HttpResponse使用android问题:执行总是导致exception?

我一直在研究一个Android项目,我想要一些API来获取信息。 看起来这应该是非常基本的!

这是我的代码的一般要点:

private InputStream retrieveStream2(String url) { DefaultHttpClient client = new DefaultHttpClient(); HttpGet getRequest = new HttpGet(url); System.out.println("getRequest == " + getRequest); try { HttpResponse getResponse = client.execute(getRequest);//here is teh problem final int statusCode = getResponse.getStatusLine().getStatusCode(); if (statusCode != HttpStatus.SC_OK) { Log.w(getClass().getSimpleName(), "Error " + statusCode + " for URL " + url); return null; } HttpEntity getResponseEntity = getResponse.getEntity(); return getResponseEntity.getContent(); } catch (Exception e) { getRequest.abort(); Log.w(getClass().getSimpleName(), "Error for URL, YO " + url, e); } return null; } 

其中urlvariables是字符串“http://search.twitter.com/search.json?q=javacodegeeks”。

正如您所看到的那样,该网站上有一些不错的JSON信息; 我的问题是,每次调用’client.execute(getRequest);”时,程序都会抛出并捕获exception。 没有用!

我听说过两件事:

1)您必须为模拟器/设备设置使用互联网的权限! – 我想我已经覆盖了这个,但也许我做错了! 在我添加的androidmanifest.xml中

  

就是这样。

2)(我不太确定)你不能在’ui’线程中启动’网络’线程。 我不完全确定这意味着什么,但我继续前进并遵循Android Threads,Handlers和AsyncTasks的一些教程。 这里:请查看我遵循的AsyncTask教程下的代码:

http://www.vogella.de/articles/AndroidPerformance/article.html

继AsyncTask教程之后,我发现我仍然遇到了同样的问题 –

行:HttpGet httpGet = new HttpGet(url)总是抛出一个exception,就像之前一样。

这是我尝试上面的线程教程的logcat:

 02-27 20:43:28.565: I/ActivityManager(92): START {cmp=com.Prometheus.R1/.JsonParsingActivity} from pid 574 02-27 20:43:28.565: W/WindowManager(92): Failure taking screenshot for (180x300) to layer 21010 02-27 20:43:28.896: I/System.out(574): pre execute 02-27 20:43:29.236: I/ActivityManager(92): Displayed com.Prometheus.R1/.JsonParsingActivity: +638ms 02-27 20:43:29.329: I/ARMAssembler(35): generated scanline__00000077:03010104_00008001_00000000 [ 89 ipp] (110 ins) at [0x40fad6a8:0x40fad860] in 7204915 ns 02-27 20:43:30.016: W/System.err(574): java.net.UnknownHostException: Unable to resolve host "search.twitter.com": No address associated with hostname 02-27 20:43:30.016: W/System.err(574): at java.net.InetAddress.lookupHostByName(InetAddress.java:426) 02-27 20:43:30.026: W/System.err(574): at java.net.InetAddress.getAllByNameImpl(InetAddress.java:242) 02-27 20:43:30.026: W/System.err(574): at java.net.InetAddress.getAllByName(InetAddress.java:220) 02-27 20:43:30.026: W/System.err(574): at org.apache.http.impl.conn.DefaultClientConnectionOperator.openConnection(DefaultClientConnectionOperator.java:137) 02-27 20:43:30.036: W/System.err(574): at org.apache.http.impl.conn.AbstractPoolEntry.open(AbstractPoolEntry.java:164) 02-27 20:43:30.036: W/System.err(574): at org.apache.http.impl.conn.AbstractPooledConnAdapter.open(AbstractPooledConnAdapter.java:119) 02-27 20:43:30.046: W/System.err(574): at org.apache.http.impl.client.DefaultRequestDirector.execute(DefaultRequestDirector.java:360) 02-27 20:43:30.046: W/System.err(574): at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:555) 02-27 20:43:30.046: W/System.err(574): at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:487) 02-27 20:43:30.055: W/System.err(574): at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:465) 02-27 20:43:30.055: W/System.err(574): at com.Prometheus.R1.JsonParsingActivity$DownloadWebPageTask.doInBackground(JsonParsingActivity.java:88) 02-27 20:43:30.055: W/System.err(574): at com.Prometheus.R1.JsonParsingActivity$DownloadWebPageTask.doInBackground(JsonParsingActivity.java:1) 02-27 20:43:30.055: W/System.err(574): at android.os.AsyncTask$2.call(AsyncTask.java:264)
02-27 20:43:30.066: W/System.err(574): at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:305) 02-27 20:43:30.066: W/System.err(574): at java.util.concurrent.FutureTask.run(FutureTask.java:137)
02-27 20:43:30.066: W/System.err(574): at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:208) 02-27 20:43:30.076: W/System.err(574): at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1076) 02-27 20:43:30.076: W/System.err(574): at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:569) 02-27 20:43:30.087: W/System.err(574): at java.lang.Thread.run(Thread.java:856) 02-27 20:43:30.108: W/System.err(574): Caused by: libcore.io.GaiException: getaddrinfo failed: EAI_NODATA (No address associated with hostname) 02-27 20:43:30.116: W/System.err(574): at libcore.io.Posix.getaddrinfo(Native Method) 02-27 20:43:30.116: W/System.err(574): at libcore.io.ForwardingOs.getaddrinfo(ForwardingOs.java:55) 02-27 20:43:30.126: W/System.err(574): at java.net.InetAddress.lookupHostByName(InetAddress.java:411) 02-27 20:43:30.126: W/System.err(574): ... 18 more 02-27 20:43:30.136: I/System.out(574): Except thrown by url http://search.twitter.com/search.json?q=javacodegeeks, .... 02-27 20:43:30.136: I/System.out(574): response =

您可以看到exception是UnknownHostException:
“ava.net.UnknownHostException:无法解析主机”search.twitter.com“:没有与主机名关联的地址”
但我不认为这个网站是不可接受的……

任何人都可以告诉我发生了什么+我需要做些什么来度过难关?

检查清单的权限,确保添加了以下内容:

    

弄清楚了。 显然我把AVD从“飞机模式”上移开了。

对于任何与我有同样问题的人,你可能正在使用无线技术。 由于某种原因,andriod会查看您的LAN卡,因此请转到您的网络连接并右键单击LAN卡 – 禁用该function! 问题解决了。

我认为问题在于您在http请求或互联网连接中提供的URL请检查以下链接它将帮助您链接

我也遇到了这个问题。 在我的例子中,我使用HttpURLConnection来加载JSON。 当我启用“关注重定向”时,问题已得到解决。 这是一个有效的代码片段:

  HttpURLConnection connection = null; BufferedReader reader = null; String JSON_data = null; try { final int half_hour = 30 * 60; URL fetch = new URL(requestUrl); connection = (HttpURLConnection) fetch.openConnection(); // FIXED: request to follow redirects - this seems to solve networking issues on older devices < API 21 connection.setInstanceFollowRedirects(true); connection.setUseCaches(true); connection.setDefaultUseCaches(true); connection.setRequestMethod("GET"); connection.addRequestProperty("Cache-Control", "max-age="+half_hour); connection.addRequestProperty("X-Auth-Token", getString(R.string.api_key)); boolean redirect = false; int status = connection.getResponseCode(); if (status != HttpURLConnection.HTTP_OK) { if (status == HttpURLConnection.HTTP_MOVED_TEMP || status == HttpURLConnection.HTTP_MOVED_PERM || status == HttpURLConnection.HTTP_SEE_OTHER) redirect = true; } Log.d(TAG, "===> HTTP STATUS CODE: " + status + ", redirect=" + redirect); connection.connect(); // Read the input stream into a String InputStream inputStream = connection.getInputStream(); if (inputStream == null) { return; } reader = new BufferedReader(new InputStreamReader(inputStream)); StringBuilder buffer = new StringBuilder(); String line; while ((line = reader.readLine()) != null) { buffer.append(line); buffer.append("\n"); } if (buffer.length() == 0) { return; } JSON_data = buffer.toString(); Log.d(TAG, "JSON_data=" + JSON_data); } catch (Exception e) { // possible UnknownHostException on older Android device? Log.e(TAG, "HttpURLConnection Exception - e=" + e.getMessage()); e.printStackTrace(); } finally { if (connection != null) { connection.disconnect(); } if (reader != null) { try { reader.close(); } catch (IOException e) { Log.e(TAG, "Error closing stream - e=" + e.getMessage()); } } } 

您可以通过以下代码段在主线程中允许网络访问。 在您的活动的onCreate()方法的开头。

 StrictMode.ThreadPolicy policy = new StrictMode. ThreadPolicy.Builder().permitAll().build(); StrictMode.setThreadPolicy(policy);