how to add menu dynamically in Qt

Answer 1

Such code should work:

QMainWindow wnd;
QAction *act = wnd.menuBar()->addMenu("SomeMenu")->addMenu("someSubmenu")->addAction("someAction");
QObject::connect(act,SIGNAL(triggered()),
                 someObj,SLOT(actionReaction()));

I think addMenu() addAction() should work in more reliable way. This approach works for me.

Answer 2

I'm not sure to understand exactly what you're willing to do into your Move() slot.

But here is your own code (I removed what seemed useless to me), modified so that it is not crashing on my computer :

mainwindow.h

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>

#include <QAction>
#include <QMenu>

class MainWindow : public QMainWindow
{
   Q_OBJECT

public:
   explicit MainWindow(QWidget *parent = 0);

private:
   QMenu* menu;
   QAction *dummyaction;
   QMenu* m_pSubMenu;
 private slots:
    void Move();
};

#endif // MAINWINDOW_H

mainwindow.cpp :

#include "mainwindow.h"

#include <QMenuBar>

MainWindow::MainWindow(QWidget *parent) : QMainWindow(parent)
{
   m_pSubMenu = NULL;
   QMenuBar* pMenuBar = new QMenuBar(this);

   setMenuBar(pMenuBar);

   dummyaction = new QAction("Testing",this);
   menu = new QMenu("Test", this);
   menu->addAction(dummyaction);
   this->menuBar()->addMenu(menu);

   connect(menu, SIGNAL(aboutToShow()), this, SLOT(Move()));
}

void MainWindow::Move() {
   if (!m_pSubMenu) {
      m_pSubMenu = new QMenu(menu);
      dummyaction->setMenu(m_pSubMenu);
   }
   QAction* pAction = new QAction("Test", this);
   m_pSubMenu->addAction(pAction);
}

I don't know exactly what you want to do into your Move() slot, but as an example, each time the Move() slot is called, a new submenu item is added.

Hope this helps.