使用AsyncTask的NullPointerException和IOException

Question

我尝试对发送用户名和密码以及Google地图中的某些圈子的服务器发送应该发布的内容。目前我收到了java.lang.NullPointerException。调试后我发现＆＃34; response.getEntity（）;＆＃34;返回null。此外，我得到一个IOException（来自具有＆＃34;客户端＆＃34;标记logcat）的catch。根据我的理解，我的实施应该是正确的，但是我没有注意到一个问题。任何想法是什么导致了这一点 logcat的：

07-29 14:23:30.253: E/AndroidRuntime(16810): FATAL EXCEPTION: AsyncTask #1
07-29 14:23:30.253: E/AndroidRuntime(16810): Process: com.example.maptest, PID: 16810
07-29 14:23:30.253: E/AndroidRuntime(16810): java.lang.RuntimeException: An error     occured while executing doInBackground()
07-29 14:23:30.253: E/AndroidRuntime(16810):    at android.os.AsyncTask$3.done(AsyncTask.java:300)
07-29 14:23:30.253: E/AndroidRuntime(16810):    at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:355)
07-29 14:23:30.253: E/AndroidRuntime(16810):    at java.util.concurrent.FutureTask.setException(FutureTask.java:222)
07-29 14:23:30.253: E/AndroidRuntime(16810):    at java.util.concurrent.FutureTask.run(FutureTask.java:242)
07-29 14:23:30.253: E/AndroidRuntime(16810):    at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:231)
07-29 14:23:30.253: E/AndroidRuntime(16810):    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1112)
07-29 14:23:30.253: E/AndroidRuntime(16810):    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587)
07-29 14:23:30.253: E/AndroidRuntime(16810):    at java.lang.Thread.run(Thread.java:841)
07-29 14:23:30.253: E/AndroidRuntime(16810): Caused by: java.lang.NullPointerException
07-29 14:23:30.253: E/AndroidRuntime(16810):    at com.example.maptest.RegisterDialog$1$1SendSaveRequest.sendMessage(RegisterDialog.java:124)
07-29 14:23:30.253: E/AndroidRuntime(16810):    at com.example.maptest.RegisterDialog$1$1SendSaveRequest.doInBackground(RegisterDialog.java:142)
07-29 14:23:30.253: E/AndroidRuntime(16810):    at  com.example.maptest.RegisterDialog$1$1SendSaveRequest.doInBackground(RegisterDialog.java:1)
07-29 14:23:30.253: E/AndroidRuntime(16810):    at android.os.AsyncTask$2.call(AsyncTask.java:288)
07-29 14:23:30.253: E/AndroidRuntime(16810):    at java.util.concurrent.FutureTask.run(FutureTask.java:237)
07-29 14:23:30.253: E/AndroidRuntime(16810):    ... 4 more

我的代码：

saveCircles.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View v) {

            class SendSaveRequest extends AsyncTask<String, Void, String> {

                // private Gson gson = new GsonBuilder().create();
                // String data = gson.toJson(message);

                private String sendMessage(String message, String address) {
                    String url = "http://192.168.87.108:8080/MSS/"
                            + address;

                    HttpPost post = new HttpPost(url);

                    List<NameValuePair> nameValuePairs = new ArrayList<NameValuePair>(
                            1);
                    nameValuePairs.add(new BasicNameValuePair("report",
                            message));

                    try {
                        post.setEntity(new UrlEncodedFormEntity(
                                nameValuePairs));
                    } catch (UnsupportedEncodingException e) {                  
                        Log.i("client", "Your url encoding is shiat fail");
                    }

                    HttpClient client = new DefaultHttpClient();
                    HttpResponse response = null;
                    try {
                        Log.i("client", "Trying to execute");
                        response = client.execute(post);
                        Log.i("client", "Execution success");                           
                    } catch (ClientProtocolException e) {
                        Log.i("client", "Problems with execute post, ClientProtocolException");
                        e.printStackTrace();
                    } catch (IOException e) {
                        Log.i("client", "Problems with execute post, IOException");
                        e.printStackTrace();
                    }

                    HttpEntity entity = response.getEntity();

                    String responseText = "";
                    try {
                        responseText = EntityUtils.toString(entity);
                    } catch (ParseException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                    } catch (IOException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                    }
                    return responseText;

                }

                @Override
                protected String doInBackground(String... params) {
                    return sendMessage(params[0], params[1]);
                }

                @Override
                protected void onPostExecute(String result) {
                    Toast.makeText(mainActivityContext, result,
                            Toast.LENGTH_LONG).show();
                }

            }

            String msg = gson.toJson(mainActivityContext
                    .generateSavePayload(
                            mainActivityContext.circlesToArea(),
                            mainActivityContext.userId,
                            mainActivityContext.userPassword));

            new SendSaveRequest().execute(msg, "save");
        }
    });