Apps TodoList application help

import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;

public class DbHelper extends SQLiteOpenHelper {
	
	//The name of the database.
	public static final String DATABASE_NAME = "tobuydatabase";
	//The version of the database.
	public static final int DATABASE_VERSION = 1;
	
	// Database creation sql statement
	private static final String DATABASE_CREATE = "create table tobuy (_id integer primary key autoincrement, "
					+ "title text not null, url text not null, price text not null);";
	
	/**
	 * Constructor of this class.
	 */
	public DbHelper(Context context){
		super(context, DATABASE_NAME, null, DATABASE_VERSION);
	}

	//This method is called during the creation of the database
	@Override
	public void onCreate(SQLiteDatabase db) {
		db.execSQL(DATABASE_CREATE);
	}

	//This method is called during an upgrade of the database e.g. if you increase
	// the database version
	@Override
	public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
		db.execSQL("DROP TABLE IF EXISTS tobuy");
		onCreate(db);
	}

}

import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;

public class DbAdapter {
	
	/**
	 * Database fields
	 */
	public static final String KEY_ROWID = "_id";
	public static final String KEY_TITLE = "title";
	public static final String KEY_URL = "url";
	public static final String KEY_PRICE = "price";
	
	/**
	 * Name of the table
	 */
	private static final String DATABASE_TABLE = "tobuy";
	
	private SQLiteDatabase database;
	private DbHelper dbHelper;
	private Context context;
	
	/**
	 * Constructor of this class.
	 * @param context
	 */
	public DbAdapter(Context context){
		this.context = context;
	}
	
	/**
	 * This method get a connection to the database to query it.
	 * @return the same DbAdatper but with a connection to the database.
	 * @throws SQLException
	 */
	public DbAdapter open() throws SQLException{
		dbHelper = new DbHelper(context);
		database = dbHelper.getWritableDatabase();
		return this;
	}
	
	/**
	 * This method close the database.
	 */
	public void close(){
		dbHelper.close();
	}
	
	/**
	 * Create a new tobuy if the tobuy is successfully created return the new
	 * rowId for that note, otherwise return a -1 to indicate failure.
	 */
	public long createTobuy(String title,String url, String price){
		ContentValues initialValues = createContentValues(title,url,price);
		return database.insert(DATABASE_TABLE, null, initialValues);
	}
	
	/**
	 * Update the tobuy.	
	 */
	public boolean updateTobuy(long rowId, String title, String url,
			String price){
		ContentValues updateValues = createContentValues(title,url,price);
		return database.update(DATABASE_TABLE, updateValues, KEY_ROWID + "=" + rowId, null) > 0;
	}
	
	/**
	 * Delets tobuy
	 */
	public boolean deleteTobuy(long rowId){
		return database.delete(DATABASE_TABLE,KEY_ROWID + "=" + rowId,null) > 0;
	}
		
	/**
	 * Return a Cursor over the list of all tobuy in the database
	 * 
	 * @return Cursor over all notes
	 */
	public Cursor fetchAllTobuy(){
		return database.query(DATABASE_TABLE, new String[]{KEY_ROWID,KEY_TITLE,KEY_URL,KEY_PRICE}, null, null, null, null, null);
	}
	
	/**
	 * Return a Cursor positioned at the defined tobuy
	 */
	public Cursor fetchToBuy(long rowId) throws SQLException{
		Cursor mCursor = database.query(true, DATABASE_TABLE, new String[]{KEY_ROWID,KEY_TITLE,KEY_URL,KEY_PRICE}, 
				KEY_ROWID + "=" + rowId, null, null, null, null, null);
		if (mCursor != null){
			mCursor.moveToFirst();
		}
		return mCursor;
	}
	
	/**
	 * This method return a contentvalues with all the 3 information
	 * that we need to insert in the database.
	 * 
	 * @param title title of the toBuy.
	 * @param url url of the toBuy (If It's an online object).
	 * @param price price of the toBuy.
	 * @return ContentValues with all the three parameters of the method.
	 */
	private ContentValues createContentValues(String title, String url,
			String price) {
		ContentValues values = new ContentValues();
		values.put(KEY_TITLE,title);
		values.put(KEY_URL,url);
		values.put(KEY_PRICE,price);
		return values;
	}

import android.app.ListActivity;
import android.content.Intent;
import android.database.Cursor;
import android.os.Bundle;
import android.view.ContextMenu;
import android.view.ContextMenu.ContextMenuInfo;
import android.view.Menu;
import android.view.MenuInflater;
import android.view.MenuItem;
import android.view.View;
import android.widget.AdapterView.AdapterContextMenuInfo;
import android.widget.SimpleCursorAdapter;



public class ToBuyListActivity extends ListActivity{
	
	private DbAdapter dbAdapter;
	private Cursor cursor;
	private static final int DELETE_ID = Menu.FIRST + 1;
	
	/** Called when the activity is first created. */
	@Override
	public void onCreate(Bundle savedInstanceState){
		super.onCreate(savedInstanceState);
		setContentView(R.layout.tobuy_list);
		
		//this.getListView().setDividerHeight(2);
		dbAdapter = new DbAdapter(this);
		dbAdapter.open();
	    fillData();
	}

	private void fillData(){
		
		cursor = dbAdapter.fetchAllTobuy();
		startManagingCursor(cursor);
		
		String[] from = new String[] {DbAdapter.KEY_TITLE};
		int[] to = new int[] {R.id.titleTextView};
		
		SimpleCursorAdapter notes = new SimpleCursorAdapter(this,R.layout.tobuy_row,cursor,from,to);
		
		setListAdapter(notes);
		
	}
	
	@Override
 	protected void onDestroy() {
 		super.onDestroy();
 		if (dbAdapter != null) {
 			dbAdapter.close();
 		}
 	}
    
	
}