mainwindow.h:

#ifndef MAINWINDOW_H

#define MAINWINDOW_H

#include <QMainWindow>

class MainWindow : public QMainWindow

{

    Q_OBJECT

public:

    MainWindow(QWidget *parent = 0);

    ~MainWindow();

    private slots:

     void open();

private:

     QAction *openAction;

};

#endif // MAINWINDOW_H

mainwindow.cpp:

#include "mainwindow.h"

#include<QAction>

#include<QMessageBox>

#include<QMenuBar>

#include<QStatusBar>

#include<QToolBar>

MainWindow::MainWindow(QWidget *parent)

    : QMainWindow(parent)

{

    setWindowTitle(tr("Main Windonw"));

    openAction=new QAction(QIcon(":/file3.jpg"),tr("&open..."),this);

    openAction->setShortcuts(QKeySequence::Open);

    openAction->setStatusTip(tr("open an existing file"));

    connect(openAction,&QAction::triggered,this,&MainWindow::open);

    QMenu *file=menuBar()->addMenu(tr("&File"));

    file->addAction(openAction);

    QToolBar *toolBar=addToolBar(tr("&File"));

    toolBar->addAction(openAction);

    QStatusBar *status=statusBar();

    status->addAction(openAction);

this->addAction(openAction);

    this->setContextMenuPolicy(Qt::ActionsContextMenu);

}

 void MainWindow::open()

 {

     QMessageBox::information(this,tr("information"),tr("open"));

 }

MainWindow::~MainWindow()

{

}