close button on qDialog only closing on second click - qt

Question

I'm trying to generate a dialog that contains an ad-on tool that is separate from my main program, it its triggered from an action within the menus.
I've got the following code:
void MainWindow::on_actionCalibration_Tool_triggered()
{
QGridLayout *grid = new QGridLayout;
NewDialog.setLayout(grid);
NewDialog.setMinimumHeight(500);
NewDialog.setMinimumWidth(800);
QLabel *label = new QLabel;
QFont sansFont("MS Shell Dlg 2",22, QFont::Bold);
label->setText("Test");
label->setFont(sansFont);
QPushButton *okbutton = new QPushButton;
QPushButton *closebutton = new QPushButton;
okbutton->setText("Ok");
closebutton->setText("Close");
QTimer *timer = new QTimer;
connect(okbutton,SIGNAL(clicked()),this,SLOT(on_ScanpB_clicked()));
connect(closebutton,SIGNAL(clicked()),this,SLOT(CloseDialog()));
grid->addWidget(label);
grid->addWidget(okbutton);
grid->addWidget(closebutton);
NewDialog.exec();
NewDialog.show();
}
void MainWindow::CloseDialog()
{
NewDialog.close();
}
With NewDialog being defined in main window.h as a QDialog.
My issue is when I click the close button, the dialog will close for a split second then reopen, after I click the close button for a second time it closes for good.
Is there any better implementation or way around this?
Thanks

Answer 1

You should not call QDialog::show and QDialog::exec. Instead, pick one to call.
Use exec if you want to block user interaction with the dialog's parent while the dialog is open. The user will not be play with anything else in the application until they dismiss the dialog. This is called a modal.
Use show if you want to allow the user to work with the dialog and the rest of the application at the same time.
Usually you'd choose exec. It is easier to work with. In your case, you displayed the dialog twice by calling both functions.