Question

I have a login.php script which will validate the username and password entered in the android. The code is below

<?php

    include('dbconnect.php'); 

    $data=file_get_contents('php://input');
    $json = json_decode($data);
    $tablename = "users";

    //username and password sent from android
    $username=$json->{'username'};
    $password=$json->{'password'};

    //protecting mysql injection
    $username = stripslashes($username);
    $password = stripslashes($password);
    $username = mysql_real_escape_string($username);
    $password = mysql_real_escape_string($password);
    $password = md5($password);

    $sql = "SELECT id FROM $tablename WHERE u_username='$username' and password='$password'"; 

    //Querying the database
    $result=mysql_query($sql);

    //If found, number of rows must be 1
    if((mysql_num_rows($result))==1){

    //creating session
    session_register("$username");
    session_register("$password");

    print "success";
    }else{
    print "Incorrect details";
    }
?>

I also have an android class from which the user will enter the username and password. The code is below.

  public class LoginActivity extends Activity {


   public static final String loginURI="http://.../login.php";

   @Override
   public void onCreate(Bundle savedInstanceState){
    super.onCreate(savedInstanceState);
    setContentView(R.layout.login);



    buttonSubmit.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {


            String userID = "";
            userID=login(editTextUsername.getText().toString(), editTextPassword.getText().toString());

            if (editTextPassword.getText().toString() != null & editTextUsername.getText().toString() != null){
                //Used to move to the Cases Activity
                Intent casesActivity = new Intent(getApplicationContext(), CasesActivity.class);
                startActivity(casesActivity);
                casesActivity.putExtra("username", userID);

            }
            else{
                //Display Toaster for error
                Toast.makeText(getApplicationContext(),"this is an error message", Toast.LENGTH_LONG).show();
            }
        }
    });


private String login(String username, String password){

    JSONObject jsonObject = new JSONObject();

    String success = "";

    HttpClient httpClient = new DefaultHttpClient();
    HttpPost httpPost = new HttpPost(loginURI);
    HttpParams httpParams = new BasicHttpParams();
    HttpConnectionParams.setConnectionTimeout(httpParams,10000);
    HttpConnectionParams.setSoTimeout(httpParams,10000);

   try {

        jsonObject.put("username", username);
        Log.i("username", jsonObject.toString());
        jsonObject.put("password", password);
        Log.i("password", jsonObject.toString());

        StringEntity stringEntity = new StringEntity(jsonObject.toString());
        stringEntity.setContentEncoding(new BasicHeader(HTTP.CONTENT_TYPE, "application/json"));
        httpPost.setEntity(stringEntity);
        HttpResponse httpResponse = httpClient.execute(httpPost);

        HttpEntity entity = httpResponse.getEntity();

        if (entity != null) {
            success = EntityUtils.toString(httpResponse.getEntity());
            Log.i("success", success);
        }

    }catch (IOException e){
        Log.e("Login_Issue", e.toString());
    }catch (JSONException e) {
        e.printStackTrace();  
    }


    return success;
  }

}

I get the following error: ERROR/AndroidRuntime(29611): FATAL EXCEPTION: main android.os.NetworkOnMainThreadException.
I understand that I need another thread and I was thinking of using AsyncTask, but I do not know where to put it in this class.

Could you also give me some advice in using JSON for sending and receiving data from android.

Thank you for your help,

Answer 1

you can change your code using AsyncTask by calling login method inside doInBackground and start next Activity on onPostExecute when login successful as :

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

String str_username=;
String str_password=;

     public LoginOperation(String str_username,String str_password){
      this.str_password=  str_password;
      this.str_username=  str_username;
     }
     @Override
      protected void onPreExecute() {

       // show progress bar here
      }
      @Override
      protected String doInBackground(String... params) {
           // call login method here
         String userID=login(str_username,str_password);
         return userID;
      }      

      @Override
      protected void onPostExecute(String result) {    
         // start next Activity here
           if(result !=null){
                Intent casesActivity = new Intent(getApplicationContext(),
                                                CasesActivity.class);
                casesActivity.putExtra("username", result);
                Your_Activiy.this.startActivity(casesActivity);

               }
      }

and start LoginOperation AsyncTask on button click as:

buttonSubmit.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {

            if (editTextPassword.getText().toString() != null 
                         & editTextUsername.getText().toString() != null){
                // start AsyncTask here
                 new LoginOperation(editTextUsername.getText().toString(),
                        editTextPassword.getText().toString()).execute("");
            }
            else{
              // your code here
            }
        }
    });

}