final String username = usernameEditText.getText().toString().trim();

        final String password = passwrodEditText.getText().toString().trim();

        //Android默认模拟器外部的地址为10.0.2.2，而不是localhost和127.0.0.1

        final String serverPath = "http://10.0.2.2:8080/LoginServlet";

        if (TextUtils.isEmpty(username) || TextUtils.isEmpty(password)) {

            //给出提示：账号密码不许为空

        } else {

            new Thread(new Runnable() {

                @Override

                public void run() {

                    try {

                        //创建浏览器

                        HttpClient httpClient = new DefaultHttpClient();

                        //创建一个post请求对象

                        HttpPost httpPost = new HttpPost(serverPath);

                        //创建请求参数

                        List<NameValuePair> parameters = new ArrayList<NameValuePair>();

                        parameters.add(new BasicNameValuePair("username",username));

                        parameters.add(new BasicNameValuePair("password",password));

                        //请求参数设置到httpPost的实体里

                        httpPost.setEntity(new UrlEncodedFormEntity(parameters, "UTF-8"));

                        //浏览器提交这个请求，然后服务器返回一个HttpResponse

                        HttpResponse httpResponse = httpClient.execute(httpPost);

                        //通过返回信息获取返回的状态码

                        int statusCode = httpResponse.getStatusLine().getStatusCode();

                        if (200 == statusCode) {

                            InputStream inputStream = httpResponse.getEntity().getContent();

                            final String responseMsg = StreamTool.getString(inputStream);

                            runOnUiThread(new Runnable() {

                                @Override

                                public void run() {

                                    Toast.makeText(MainActivity.this, responseMsg, Toast.LENGTH_LONG).show();

                                }

                            });

                        } else {

                            System.out.println("statusCode = " + statusCode);

                            //连接服务器出错，错误代码为：responseCode 根据代码值告诉用户出错的原因

                            //....

                        }

                    } catch (Exception e) {

                        e.printStackTrace();

                    }

                }

            }).start();

        }

    }