android-asyncTask保持循环

Question

我在android开发方面有点新，我试图为app做一个登录过程，我已经在我的本地主机上的php脚本上用http post方法成功完成了这个过程，但为了让我的登录过程更好我决定使用progressdialog显示身份验证过程何时运行但进度保持循环。以下是我的代码：

LoginActivity.java - 登录按钮：

opt = new HttpRequest();
    btnLogin = (Button)findViewById(R.id.btnLogin);
    btnLogin.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View v) {
            // TODO Auto-generated method stub                                                          

            v.setEnabled(false);
            AsyncTask<Void, Void, Void> task = new AsyncTask<Void, Void, Void>() {
                private boolean authResult = false;

                @Override
                protected void onPreExecute() {
                    pd = new ProgressDialog(context);
                    pd.setTitle("Processing...");
                    pd.setMessage("Please wait.");
                    pd.setCancelable(false);
                    pd.setIndeterminate(true);
                    pd.show();                                              
                }

                @Override
                protected Void doInBackground(Void... arg0) {
                    try {
                        //Do something...
                        if(opt.loginAuth(txtUsername.getText().toString(), txtPassword.getText().toString())){                  
                            Log.i(Data.tagInfo,"Redirecting to mainpage");
                            opt.showToast(LoginActivity.this,"Login Successful");
                            startActivity(new Intent("com.example.MainActivity"));

                        }
                        else{                   
                            opt.showToast(LoginActivity.this,"Login Fail");
                            Log.i(Data.tagError,"Login Fail");

                        }                                                           

                    } catch (Exception e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                        return null;
                    }
                    return null;
                }

                @Override
                protected void onPostExecute(Void result) {

                    if (pd!=null) {
                        pd.dismiss();
                        btnLogin.setEnabled(true);                          
                    }

                }

            };
            task.execute((Void[])null);     

        }
    });

HttpRequest.java：

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.concurrent.ExecutionException;

import org.json.JSONArray;

import android.os.AsyncTask;
import android.util.Log;


public class HttpRequest extends Operations {


public boolean loginAuth(String user , String pass){
    //Log.i("Info",user+"|"+pass);                             
     String     folder      =   "mobileapp",
                script      =   "/loginAuth_m-script.php",
                fullpath    =   folder+script,
                parameter   =   "username="+user+"&password="+pass,
                result      =   "";

    try {
        JSONArray jArray = convertJSON(new SendRequest().execute(fullpath,parameter).get());
        result = getSpecificJSONdata(jArray,"result");
        Log.i(Data.tagInfo,"Login result:"+result);
            if(result.equals(Data.success)){
                Log.i(Data.tagInfo,"loginAuth() return true");
                return true;
            }
            else{
                Log.i(Data.tagInfo,"loginAuth() return false");
                return false;
            }

    } catch (Exception e) {
        // TODO Auto-generated catch block
        Log.i(Data.tagError,"Error:"+e.toString());
        return false;
    }                                                                   
}

private class SendRequest extends AsyncTask<String, Void, String>{

    @Override
    protected String doInBackground(String... arg) {
        // TODO Auto-generated method stub
            HttpURLConnection connection;
            OutputStreamWriter request = null;
            URL url = null;   
            String response = null;         


                try
                {
                    url = new URL("http://"+Data.host+"/"+arg[0]);
                    connection = (HttpURLConnection) url.openConnection();
                    connection.setDoOutput(true);
                    connection.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");
                    connection.setRequestMethod("POST");    

                        request = new OutputStreamWriter(connection.getOutputStream());
                        request.write(arg[1]);
                        request.flush();
                        request.close();            


                            String line = "";               
                            InputStreamReader isr = new InputStreamReader(connection.getInputStream());
                            BufferedReader reader = new BufferedReader(isr);
                            StringBuilder sb = new StringBuilder();
                            while ((line = reader.readLine()) != null)
                            {
                                sb.append(line + "\n");
                            }
                            // Response from server after login process will be stored in response variable.                
                            response = sb.toString();
                            // You can perform UI operations here

                    Log.i("Info","Server Response:"+response);
                    isr.close();
                    reader.close();
                    return response;
                }
                catch(IOException e)
                {
                    Log.i("InfoError",e.toString());
                    return ""; 
                    // Error
                }


    }           
}



}

非常感谢^^