Question

I have a problem with android programming. I am new in this, so don’t be judgemental.

I built a login form and when I try to login, I get in the username textbox java.lang.NullPointerException. Here is the code:

import java.util.ArrayList;
import org.apache.http.NameValuePair;
import org.apache.http.message.BasicNameValuePair;
import android.app.Activity;
import android.os.Bundle;
import android.view.View; 
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.content.Context;
import android.content.Intent;

public class Login extends Activity {
EditText un,pw;
TextView error;
Button ok;
Button reg;
private static Context context;
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_login);
    un=(EditText)findViewById(R.id.editText1);
    pw=(EditText)findViewById(R.id.editText2);
    ok=(Button)findViewById(R.id.button1);
    reg=(Button)findViewById(R.id.button2);
    ok.setOnClickListener(new View.OnClickListener() {

        public void onClick(View v) {

                            // TODO Auto-generated method stub



    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 = CustomHttpClient.executeHttpPost("<HTTP Request site>", postParameters);

    String res=response.toString();

    res= res.replaceAll("\\s+","");

    if(res.equals("1")) { 
        error.setText("Welcome to ...");
        Intent i = new Intent(context, Welcome.class);
        startActivity(i);
    }

    else

    error.setText("Sorry!! Incorrect Username or Password");

    } catch (Exception e) {

    un.setText(e.toString());

                    }
                }
            });
        }
    }

Is there any problem or a mistake that I made. Please help me. Or just give me some directions.

Thanks in advance

Answer 1

You’re getting an error because your TextView error is never initialized. Add the following line into your onCreate():

error=(TextView)findViewById(R.id.<textView_ID);