Error when start activity and upload Database

Question

When I click a Button I starting a new activity, called Profilo.java. My code is:

package com.example.prenotazione_esame;

import android.app.Activity; import android.app.AlertDialog; import android.content.DialogInterface; import android.database.Cursor; import android.database.sqlite.SQLiteDatabase; import android.os.*; import android.view.Menu; import android.view.MenuItem; import android.widget.Button; import android.widget.EditText; import android.view.View; import android.view.View.OnClickListener; import android.widget.Toast;

public class Profilo extends Activity {
private LoginDataBase dbLogin;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    int id = getIntent().getExtras().getInt("id");
    setContentView(R.layout.profilo);
    SQLiteDatabase db = dbLogin.getWritableDatabase();
}

}

this LoginDataBase.java

public class LoginDataBase extends SQLiteOpenHelper {
    private static final String DB_NAME="Login_DB";
    private static final int DB_VERSION=1;

    public LoginDataBase(Context context){
        super(context,DB_NAME,null,DB_VERSION);
    }
    @Override 
     public void onCreate(SQLiteDatabase db) { 
        String sql="";
        sql+= "CREATE TABLE T_LOGIN (";
        sql+= " _id_LOGIN INTEGER PRIMARY KEY AUTOINCREMENT,";
        sql+= " USERNAME TEXT NOT NULL,";
        sql+= " PASSWORD TEXT NOT NULL";
        sql+=")";
        db.execSQL(sql);

        String sql2="";
        sql2+= "CREATE TABLE T_PROFILO (";
        sql2+= " _id_PROFILO INTEGER PRIMARY KEY AUTOINCREMENT,";
        sql2+= " NOME TEXT NOT NULL,";
        sql2+= " COGNOME TEXT NOT NULL,";
        sql2+= " ETA TEXT NOT NULL,";
        sql2+= " SESSO TEXT(1) NOT NULL,";
        sql2+= " CODICE_FISCALE TEXT NOT NULL,";
        sql2+= " CITTA TEXT NOT NULL,";
        sql2+= " INDIRIZZO TEXT NOT NULL,";
        sql2+= " TELEFONO TEXT NOT NULL,";
        sql2+= " _id_L INTEGER NOT NULL,";
        sql2+= " FOREIGN KEY(_id_L) REFERENCES T_LOGIN(_id_LOGIN)";
        sql2+= ")";
        db.execSQL(sql2);
     } 

     @Override 
     public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { 
        // Aggiornamento delle tabelle 
     } 
}

the problem is when I try to take my database db. My app crash. Where is the problem?

Answer 1

You need to inicializate dbLogin.

protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
int id = getIntent().getExtras().getInt("id");
setContentView(R.layout.profilo);
       ///NEW
  LoginDataBase dbLogin =  new LoginDataBase (this, "NAMEOFDATABASE", null, 1);
      ///END OF NEW
    SQLiteDatabase db = dbLogin.getWritableDatabase();

}

} 

You class LoginDataBase must have a constructor similar than this:

public class LoginDataBase extends SQLiteOpenHelper {
private static final String DB_NAME="Login_DB";
private static final int DB_VERSION=1;


public LoginDataBase (Context contexto, String name,
                           CursorFactory factory, int version) {
    super(contexto, name, factory, version);
}

Or you can also change this and continue with your constructor:

 ///NEW
  LoginDataBase dbLogin =  new LoginDataBase (this);
  ///END OF NEW