Getting data from the server and loading new screen using Android

Question

I am using following code to get data from the Server and if the value from server is GEEK then it will load to next class, but new view is not loading. Can you say what is the problem?

    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        login = (Button) findViewById(R.id.login);
        username = (EditText) findViewById(R.id.username);
        password = (EditText) findViewById(R.id.password);

        login.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View v) {
String Re;
                String   mUsername = username.getText().toString();
                String  mPassword = password.getText().toString();

                Re=tryLogin(mUsername, mPassword);

                if(Re=="GEEK")
                {
                    Intent i = new Intent();
                    i.setClassName(v.getContext(),"com.httplogin.MainScreen");
                    startActivity(i);

                }
            }
        });
    }

    protected String tryLogin(String mUsername, String mPassword)
    {           
        HttpURLConnection connection;
       OutputStreamWriter request = null;

            URL url = null;   
            String response = null;         
            String parameters = "username="+mUsername+"&password="+mPassword;   

            try
            {
                url = new URL("http://serverspace/script.php");
                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(parameters);
                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();

                isr.close();
                reader.close();


            }
            catch(IOException e)
            {
                Toast.makeText(this,e.toString(),0).show();
            }
            return response;
    }
}

Answer 1

Refer this code.............., Use trim function because it eliminates the space in a String..

public class HttpLogin extends Activity {
    /** Called when the activity is first created. */
    private Button login;
    private EditText username, password;

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

        login = (Button) findViewById(R.id.login);
        username = (EditText) findViewById(R.id.username);
        password = (EditText) findViewById(R.id.password);

        login.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View v) {
             String Re;
                String   mUsername = username.getText().toString();
                String  mPassword = password.getText().toString();

                Re=tryLogin(mUsername, mPassword);
                Log.d(" Check ","Here");
                Log.d("Re",Re);
                String temp_check=Re.trim();
                if(temp_check.equals("GEEK"))
                {
                    Intent i = new Intent();
                    i.setClassName(v.getContext(),"com.httplogin.MainScreen");
                    startActivity(i);

                }
                else
                {
                 //Toast.makeText(HttpLogin.this,"MAX Returned",0).show();
                 displayAlert(Re);
//                  Intent i = new Intent();
//                     i.setClassName(v.getContext(),"com.san.MainScreen");
//                     startActivity(i);
                }
            }
        });
    }

    protected String tryLogin(String mUsername, String mPassword)
    {           
      Log.d(" TryLoginCheck ","Here");
        HttpURLConnection connection;
       OutputStreamWriter request = null;

            URL url = null;   
            String response = null;   
            String temp=null;
            String parameters = "username="+mUsername+"&password="+mPassword;   
            System.out.println("UserName"+mUsername+"\n"+"password"+mPassword);
            Log.d("Parameters",parameters);
            try
            {

                url = new URL("http://serverspace/script.php");
                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(parameters);
                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");
                }
                temp=sb.toString();
                Log.d("Temp",temp);
                // Response from server after login process will be stored in response variable.                
                response = sb.toString();
                Log.d("Response",response);
               Log.d("Sb Value",sb.toString());
                isr.close();
                reader.close();


            }
            catch(IOException e)
            {
                Toast.makeText(this,e.toString(),0).show();
            }
           // Log.d("Response",response);
            return response;
    }
    public  void displayAlert(String Re)
    {
     new AlertDialog.Builder(this).setMessage(Re)
        .setTitle("Returned Value")  
        .setCancelable(true)  
        .setNeutralButton(android.R.string.ok, new DialogInterface.OnClickListener() {  
           public void onClick(DialogInterface dialog, int whichButton){
            finish();
           }  
           })  
        .show(); 
    }
}

Answer 2

Is it Case Sensitive? You should be using .equalsIgnoreCase() when comparing strings in which the case does not matter and .equals() when it does. Also have you stepped through this and debugged to make sure tryLogin(mUsername, mPassword) was returning the expected value?

Answer 3

One of the important things to note about your code is that you should never run long-time operations, such as remote server access (tryLogin() call in your case) from the UI thread. This kind of programming will lead to ANR in your application. For more details about this topic, read this article

Briefly, instead of call to tryLogin from onCreate, create async task

new LoginTask().execute(mUsername, mPassword);

Login task should be defined like this:

private class LoginTask extends AsyncTask<string, void,="" String=""> {
     protected String doInBackground(String... login) {
         return tryLogin((login[0],login[1]);
     }

     protected void onPostExecute(String result) {
        if(result.equalsIgnoreCase("GEEK"))
        {
            Intent i = new Intent();
            i.setClassName(v.getContext(),"com.httplogin.MainScreen");
            startActivity(i);
        }
     }
 }