Dialog.h:

#ifndef DIALOG_H
 #define DIALOG_H

 #include <QDialog>

 class QAction;
 class QDialogButtonBox;
 class QGroupBox;
 class QLabel;
 class QLineEdit;
 class QMenu;
 class QMenuBar;
 class QPushButton;
 class QTextEdit;

 class Dialog : public QDialog
 {
     Q_OBJECT

 public:
     Dialog();

 private:
     void createMenu();
     void createHorizontalGroupBox();
     void createGridGroupBox();
     void createFormGroupBox();

     enum { NumGridRows = 3, NumButtons = 4 };

     QMenuBar *menuBar;
     QGroupBox *horizontalGroupBox;
     QGroupBox *gridGroupBox;
     QGroupBox *formGroupBox;
     QTextEdit *smallEditor;
     QTextEdit *bigEditor;
     QLabel *labels[NumGridRows];
     QLineEdit *lineEdits[NumGridRows];
     QPushButton *buttons[NumButtons];
     QDialogButtonBox *buttonBox;

     QMenu *fileMenu;
     QAction *exitAction;
 };

 #endif

-----------------------------------------------------------------
Dialog.cpp:

#include <QtGui>

 #include "dialog.h"

 Dialog::Dialog()
 {
     createMenu();
     createHorizontalGroupBox();
     createGridGroupBox();
     createFormGroupBox();

     bigEditor = new QTextEdit;
     bigEditor->setPlainText(tr("This widget takes up all the remaining space "
                                "in the top-level layout."));

     buttonBox = new QDialogButtonBox(QDialogButtonBox::Ok
                                      | QDialogButtonBox::Cancel);

     connect(buttonBox, SIGNAL(accepted()), this, SLOT(accept()));
     connect(buttonBox, SIGNAL(rejected()), this, SLOT(reject()));

     QVBoxLayout *mainLayout = new QVBoxLayout;
     mainLayout->setMenuBar(menuBar);
     mainLayout->addWidget(horizontalGroupBox);
     mainLayout->addWidget(gridGroupBox);
     mainLayout->addWidget(formGroupBox);
     mainLayout->addWidget(bigEditor);
     mainLayout->addWidget(buttonBox);
     setLayout(mainLayout);

     setWindowTitle(tr("Basic Layouts"));
 }

 void Dialog::createMenu()
 {
     menuBar = new QMenuBar;

     fileMenu = new QMenu(tr("&File"), this);
     exitAction = fileMenu->addAction(tr("E&xit"));
     menuBar->addMenu(fileMenu);

     connect(exitAction, SIGNAL(triggered()), this, SLOT(accept()));
 }

 void Dialog::createHorizontalGroupBox()
 {
     horizontalGroupBox = new QGroupBox(tr("Horizontal layout"));
     QHBoxLayout *layout = new QHBoxLayout;

     for (int i = 0; i < NumButtons; ++i) {
         buttons[i] = new QPushButton(tr("Button %1").arg(i + 1));
         layout->addWidget(buttons[i]);
     }
     horizontalGroupBox->setLayout(layout);
 }

 void Dialog::createGridGroupBox()
 {
     gridGroupBox = new QGroupBox(tr("Grid layout"));
     QGridLayout *layout = new QGridLayout;

     for (int i = 0; i < NumGridRows; ++i) {
         labels[i] = new QLabel(tr("Line %1:").arg(i + 1));
         lineEdits[i] = new QLineEdit;
         layout->addWidget(labels[i], i + 1, 0);
         layout->addWidget(lineEdits[i], i + 1, 1);
     }

     smallEditor = new QTextEdit;
     smallEditor->setPlainText(tr("This widget takes up about two thirds of the "
                                  "grid layout."));
     layout->addWidget(smallEditor, 0, 2, 4, 1);

     layout->setColumnStretch(1, 10);
     layout->setColumnStretch(2, 20);
     gridGroupBox->setLayout(layout);
 }

 void Dialog::createFormGroupBox()
 {
     formGroupBox = new QGroupBox(tr("Form layout"));
     QFormLayout *layout = new QFormLayout;
     layout->addRow(new QLabel(tr("Line 1:")), new QLineEdit);
     layout->addRow(new QLabel(tr("Line 2, long text:")), new QComboBox);
     layout->addRow(new QLabel(tr("Line 3:")), new QSpinBox);
     formGroupBox->setLayout(layout);
 }

----------------------------------------------------------------------------
main.cpp:

#include <QApplication>

#include "dialog.h"

int main(int argc, char *argv[])
{
    QApplication app(argc, argv);
    Dialog dialog;
    return dialog.exec();
}