpEngine.java:308) 
07-10 05:31:30.630: W/System.err(534): at libcore.net.http.HttpEngine.connect(HttpEngine.java:303) 
07-10 05:31:30.630: W/System.err(534): at libcore.net.http.HttpEngine.sendSocketRequest(HttpEngine.java:282) 
07-10 05:31:30.630: W/System.err(534): at libcore.net.http.HttpEngine.sendRequest(HttpEngine.java:232) 
07-10 05:31:30.630: W/System.err(534): at libcore.net.http.HttpURLConnectionImpl.getResponse(HttpURLConnectionImpl.java:273) 
07-10 05:31:30.630: W/System.err(534): at libcore.net.http.HttpURLConnectionImpl.getInputStream(HttpURLConnectionImpl.java:168) 
07-10 05:31:30.630: W/System.err(534): at java.net.URL.openStream(URL.java:462) 
07-10 05:31:30.630: W/System.err(534): at com.wajumbie.nasadailyimage.RssParse.setUrl(RssParse.java:14) 
07-10 05:31:30.630: W/System.err(534): at com.wajumbie.nasadailyimage.NasaDailyImage.onCreate(NasaDailyImage.java:29) 
07-10 05:31:30.630: W/System.err(534): at android.app.Activity.performCreate(Activity.java:4465) 
07-10 05:31:30.630: W/System.err(534): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1049) 
07-10 05:31:30.630: W/System.err(534): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1920) 
07-10 05:31:30.630: W/System.err(534): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1981) 
07-10 05:31:30.640: W/System.err(534): at android.app.ActivityThread.access$600(ActivityThread.java:123) 
07-10 05:31:30.640: W/System.err(534): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1147) 
07-10 05:31:30.640: W/System.err(534): at android.os.Handler.dispatchMessage(Handler.java:99) 
07-10 05:31:30.640: W/System.err(534): at android.os.Looper.loop(Looper.java:137) 
07-10 05:31:30.640: W/System.err(534): at android.app.ActivityThread.main(ActivityThread.java:4424) 
07-10 05:31:30.640: W/System.err(534): at java.lang.reflect.Method.invokeNative(Native Method) 
07-10 05:31:30.640: W/System.err(534): at java.lang.reflect.Method.invoke(Method.java:511) 
07-10 05:31:30.640: W/System.err(534): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784) 
07-10 05:31:30.640: W/System.err(534): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551) 
07-10 05:31:30.640: W/System.err(534): at dalvik.system.NativeStart.main(Native Method)

来源

2012-07-10 Tyler Pfaff

请提供堆栈跟踪。 – keuleJ 2012-07-10 06:12:57

我如何从logcat中取出它？编辑：从来没有想过它 – 2012-07-10 06:14:06

'NetworkOnMainThreadException'应该是一个大提示。查看它！ – 2012-07-10 06:24:08

有一个NetworkOnMainThreadException之后的警告。阅读this link了解更多信息。还有this article。

来源

2012-07-10 06:25:21 hage

谢谢！我会尽量把它放在一个新的线程中。 – 2012-07-10 06:43:14

尝试这种方式

InputStream is=callWebservice("http://www.nasa.gov/rss/image_of_the_day.rss"); 
BufferedReader in=new BufferedReader(new InputStreamReader(
      is, "iso-8859-1"));

其中callWebservice是如下图所示

private InputStream callWebservice(String serviceURL) { 
     HttpClient client=new DefaultHttpClient(); 
     HttpGet getRequest=new HttpGet(); 

     try { 
      // construct a URI object 
      getRequest.setURI(new URI(serviceURL)); 
     } catch (URISyntaxException e) { 
      Log.e("URISyntaxException", e.toString()); 
     } 

     // buffer reader to read the response 
     BufferedReader in=null; 
     // the service response 
     HttpResponse response=null; 
     try { 
      // execute the request 
      response = client.execute(getRequest); 
     } catch (ClientProtocolException e) { 
      Log.e("ClientProtocolException", e.toString()); 
     } catch (IOException e) { 
      Log.e("IO exception", e.toString()); 
     } 
     if(response!=null) 
      try { 
       return response.getEntity().getContent(); 
      } catch (IllegalStateException e) { 
       // TODO Auto-generated catch block 

       e.printStackTrace(); 
      } catch (IOException e) { 
       // TODO Auto-generated catch block 

       e.printStackTrace(); 
      } 
     else 
      return null; 
     return null; 

    }

来源

2012-07-10 06:26:07 Khan

的异常堆栈跟踪表明您在主线程上运行此。是这样吗？ Android开发的主线程不应该有网络或磁盘访问。你应该将网络操作移动到一个线程，然后严格的模式守卫不会导致异常。

来源

2012-07-10 06:28:11

BufferedReader抛出异常，我不知道为什么

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