10

当我在 AsynkTask 中编写网络操作代码时，我得到了 android.os.NetworkOnMainThreadException。抛出这个异常还有其他原因吗？

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 + "\n");
                        }
                        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 stub

            return 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() 中调用这个类

new Background_confirmation().execute();

但它总是进入 Catch 块并给我这个例外LogCat
任何建议和想法都会受到赞赏。
谢谢

4

3 回答 3

5

您使用了错误的 AsyncTask 方法来放置您的网络相关代码。请把它移到doInBackground，因为onPreExecute发生在主线程上。所以，异常发生了。详情在这里。

于 2012-08-28T06:23:51.960 回答
4 
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 + "\n");
                        }
                        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);
            }
        }
    }

你的代码应该像上面一样改变。你必须考虑的事情

  • 连接应该在里面编码doInBackground()
  • 如果你想得到 的结果doInBackground()，你必须接受它onPostExecute()
  • 这意味着您必须返回一个字符串值，doInBackground()其中您的类的第三个参数也AsyncTask应该是字符串（这不在韦恩的回答中）

在您的代码中，您调用的 aInputStream除了在“else”部分中我们看不到。如果您只使用 that InputStream，请确保代码始终到达 else 部分。

于 2012-08-28T06:42:58.790 回答
3

将所有网络请求代码放入doInBackground. onPreExecute并将onPostExecute在 UI 线程（main thead）上运行，因此如果您在这两种方法上请求网络，您将得到一个例外。

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 stub

        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 + "\n");
                    }
                    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);
        }

    }

}
于 2012-08-28T06:34:26.173 回答