Android Application- Login

[D. Capri Michael]

Hi there I'm pretty new to android!
I'm trying to develop an android application which requires login which will link/check with the server/website.
Any suggestion on how can i possibly do it?

[Tim Moores]

What do you have so far, and where are you stuck making progress? Communication with the server can be handled by the HttpClient library that is part of the Android API. You should use HTTPS, or encrypt or hash the password before sending it to the server, so that it's not sent in cleartext over the wires.

[D. Capri Michael]

Oh mainly i just designed the UI. I m stuck at how/which to use for the communication with the server as i did some research over the get/post http method and also json but still not quite sure about it. @@

[Prabu Dhanapal]

Hi,

I found a really useful blog for this. It has a sample login android application which sends the user name and the password to a remote server to validate. the server is a simple servlet application. It validates and sends the response back to android app.. It looks really simple and the below page contains complete code as well... Please go through.. Hope this would be helpful...

http://androidtechstuffs.blogspot.com/2013/01/login-application-for-android.html

[Steve Luke]

Hi Prabu, the code there leaves a lot to be desired. First, as Tim Moores said, you should not be sending the password out in the free/open like you are. You should be hashing or using HTTPS.

Second, in your OnClickListener you have code which starts a new Thread and uses that Thread to post the login to the server and wait for the response. You then, outside the Thread, immediately get the response to do something with. This is not good. It is true that the GUI Thread should not do long running processes, and that you can't update the user interface in your background Thread - but you never wait for the process to finish before trying to use the response. Either the process is fast and you don't need the Thread, or it is not and you can not rely on it being done when you try to use the response.

A better approach to use the Android AsyncTask. It is better suited to do just this sort of thing.

Finally, I think you have too much code in your OnClickListener, embedding it in the GUI code. You should try to move as much of it as you can out. For example, you have the SimpleHttpClient class - why not make a String loginToServer(String userName, String password) method which does the calls for getting the URL, submitting the post, and waiting for the response, then returns the response. You have that layer so you should use it to abstract out the commands and make them as simple as possible - and you should always strive to keep as much work as possible out of your display code.

For the reference of others, here is the code I am discussing:

/**
 * 
 */
package com.example.firstapp.clientside;

/**
 * @author Prabu
 *
 */
import java.util.ArrayList;

import org.apache.http.NameValuePair;
import org.apache.http.message.BasicNameValuePair;

import com.example.firstapp.R;

import android.annotation.SuppressLint;
import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;

@SuppressLint("NewApi")
public class LoginLayout extends Activity {
 EditText un, pw;
 TextView error;
 Button ok;
 private String resp;
 private String errorMsg;

  /** Called when the activity is first created. */
 @Override
 public void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.activity_main);
  un = (EditText) findViewById(R.id.et_un);
  pw = (EditText) findViewById(R.id.et_pw);
  ok = (Button) findViewById(R.id.btn_login);
  error = (TextView) findViewById(R.id.tv_error);

   ok.setOnClickListener(new View.OnClickListener() {

    @Override
   public void onClick(View v) {
    /** According with the new StrictGuard policy,  running long 
        tasks on the Main UI thread is not possible
     So creating new thread to create and execute http operations */
    new Thread(new Runnable() {

      @Override
     public void run() {
      ArrayList<NameValuePair> postParameters = new ArrayList<NameValuePair>();
      postParameters.add(new BasicNameValuePair("username",un.getText().toString()));
      postParameters.add(new BasicNameValuePair("password",pw.getText().toString()));

       String response = null;
      try {
       response = SimpleHttpClient.executeHttpPost("http://192.168.1.3:8084/LoginServer/login.do", 
                                                   postParameters);
       String res = response.toString();
       resp = res.replaceAll("\\s+", "");

       } catch (Exception e) {
       e.printStackTrace();
       errorMsg = e.getMessage();
      }
     }

     }).start();
    
    /** Inside the new thread we cannon update the main thread
     So updating the main thread outside the new thread */
    try {
     if (resp.equals("1")) {
      error.setText("Correct Username and Password");
     } else {
      error.setText("Sorry!! Incorrect Username or Password");
     }
     if (null != errorMsg && !errorMsg.isEmpty()) {
      error.setText(errorMsg);
     }
    } catch (Exception e) {
     error.setText(e.getMessage());
    }
   }
  });
 }
}

/**
 * 
 */
package com.example.firstapp.clientside;

/**
 * @author Prabu
 *
 */
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.URI;
import java.util.ArrayList;

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.HttpGet;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.conn.params.ConnManagerParams;
import org.apache.http.impl.client.DefaultHttpClient;
import org.apache.http.params.HttpConnectionParams;
import org.apache.http.params.HttpParams;

public class SimpleHttpClient {
 /** The time it takes for our client to timeout */
    public static final int HTTP_TIMEOUT = 30 * 1000; // milliseconds

    /** Single instance of our HttpClient */
    private static HttpClient mHttpClient;

    /**
     * Get our single instance of our HttpClient object.
     *
     * @return an HttpClient object with connection parameters set
     */
    private static HttpClient getHttpClient() {
        if (mHttpClient == null) {
            mHttpClient = new DefaultHttpClient();
            final HttpParams params = mHttpClient.getParams();
            HttpConnectionParams.setConnectionTimeout(params, HTTP_TIMEOUT);
            HttpConnectionParams.setSoTimeout(params, HTTP_TIMEOUT);
            ConnManagerParams.setTimeout(params, HTTP_TIMEOUT);
        }
        return mHttpClient;
    }

    /**
     * Performs an HTTP Post request to the specified url with the
     * specified parameters.
     *
     * @param url The web address to post the request to
     * @param postParameters The parameters to send via the request
     * @return The result of the request
     * @throws Exception
     */
    public static String executeHttpPost(String url, 
                          ArrayList<NameValuePair> postParameters) throws Exception {
        BufferedReader in = null;
        try {
            HttpClient client = getHttpClient();
            HttpPost request = new HttpPost(url);
            UrlEncodedFormEntity formEntity = new UrlEncodedFormEntity(postParameters);
            request.setEntity(formEntity);
            HttpResponse response = client.execute(request);
            in = new BufferedReader(new InputStreamReader(response.getEntity().getContent()));

            StringBuffer sb = new StringBuffer("");
            String line = "";
            String NL = System.getProperty("line.separator");
            while ((line = in.readLine()) != null) {
                sb.append(line + NL);
            }
            in.close();

            String result = sb.toString();
            return result;
        }
        finally {
            if (in != null) {
                try {
                    in.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }

    /**
     * Performs an HTTP GET request to the specified url.
     *
     * @param url The web address to post the request to
     * @return The result of the request
     * @throws Exception
     */
    public static String executeHttpGet(String url) throws Exception {
        BufferedReader in = null;
        try {
            HttpClient client = getHttpClient();
            HttpGet request = new HttpGet();
            request.setURI(new URI(url));
            HttpResponse response = client.execute(request);
            in = new BufferedReader(new InputStreamReader(response.getEntity().getContent()));

            StringBuffer sb = new StringBuffer("");
            String line = "";
            String NL = System.getProperty("line.separator");
            while ((line = in.readLine()) != null) {
                sb.append(line + NL);
            }
            in.close();

            String result = sb.toString();
            return result;
        }
        finally {
            if (in != null) {
                try {
                    in.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }
}

[Prabu Dhanapal]

Thanks for the comment Steve..

I was just thinking of communicating with the server.
The code has been updated with AsyncTask and https support. Please go through the below post. I hope this would be helpful for others.

http://androidtechstuffs.blogspot.in/2013/01/login-application-for-android-android.html





----------------------------------
Prabu

[Jason Mayer]

it looks like you're new to java, so i'd recommend using an external library such as parse for this. they handle all the security parts and it's free for up to 1 million api requests per month. I'm not new to java and I'm using it in my android app because it made getting started that much easier.
http://www.parse.com