为什么我用AsyncTask获取android.os.NetworkOnMainThreadException（） _AsyncTask

天下之事常成于困约，而败于奢靡。这篇文章主要讲述为什么我用AsyncTask获取android.os.NetworkOnMainThreadException？相关的知识，希望能为你提供帮助。
我在AsynkTask中编写了网络操作代码时得到了android.os.NetworkOnMainThreadException。抛出这个例外有什么其他原因吗？
这是我的代码：

public class Background_confirmation extends AsyncTask< Void, Integer, Void> { @Override protected void onPreExecute() { // TODO Auto-generated method stub progressDialog = ProgressDialog.show(Confirmation.this, "Please wait...", "Retrieving data ...", true); try { HttpClient httpclient = new DefaultHttpClient(); HttpPost httppost = new HttpPost( "http://68.121.167.160/sip_chat_api/create_account.php?useralias=" + useralias + "& cntname=" + cntcode + ""); HttpResponse response = httpclient.execute(httppost); HttpEntity entity = response.getEntity(); is = entity.getContent(); } catch (Exception e) { e.printStackTrace(); } if (backgroung_flag == 1) {} else { if (is != null) { try { BufferedReader reader = new BufferedReader( new InputStreamReader(is, "UTF-8")); StringBuilder sb = new StringBuilder(); String line = null; while ((line = reader.readLine()) != null) { sb.append(line + " "); } is.close(); result = sb.toString(); } catch (Exception e) { Log.e("log_tag", "Error converting result " + e.toString()); } }} super.onPreExecute(); }@Override protected Void doInBackground(Void... params) { // TODO Auto-generated method stubreturn null; }@Override protected void onPostExecute(Void result) { // TODO Auto-generated method stub if (progressDialog.isShowing()) { progressDialog.dismiss(); // progressDialog.setCancelable(true); } super.onPostExecute(result); }}

我在OnCreate（）中调用此类

new Background_confirmation().execute();

但它总是在Catch块中，并给我this例外LogCat 任何建议和想法都将得到赞赏。谢谢
答案

public class Background_confirmation extends AsyncTask< Void, Integer, String> { @Override protected void onPreExecute() { super.onPreExecute(); progressDialog = ProgressDialog.show(Confirmation.this, "Please wait...", "Retrieving data ...", true); }@Override protected String doInBackground(Void... params) {try { HttpClient httpclient = new DefaultHttpClient(); HttpPost httppost = new HttpPost("http://68.121.167.160/sip_chat_api/create_account.php?useralias=" + useralias + "& cntname=" + cntcode + ""); HttpResponse response = httpclient.execute(httppost); HttpEntity entity = response.getEntity(); is = entity.getContent(); } catch (Exception e) { e.printStackTrace(); } if (backgroung_flag == 1) {} else { if (is != null) { try { BufferedReader reader = new BufferedReader(new InputStreamReader(is, "UTF-8")); StringBuilder sb = new StringBuilder(); String line = null; while ((line = reader.readLine()) != null) { sb.append(line + " "); } is.close(); result = sb.toString(); } catch (Exception e) { Log.e("log_tag", "Error converting result " + e.toString()); } } } return result; }@Override protected void onPostExecute(String result) { super.onPostExecute(result); if (progressDialog.isShowing()) { progressDialog.dismiss(); // progressDialog.setCancelable(true); } } }

您的代码应该像上面那样改变。你需要考虑的事情

连接应该在doInBackground()内编码
如果你想得到doInBackground()的结果，你必须把它带入onPostExecute()
这意味着您必须在doInBackground()中返回一个String值，其中AsyncTask类的第三个参数也应该是String（这不是Wayne的答案）

在你的代码中，你正在调用除了“else”部分之外我们看不到的InputStream。如果您只使用InputStream，请确保代码始终到达else部分。
另一答案您使用了错误的AsyncTask方法来放置与网络相关的代码。请把它移到doInBackground，因为onPreExecute发生在主线上。所以，发生了异常。详情是here。
另一答案【为什么我用AsyncTask获取android.os.NetworkOnMainThreadException（）】将所有网络请求代码放在doInBackground中。 onPreExecute和onPostExecute将在UI线程（主要的thead）上运行，因此如果您在这两种方法上请求网络，您将获得一个例外。

public class Background_confirmation extends AsyncTask< Void, Integer, Void> { @Override protected void onPreExecute() { progressDialog = ProgressDialog.show(Confirmation.this, "Please wait...", "Retrieving data ...", true); }@Override protected Void doInBackground(Void... params) { // TODO Auto-generated method stubtry { HttpClient httpclient = new DefaultHttpClient(); HttpPost httppost = new HttpPost( "http://68.121.167.160/sip_chat_api/create_account.php?useralias=" + useralias + "& cntname=" + cntcode + ""); HttpResponse response = httpclient.execute(httppost); HttpEntity entity = response.getEntity(); is = entity.getContent(); } catch (Exception e) { e.printStackTrace(); } if (backgroung_flag == 1) {} else { if (is != null) { try { BufferedReader reader = new BufferedReader( new InputStreamReader(is, "UTF-8")); StringBuilder sb = new StringBuilder(); String line = null; while ((line = reader.readLine()) != null) { sb.append(line + " "); } is.close(); result = sb.toString(); } catch (Exception e) { Log.e("log_tag", "Error converting result " + e.toString()); } }} }@Override protected void onPostExecute(String result) { // TODO Auto-generated method stub if (progressDialog.isShowing()) { progressDialog.dismiss(); // progressDialog.setCancelable(true); }}}