Sqlite Database

[sabbu]

i have a sqlite database i want to open and select one table from the database.and bind in combobox.but i have find error <unavailable synchroneous data>please help me i am sending the code.
////////////header///////////

#ifndef MYWIDGET_H
#define MYWIDGET_H
 
#include <QWidget>
#include<QtGui>
#include <QtSql/QSqlDatabase>
#include <QtSql/QSqlQueryModel>
#include<QtSql/QSqlTableModel>
#include<QtSql/QSqlRelationalTableModel>
#include<QtSql/QSqlRelation>
 
#include <QtCore>
 
 
namespace Ui {
    class MyWidget;
}
class QListWidget;
class QListWidgetItem;
class QComboBox;
class QSqlRelationalTableModel;
class MyWidget : public QWidget
{
    Q_OBJECT
 
public:
    explicit MyWidget(QWidget *parent = 0);
    ~MyWidget();
 
private slots:
    void itemClicked(QListWidgetItem *item);
  bool  createConnection() ;
private:
 
      QListWidget *m_myListWidget;
      QComboBox *typeComboBox;
      QComboBox *typeComboBox2;
      QLabel *nameLabel;
      QLabel *addressLabel;
      QLabel *typeLabel;
      QLineEdit *nameEdit;
      QPushButton *nextButton;
 
     QVBoxLayout* lay;
     QSizeGrip *gr ;//to resize the widget
    QScrollArea *scroll;
    QSqlDatabase  db;
    QSqlRelationalTableModel *model;
    QItemSelectionModel *selectionModel;
    QDataWidgetMapper *mapper;
int typeIndex;
};
 
#endif // MYWIDGET_H

#ifndef MYWIDGET_H
#define MYWIDGET_H

#include <QWidget>
#include<QtGui>
#include <QtSql/QSqlDatabase>
#include <QtSql/QSqlQueryModel>
#include<QtSql/QSqlTableModel>
#include<QtSql/QSqlRelationalTableModel>
#include<QtSql/QSqlRelation>

#include <QtCore>


namespace Ui {
    class MyWidget;
}
class QListWidget;
class QListWidgetItem;
class QComboBox;
class QSqlRelationalTableModel;
class MyWidget : public QWidget
{
    Q_OBJECT

public:
    explicit MyWidget(QWidget *parent = 0);
    ~MyWidget();

private slots:
    void itemClicked(QListWidgetItem *item);
  bool  createConnection() ;
private:

      QListWidget *m_myListWidget;
      QComboBox *typeComboBox;
      QComboBox *typeComboBox2;
      QLabel *nameLabel;
      QLabel *addressLabel;
      QLabel *typeLabel;
      QLineEdit *nameEdit;
      QPushButton *nextButton;

     QVBoxLayout* lay;
     QSizeGrip *gr ;//to resize the widget
    QScrollArea *scroll;
    QSqlDatabase  db;
    QSqlRelationalTableModel *model;
    QItemSelectionModel *selectionModel;
    QDataWidgetMapper *mapper;
int typeIndex;
};

#endif // MYWIDGET_H

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////////////////////.cpp////////////

#include "mywidget.h"
#include "ui_mywidget.h"
#include <QtCore>
  #include <QtSql/QSqlDatabase>
 
MyWidget::MyWidget(QWidget *parent) :
    QWidget(parent)
 
{
    m_myListWidget = new QListWidget(this);
    new QListWidgetItem(tr("From"), m_myListWidget);
 
              connect( m_myListWidget, SIGNAL(itemClicked(QListWidgetItem *)), SLOT(itemClicked (QListWidgetItem *)));
 
}
void MyWidget::itemClicked(QListWidgetItem *item)
{
          m_myListWidget->hide();
          createConnection() ;
          model = new QSqlRelationalTableModel(this);
          model->setTable("CityType");
           model->setEditStrategy(QSqlTableModel::OnManualSubmit);
          model->setRelation(typeIndex,QSqlRelation("CityType","rowid", "cityName"));
          model->select();
 
 
                  addressLabel = new QLabel(tr("City:"));
                  typeComboBox = new QComboBox();
                   typeLabel = new QLabel(tr("&Area:"));
                    typeComboBox2 = new QComboBox();
 
                    nameLabel = new QLabel(tr("&street:"));
                    nameEdit = new QLineEdit();
                    nextButton = new QPushButton(tr("&Submit"));
                    // typeComboBox->addItem("Delhi");
                     // typeComboBox->addItem("Gurgaon");
                      // typeComboBox->addItem("Noida");
                    addressLabel->setBuddy(typeComboBox);
                    typeLabel->setBuddy(typeComboBox2);
                    nameLabel->setBuddy(nameEdit);
 
                       QSqlTableModel *relModel = model->relationModel(typeIndex);
                  typeComboBox->setModel(relModel);
                 typeComboBox->setModelColumn(relModel->fieldIndex("cityName"));
                  // typeComboBox->setModelColumn("cityName") ;
 
 
 
                  QGridLayout *layout = new QGridLayout();
                   layout->addWidget(addressLabel, 0, 0, 1, 1);
                   layout->addWidget(typeComboBox, 0, 1, 1, 1);
                   layout->addWidget(typeLabel, 1, 0, 1, 1);
                   layout->addWidget(typeComboBox2, 1, 1, 1, 1);
                   layout->addWidget( nameLabel, 2, 0, 1, 1);
                   layout->addWidget(nameEdit, 2, 1, 1, 1);
                   layout->addWidget(nextButton, 3, 1, 1, 1);
                   setLayout(layout);
 
                         item->~QListWidgetItem();
 
 
 
 
}
  bool MyWidget::createConnection()
{
     db = QSqlDatabase::addDatabase("QSQLITE");
    //db .setDatabaseName("C:\NokiaQtSDK\project/MyWidget/CabBookingDatabase.Sqlite");
       db.setDatabaseName("CabBookingDatabase.Sqlite");
 
     if (!db.open())
      {
 
      return false;
      }
    return true;
 
 
 
}
 
 
 
MyWidget::~MyWidget()
{
 
}

#include "mywidget.h"
#include "ui_mywidget.h"
#include <QtCore>
  #include <QtSql/QSqlDatabase>

MyWidget::MyWidget(QWidget *parent) :
    QWidget(parent)

{
    m_myListWidget = new QListWidget(this);
    new QListWidgetItem(tr("From"), m_myListWidget);

              connect( m_myListWidget, SIGNAL(itemClicked(QListWidgetItem *)), SLOT(itemClicked (QListWidgetItem *)));

}
void MyWidget::itemClicked(QListWidgetItem *item)
{
          m_myListWidget->hide();
          createConnection() ;
          model = new QSqlRelationalTableModel(this);
          model->setTable("CityType");
           model->setEditStrategy(QSqlTableModel::OnManualSubmit);
          model->setRelation(typeIndex,QSqlRelation("CityType","rowid", "cityName"));
          model->select();


                  addressLabel = new QLabel(tr("City:"));
                  typeComboBox = new QComboBox();
                   typeLabel = new QLabel(tr("&Area:"));
                    typeComboBox2 = new QComboBox();

                    nameLabel = new QLabel(tr("&street:"));
                    nameEdit = new QLineEdit();
                    nextButton = new QPushButton(tr("&Submit"));
                    // typeComboBox->addItem("Delhi");
                     // typeComboBox->addItem("Gurgaon");
                      // typeComboBox->addItem("Noida");
                    addressLabel->setBuddy(typeComboBox);
                    typeLabel->setBuddy(typeComboBox2);
                    nameLabel->setBuddy(nameEdit);

                       QSqlTableModel *relModel = model->relationModel(typeIndex);
                  typeComboBox->setModel(relModel);
                 typeComboBox->setModelColumn(relModel->fieldIndex("cityName"));
                  // typeComboBox->setModelColumn("cityName") ;



                  QGridLayout *layout = new QGridLayout();
                   layout->addWidget(addressLabel, 0, 0, 1, 1);
                   layout->addWidget(typeComboBox, 0, 1, 1, 1);
                   layout->addWidget(typeLabel, 1, 0, 1, 1);
                   layout->addWidget(typeComboBox2, 1, 1, 1, 1);
                   layout->addWidget( nameLabel, 2, 0, 1, 1);
                   layout->addWidget(nameEdit, 2, 1, 1, 1);
                   layout->addWidget(nextButton, 3, 1, 1, 1);
                   setLayout(layout);

                         item->~QListWidgetItem();




}
  bool MyWidget::createConnection()
{
     db = QSqlDatabase::addDatabase("QSQLITE");
    //db .setDatabaseName("C:\NokiaQtSDK\project/MyWidget/CabBookingDatabase.Sqlite");
       db.setDatabaseName("CabBookingDatabase.Sqlite");

     if (!db.open())
      {

      return false;
      }
    return true;



}



MyWidget::~MyWidget()
{

}

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///////////.pro///////////

QT += sql