在Android中实现登录功能

Question

我需要在我的Android应用程序中实现登录功能，我是Android编程中的新手

我有登录活动，这也是我的主要活动，所以我读到了AsyncTask，用于在主要活动中实现HTTP请求，我按照自己的方式进行操作。

我的问题是我的代码似乎是正确的但它不是:)并且在DDMS中抛出我和错误

这是我的登录活动代码：

package ir.alldigitall.pos;

import android.app.Activity;
import android.content.Intent;
import android.content.SharedPreferences;
import android.os.Bundle;
import android.os.StrictMode;
import android.view.View;
import android.widget.CheckBox;
import android.widget.EditText;
import android.widget.Toast;


import android.os.AsyncTask;
public class Login extends Activity
{
public  String auth="";

protected void onCreate(Bundle paramBundle)
{
SharedPreferences userDetails = getSharedPreferences("userdetails", 0);
String user = userDetails.getString("username", "");
String pass = userDetails.getString("password", "");
super.onCreate(paramBundle);
if ((user == "") && (pass == ""))
{
setContentView(R.layout.activity_login);
return;
}
startActivity(new Intent("ir.alldigitall.pos.CreateInvoice"));
}

private class ReadJSON extends AsyncTask<String,Void,String>
{
protected String doInBackground(String...Detail)
{
Adapter adb=new Adapter();
String result=adb.login(Detail[0], Detail[1]);
return result;
}
protected void onPostExecute(String result)
{
auth=result;
}

}
public void onClickLoginBtn(View paramView)
{
 StrictMode.ThreadPolicy policy = new  
 StrictMode.ThreadPolicy.Builder().permitAll().build();   
 StrictMode.setThreadPolicy(policy); 

 SharedPreferences userDetails = getSharedPreferences("userdetails", 0);

 CheckBox ch_remember = (CheckBox)findViewById(R.id.ch_remember);
 EditText txt_StaffID = (EditText)findViewById(R.id.txt_StaffID);
 EditText txt_password = (EditText)findViewById(R.id.txt_password);


 String[]  ar=new String[2];
 ar[0]=txt_StaffID.getText().toString();
 ar[1]=txt_password.getText().toString();

new ReadJSON().execute(ar);

 if (ch_remember.isChecked())
 {
   SharedPreferences.Editor detailEditor = userDetails.edit();
   detailEditor.clear();
   detailEditor.putString("username", txt_StaffID.getText().toString().trim());
   detailEditor.putString("password", txt_password.getText().toString().trim());
   detailEditor.commit();
   Toast.makeText(this, auth.toString(), Toast.LENGTH_LONG).show();
   startActivity(new Intent("ir.alldigitall.pos.CreateInvoice"));
        }
 else
 {
 Toast.makeText(this, auth.toString(), Toast.LENGTH_LONG).show();
 startActivity(new Intent("ir.alldigitall.pos.CreateInvoice"));
 }

 }
 }

我的JSON Adapbter是：

package ir.alldigitall.pos;

import java.io.BufferedReader;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.io.IOException;

import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.NameValuePair;
import org.apache.http.client.HttpClient;
import org.apache.http.client.entity.UrlEncodedFormEntity;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.impl.client.DefaultHttpClient;
import org.apache.http.message.BasicNameValuePair;
import org.json.JSONException;
import org.json.JSONObject;

import android.util.Log;

public class Adapter {
public String login(String uname,String password)
{
     InputStream is = null;
     String result = "";
     JSONObject JObject=null;
     ArrayList<NameValuePair> nameValuePairs = new ArrayList<NameValuePair>();

     try 
     {  
           HttpClient httpclient = new DefaultHttpClient();

               HttpPost httppost = newHttpPost("http://10.0.2.2/pos/pos.asmx?op=Authenticate");
           nameValuePairs.add(new BasicNameValuePair("StaffID", uname));
           nameValuePairs.add(new BasicNameValuePair("Password", password));
           httppost.setEntity(new UrlEncodedFormEntity(nameValuePairs));
           HttpResponse response = httpclient.execute(httppost);
           HttpEntity entity = response.getEntity();

           is = entity.getContent();

      }

      catch (IOException e)
      {
       Log.e("log_tag", "Error in http connection " + e.getLocalizedMessage());
      }
  // convert response to string
      try 
      {
           BufferedReader reader = new BufferedReader(new InputStreamReader( is, "utf-8"), 8);
           StringBuilder sb = new StringBuilder();
           String line = null;

       while ((line = reader.readLine()) != null) 
       {
           sb.append(line + "\n");
       }

        is.close();
        result = sb.toString();

       Log.v("log","Result :"+result);

       //Convert String to JSON
       try{

           JObject = new JSONObject(result);


           }catch(JSONException e){

           Log.e("log_tag", "Error parsing data "+e.getLocalizedMessage());

           }
  } 
  catch (Exception e)
  {
   Log.v("log", "Error converting result " + e.getLocalizedMessage());
  }


    return JObject.toString();
}

 }

最后我的错误日志：

http://pastebin.com/MwG88h5Z