App crashes at startActivity(intent)

Question

this app crashes when i push over botonRegistro. The intent is created but i think is saved as null and i don´t know why. This is the code:

import com.example.pestanasholacampus.R;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.app.Activity;
import android.content.Intent;

  
public class InitActivity extends Activity {

protected EditText usuarioIntroducido;
protected EditText pwdIntroducida;
protected Button botonEntrada;
protected Button botonRegistro;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_acceso);
    System.out.println("Contenido enlazado");

    // obtenemos los recursos de la clase R para la activity_main
    usuarioIntroducido = (EditText) findViewById(R.id.usuarioIntroducido);
    pwdIntroducida = (EditText) findViewById(R.id.contrasenaIntroducida);
    botonEntrada = (Button) findViewById(R.id.botonEntrar);
    botonRegistro = (Button) findViewById(R.id.BotonRegistro);
    System.out.println("Variables asociadas");

    botonRegistro.setOnClickListener(new OnClickListener() {

        @Override
        public void onClick(View v) {
            Intent intentRegistro = new Intent(getBaseContext(), // I think intentRegistro is saved as null
                    RegistroActivity.class);
            startActivity(intentRegistro); //NullpointerException at this point
        }
    });
    botonEntrada.setOnClickListener(new OnClickListener() {

        @Override
        public void onClick(View v) {
            /*
             * String usuario = usuarioIntroducido.getText().toString();
             * String clave = pwdIntroducida.getText().toString();
             * compruebaUsuario(v);
             */
            Intent intentEntrar = new Intent(getBaseContext(),
                    MainActivity.class);
            System.out.println("Boton entrar pulsado.");
            startActivity(intentEntrar);
        }
    });

    // Enlace al activity de registro mediante el boton

}

public void compruebaUsuario(View view) {// La entrada es desde la view que
                                            // se ha llamado (los botones
                                            // son views)
    Intent intent = new Intent(getBaseContext(), MainActivity.class);
    intent.putExtra("user", usuarioIntroducido.getText());
    intent.putExtra("pwd", pwdIntroducida.getText());
    // El start Activity iría despues de comprobar el usuario con la BDD.
    startActivity(intent);
}

}

The debugger error is: Unable to start activity ComponentInfo {com.example.pestanasholacampus/com.example.pestanasholacampus.RegistroActivity}: java.lang.NullPointerException

Edit:This is my RegistroActivity

package com.example.pestanasholacampus;

import com.example.pestanasholacampus.GestionRegistros;
import com.example.pestanasholacampus.R;
import com.example.pestanasholacampus.Usuario;
import com.example.pestanasholacampus.R.id;
import com.example.pestanasholacampus.R.layout;
import com.example.pestanasholacampus.R.menu;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;

public class RegistroActivity extends Activity{

private EditText nombre= (EditText)findViewById(R.id.pideNombre);
private EditText apellido1= (EditText)findViewById(R.id.pideAp1);
private EditText apellido2= (EditText)findViewById(R.id.pideAp2);
private EditText universidad= (EditText)findViewById(R.id.pideCampus);
private EditText telefono= (EditText)findViewById(R.id.pideTelefono);
private EditText mail= (EditText)findViewById(R.id.pideEmail);
private EditText clave= (EditText)findViewById(R.id.pideClave); 

private Button botonReg= (Button)findViewById(R.id.BotonRegistro);

protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.actividad_registro);
    botonReg.setOnClickListener(new View.OnClickListener() {
        Usuario usuario= new Usuario();
        @Override
        public void onClick(View v) {
            //Obtenemos los datos introducidos y los almacenamos en la clase usuario
            usuario.setNombre(nombre.getText().toString());
            usuario.setApellido1(apellido1.getText().toString());
            usuario.setApellido2(apellido2.getText().toString());
            usuario.setCampus(universidad.getText().toString());
            usuario.setClave(clave.getText().toString());
            usuario.setTelefono(telefono.getText().toString());
            usuario.setEmail(mail.getText().toString());
            
            GestionRegistros gestor= new GestionRegistros();
            
            
        }
    });
    
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.main, menu);
    
    
    return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    // Handle action bar item clicks here. The action bar will
    // automatically handle clicks on the Home/Up button, so long
    // as you specify a parent activity in AndroidManifest.xml.
    int id = item.getItemId();
    if (id == R.id.action_settings) {
        return true;
    }
    return super.onOptionsItemSelected(item);
}

}

Thanks.

Answer 1

try this

 Intent intentEntrar = new Intent(getApplicationContext(),MainActivity.class);          
 startActivity(intentEntrar);

also make sure that you have declared your MainActivity in manifest.xml

Answer 2

Move all your findViewById s after setContentView in onCreate . They are giving you Null Pointer Exception.

setContentView(R.layout.actividad_registro);
nombre= (EditText)findViewById(R.id.pideNombre);
apellido1= (EditText)findViewById(R.id.pideAp1);
apellido2= (EditText)findViewById(R.id.pideAp2);
universidad= (EditText)findViewById(R.id.pideCampus);
telefono= (EditText)findViewById(R.id.pideTelefono);
mail= (EditText)findViewById(R.id.pideEmail);
clave= (EditText)findViewById(R.id.pideClave); 

botonReg= (Button)findViewById(R.id.BotonRegistro);

Your activity layout is created after call to setContentView, so you must initialize your layout views after that call.

Hope this helps.

Answer 3

private Button botonReg= (Button)findViewById(R.id.BotonRegistro);

You're calling findViewById() too early, at member variable initialization phase.

Move all the initializations involving findViewById() to onCreate() after setContentView() .

Answer 4

Nice explanation.. I have faced the same problem, just want to add that initialization of components have to be after oncreate() -> setContentView() in source activity as well as in target activity also.

Otherwise the app will keep on crashing.

The problem here was NullPointerException .