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C++ GUI Programming with Qt 3

Rozália Szabó NacsaEötvös Loránd University, Budapest

Faculty of Informaticsnacsa@inf.elte.hu

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The Task

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The „Tricks”

ComboBox

Modificationwith controls

Calculated field

Calculatedfield with

„info”

Read Only

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The Tables

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Database Managament using API calls

Database1

Application

API1calls

API1

Database2

Alkalmazás

API2calls

API2

Database specificfunction calls. 6

Database Management using SQL commands

Database1API1

Database2

Application

SQLcommands

API2

SQL

SQL

Database specificfunction calls Standard Query

Language

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Database Management using ODBC

Database1API1 Application

SQLcommands

ODBCfunction calls

SQL

ODBCfunctions

Database2API1

SQL

ODBCfunctions

ODBCdriver1

ODBCdriver1

ODBCdriver2

Database specificfunction calls

Standard QueryLanguage

Standard functions

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Database Management using ODBC

Database1API1 Application

SQLcommands

ODBCfunction calls

SQL

ODBCfunctions

Database2API1

SQL

ODBCfunctions

ODBCdriver2

ODBCdriver1

ODBCdriver2

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videoteka

Registration

Videoteka„MySQL” driver

DSN (Data Source Name)Driver

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Vezérlőpult/Felügyeleti eszközök

Registration

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ODBC datasource

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Identification of„physical”database.

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Available Drivers in Qt

•QDB2 - IBM DB2 Driver (v7.1 and higher) •QIBASE - Borland Interbase Driver •QMYSQL3 - MySQL Driver•QOCI8 - Oracle Call Interface Driver, version 8 and 9 •QODBC3 - Open Database Connectivity Driver•QPSQL7 - PostgreSQL v6.x and v7.x Driver •QSQLITE - SQLite Driver •QTDS7 - Sybase Adaptive Server and Microsoft SQL Server Driver

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Qt / SQL module

DBMS classes canbe found in SQL

Module .

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Database Related Classes

QSqlQuery QSqlCursor

QDataTableQTable

„Represent” data

„Display” data18

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Creating the „Videoteka” project

File/New

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Creating the Main Window

File/New

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Wizard: Choose menus and toolbars

We don’t needthese „services”.

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Wizard: Setup Toolbar

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Wizard: Finish

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Previewing the Project

Ctrl+T

1. qmake –o Makefile videoteka.pro2. nmake3. quit

OR: Build

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The Starting Project

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Adding main program to the project

File/New

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The generated main program

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Compile & Run

1. qmake –o Makefile videoteka.pro2. nmake3. quit

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Connecting to the Database

connection.cpp

connection.h

main.cpp

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Adding Source File to the Project

File/New

File/Save as …

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Adding Header File to the Project

File/New

File/Save as …

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Database Connection: connection.h, connection.cpp

#define DB_SOURCE_DRIVER "QODBC3"#define DB_SOURCE_DBNAME „videoteka"#define DB_SOURCE_USER "nacsa"#define DB_SOURCE_PASSWD "1234"#define DB_SOURCE_HOST "localhost"bool createConnections();

#include <qsqldatabase.h>#include "connection.h"bool createConnections() {

QSqlDatabase *source = QSqlDatabase::addDatabase( DB_SOURCE_DRIVER);source->setDatabaseName( DB_SOURCE_DBNAME );source->setUserName( DB_SOURCE_USER );source->setPassword( DB_SOURCE_PASSWD );source->setHostName( DB_SOURCE_HOST );if ( ! source->open() ) {qWarning( „Failed to open database: " +source->lastError().driverText() );qWarning( source->lastError().databaseText() );return FALSE;

}return TRUE;

}

1.Activate driver2.Set connection’s properties3.Open connection

connection.h

connection.cpp

Only the driver has tobe modified changingthe databaseenvironment.

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Database Connection: main.cpp

. . .#include <qsqldatabase.h>#include "connection.h. . .int main( int argc, char *argv[] ) {

. . .if ( createConnections() ) {

// We have opened the database connections.// Ready to perform SQL commands

}return 0;}

main.cpp

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Creating New Action – Tables/Customers

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tableCustomersAction: Properties

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tableFilmsAction: Properties

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tableRentsAction: Properties

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Adding Actions to the Menu

Drag & Drop

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Creating CustomersForm

File/New

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Drag & Drop & . . .

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Data Table Wizard: Choose Database & Table

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Data Table Wizard: Choose Database & Table

customersfilmsrentssequence

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Data Table Wizard: Displayed Fields

nameaddresscode

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Data Table Wizard: Table Properties

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Data Table Wizard: SQL

You can add a valid WHERE clause here.

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Double Click ontable to edit it.

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Bringing up the CustomersForm

CustomersForm

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Creating a New Slot

Function: slotTableCustomers()Return type: voidSpecifier: virtualAccess: publicType: slot

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Connections

Sender: tableCustomersActionSignal: activated()Receiver: MainFormSlot:slotTableCustomers()

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Further Slots

Function: slotTableFilms()Return type: voidSpecifier: virtualAccess: publicType: slot

Function: slotTableRents()Return type: voidSpecifier: virtualAccess: publicType: slot

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Further Connections

Sender: tableFilmsActionSignal: activated()Receiver: MainFormSlot:slotTableFilms()

Sender: tableRentsActionSignal: activated()Receiver: MainFormSlot:slotTableRents()

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Implementation: slotTableCustomers

void MainForm::slotTableCustomers(){statusBar()->message(tr(QString::fromUtf8("Loading Table of Customers . . .")));setCaption(tr(QString::fromUtf8("Videoteka: Table of Customers ")));CustomersForm *customersForm = new CustomersForm(this, "CustomersForm");customersForm->show();setCentralWidget(customersForm);statusBar()->message(tr(QString::fromUtf8("Ready")));

}

mainform.ui.h

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Implementation: slotTableFilms()

void MainForm::slotTableFilms(){

QMessageBox::information( this, "Videoteka Manager","Sorry! Not implemented yet." );

}

mainform.ui.h

Implementation: slotTableRents()

void MainForm::slotTableRents(){

QMessageBox::information( this, "Videoteka Manager","Sorry! Not implemented yet." );

}

mainform.ui.h

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DataTable: Signals

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New Slot: slotPrimeInsert()

Function: slotPrimeInsert(QSqlRecord*)Return type: voidSpecifier: virtualAccess: publicType: slot

Edit/Slots …

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Connection

Sender: dataTableSignal: primeInsert(QSqlRecord*)Receiver: MainFormSlot:slotPrimeInsert(QSqlRecord*)

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Implementation

void CustomersForm::slotPrimeInser( QSqlRecord *buffer ){

QSqlQuery query;query.exec("UPDATE sequence SET sequence = sequence + 1 WHERE tablename

='customers';");query.exec("SELECT sequence FROM sequence WHERE tablename ='customers';");if (query.next()) {

buffer->setValue("customer_id", query.value(0));}

}

customerform.ui.h

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Controlling Data Entry

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Slot: slotCurrentChanged()

Function: slotCurrentChanged(QSqlRecord*)Return type: voidSpecifier: virtualAccess: publicType: slot

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Function: setMode()

Function: setMode(QSqlRecord*)Return type: voidSpecifier: virtualAccess: protectedType: function

Edit/Slots …

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Implementation: slotCurrentChanged(), setMode()

void CustomersForm::slotCurrentChanged( QSqlRecord * buffer ){

setMode(buffer);}

void CustomersForm::setMode( QSqlRecord * buffer ){

if (buffer == 0) return;QSqlQuery query;int count_rent=0;query.exec( "SELECT count(*) FROM rents WHERE customer_id=" +

buffer->value("customer_id").toString() + ";" );if (query.next())

count_rent = query.value(0).toInt();if ( count_rent == 0)

dataTable->sqlCursor ()->setMode( QSqlCursor::Insert | QSqlCursor::Delete | QSqlCursor::Update );

elsedataTable->sqlCursor ()->setMode( QSqlCursor::Insert | QSqlCursor::Update );

}

customerform.ui.h

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Compile & Run

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Compile & Run

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ComboBox

Modificationwith controls

Calculated field

Calculatedfield with

„info”

Read Only

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Classes

QSqlCursor

FilmSqlCursorQDataTable

FilmDataTable

QMainWindow

Videoteka

main.cpp

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Classes

QSqlCursor

FilmSqlCursorQDataTable

FilmDataTable

QMainWindow

Videoteka

main.cpp70

FilmSqlCursor - Definition

#include <qsqlcursor.h>

class FilmSqlCursor : public QSqlCursor {public:FilmSqlCursor();

protected:

QVariant calculateField(const QString &name);

};

filmsqlcursor.h

Protected virtual function which is called whenever a field needs to be calculated. If calculated fields are being used, derived classes must reimplement this function.

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FilmSqlCursor - Implementation#include "filmsqlcursor.h"

FilmSqlCursor::FilmSqlCursor(): QSqlCursor("films"){

QSqlFieldInfo available("available", QVariant::Int);append(available);setCalculated(available.name(),TRUE);

}

QVariant FilmSqlCursor::calculateField(const QString &name){

if (name == "available") {QSqlQuery query;int available=0;query.exec("SELECT (amount - rented) FROM films WHERE film_id=" +

field("film_id")->value().toString() + ";");if (query.next())

available = query.value(0).toInt();return QVariant(QString::number(available));

}return QVariant(QString::null);

}

filmsqlcursor.cpp

The field „available” is a calculated field.

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Classes

QSqlCursor

FilmSqlCursorQDataTable

FilmDataTable

QMainWindow

Videoteka

main.cpp

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Preparing FilmDataTable Class

File/New/C++ Cource FileSave As:filmdatatable.cpp

File/New/C++ Cource FileSave As:filmdatatable.h

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FilmDataTable: Definitionclass FilmSqlCursor;

class FilmDataTable : public QDataTable{Q_OBJECTpublic:FilmDataTable(QWidget * parent =0 , const char * name =0 );void paintField(

QPainter * p, const QSqlField* field, const QRect & cr, bool );

public slots:void slotPrimeInsert(QSqlRecord*);void slotCurrentChanged(QSqlRecord* buffer);void slotBeforeUpdate(QSqlRecord* buffer);

private:void setMode(QSqlRecord* buffer);

private:FilmSqlCursor *cursor;QSqlPropertyMap *propMap;FilmSqlEditorFactory *editorFactory;

};

filmdatatable.h

#include <qdatatable.h>#include <qpainter.h>#include <qsqleditorfactory.h>#include <qsqlpropertymap.h>

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FilmDataTable: Constructor /BasicsFilmDataTable::FilmDataTable(

QWidget * parent, const char * name) :QDataTable( parent, name )

{cursor = new FilmSqlCursor();setSqlCursor(cursor);//addColumn( "film_id", "Id" );addColumn( "title", tr(QString::fromUtf8("Title")) );addColumn( "type", tr(QString::fromUtf8("Type")) );addColumn( "amount", tr(QString::fromUtf8("Amount")) );addColumn( "rented", tr(QString::fromUtf8("Rented")) );addColumn( "available", tr(QString::fromUtf8("Available")) );//setColumnWidth(1,200);refresh();setConfirmDelete(TRUE);setAutoEdit(TRUE);. . .

}

filmdatatable.cpp

#include "filmdatatable.h"#include "filmsqlcursor.h"#include <qmessagebox.h>

#include "typepicker.h"#include "readonlyedit.h"

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FilmDataTable: Constructor /Property & Factory

FilmDataTable::FilmDataTable(QWidget * parent, const char * name) :QDataTable( parent, name )

{. . .propMap = new QSqlPropertyMap();propMap->insert( "TypePicker", "type" );installPropertyMap( propMap );

editorFactory = new FilmSqlEditorFactory();installEditorFactory( editorFactory );

. . .

}

filmdatatable.cpp

#include "filmdatatable.h"#include "filmsqlcursor.h"#include <qmessagebox.h>

#include "typepicker.h"#include "readonlyedit.h"

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FilmDataTable: Constructor / ConnectionsFilmDataTable::FilmDataTable(

QWidget * parent, const char * name) :QDataTable( parent, name )

{. . .// signals and slots connectionsconnect( this, SIGNAL( primeInsert(QSqlRecord*) ),

this, SLOT( slotPrimeInsert(QSqlRecord*) ) );connect( this, SIGNAL( currentChanged(QSqlRecord*) ),

this, SLOT( slotCurrentChanged(QSqlRecord*) ) );connect( this, SIGNAL(beforeUpdate(QSqlRecord*) ),

this, SLOT(slotBeforeUpdate(QSqlRecord*) ) );}

filmdatatable.cpp

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FilmDataTable: Destructor

FilmDataTable::~FilmDataTable(){

if (propMap) delete propMap;if (editorFactory) delete editorFactory;if (cursor) delete cursor; //May be it’s not necessary.

}

filmdatatable.cpp

FilmDataTable::FilmDataTable(. . .){cursor = new FilmSqlCursor();. . .propMap = new QSqlPropertyMap();. . .editorFactory = new FilmSqlEditorFactory();. . .

}

filmdatatable.cpp

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FilmDataTable: slotPrimeInsert()void FilmDataTable::slotPrimeInsert(QSqlRecord * buffer){

QSqlQuery query;query.exec("UPDATE sequence SET sequence = sequence + 1 WHERE tablename

='films';");query.exec("SELECT sequence FROM sequence WHERE tablename ='films';");if (query.next()) {

buffer->setValue("film_id", query.value(0));buffer->setValue("amount",1);buffer->setValue("rented",0);buffer->setValue("available",1);buffer->setValue("type","DVD");

}

}

filmdatatable.cpp

Default values starting insertion.

Default calculatedvalue must be done, TOO, otherwise thisvalue remains zero.

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FilmDataTable: slotBeforeUpdate()

void FilmDataTable::slotBeforeUpdate(QSqlRecord* buffer){if(buffer->value("amount").toInt() < buffer->value("rented").toInt()) {buffer->setValue("amount",buffer->value("rented"));QMessageBox::information( this,

tr(QString::fromUtf8("Videoteka: Updating Table of Films")),tr(QString::fromUtf8("Amount can not be less then number of rented films.!")));

}}

filmdatatable.cpp

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FilmDataTable: setMode()void FilmDataTable::setMode(QSqlRecord* buffer){

if (buffer == 0) return;QSqlQuery query;int count_rented=0;query.exec( "SELECT rented FROM films WHERE film_id=" +

buffer->value("film_id").toString() + ";" );if (query.next())

count_rented = query.value(0).toInt();if ( count_rented == 0)

cursor->setMode( QSqlCursor::Insert | QSqlCursor::Delete | QSqlCursor::Update );else

cursor->setMode( QSqlCursor::Insert | QSqlCursor::Update );}

filmdatatable.cpp

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Reimplementation of paintField()void FilmDataTable::paintField( QPainter * p, const QSqlField* field,const QRect & cr, bool b){

if ( !field )return;

if ( field->name() == "available" ) {QString text;if(field->value().toInt() == 0)text="* Out of stock*";

elsetext = field->value().toString();p->drawText( 2,2, cr.width()-4, cr.height()-4, fieldAlignment( field ), text );

} else {QDataTable::paintField( p, field, cr, b) ;

}}

filmdatatable.cpp

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FilmSqlEditorFactory: Definition(embedded!)

class FilmSqlEditorFactory : public QSqlEditorFactory{

Q_OBJECTpublic:

QWidget *createEditor( QWidget *parent, const QSqlField *field );};

filmdatatable.h

To create „custom” editor you haveto reimlement createEditor() function.

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FilmSqlEditorFactory: Implementation (embedded!)

. . .QWidget *FilmSqlEditorFactory::createEditor(

QWidget *parent, const QSqlField *field ){

if ( field->name() == "rented" ) {QWidget *editor = new ReadOnlyEdit( parent );return editor;

}if ( field->name() == "type" ) {

QWidget *editor = new TypePicker( parent );return editor;

}if ( field->name() == "available" ) {

QWidget *editor = new ReadOnlyEdit( parent );return editor;

} return QSqlEditorFactory::createEditor( parent, field );

}. . .

filmdatatable.cpp

For these three fields we wan to touse „custom” editor.(These two classes will be given later!)

TypePicker Editor

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ReadOnlyEdit Class

#include <qlineedit.h>class ReadOnlyEdit : public QLineEdit {

Q_OBJECTpublic:

ReadOnlyEdit( QWidget *parent=0, const char *name=0 );};

readonlyedit.h

#include "readonlyedit.h"ReadOnlyEdit::ReadOnlyEdit( QWidget *parent, const char *name ) : QLineEdit( parent, name ){

setReadOnly(TRUE);

}

readonlyedit.cpp

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TypePicker Class: Definition#include <qcombobox.h>class TypePicker : public QComboBox{Q_OBJECT

Q_PROPERTY( QString type READ Type WRITE setType )

public:TypePicker( QWidget *parent=0, const char *name=0 );QString Type() const;void setType( QString type );

};

typepicker.h

memberread() write()

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#include "typepicker.h"#include <qsqlcursor.h>TypePicker::TypePicker( QWidget *parent, const char *name ) : QComboBox( parent, name ){

insertItem("DVD");insertItem("VHS");setCurrentText("DVD");

}

QString TypePicker::Type() const{

return currentText();}

void TypePicker::setType( QString type ){

setCurrentText( type );}

TypePicker Class: Definition

typepicker.h

read()

write()

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Reads and writesReadingGenerates#includesToolGenerated source fileRevision controlled source file

SummaryQt

designer

UIC

form.cpp main.cpp

form.ui

form.h

form.ui

Application specific functions can be given

in form.ui.h file.

form.ui.h

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Summary: Creating Dialogs

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Summary: Creating Main Windows

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Summary: Database Related Application

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