Qt show modal dialog (.ui) on menu item click

Question

I want to make a simple \'About\' modal dialog, called from Help->About application menu. I\'ve created a modal dialog window with QT Creator (.ui file).

What code shou

Answer 1

You need to setup the dialog with the UI you from your .ui file. The Qt uic compiler generates a header file from your .ui file which you need to include in your code. Assumed that your .ui file is called about.ui, and the Dialog is named About, then uiccreates the file ui_about.h, containing a class Ui_About. There are different approaches to setup your UI, at simplest you can do

#include "ui_about.h"

...

void MainWindow::on_actionAbout_triggered()
{
    about = new QDialog(0,0);

    Ui_About aboutUi;
    aboutUi.setupUi(about);

    about->show();
}

A better approach is to use inheritance, since it encapsulates your dialogs better, so that you can implement any functionality specific to the particular dialog within the sub class:

AboutDialog.h:

#include 
#include "ui_about.h"

class AboutDialog : public QDialog, public Ui::About {
    Q_OBJECT

public:
    AboutDialog( QWidget * parent = 0);
};

AboutDialog.cpp:

AboutDialog::AboutDialog( QWidget * parent) : QDialog(parent) {

    setupUi(this);

    // perform additional setup here ...
}

Usage:

#include "AboutDialog.h"

...

void MainWindow::on_actionAbout_triggered() {
    about = new AboutDialog(this);
    about->show();
}

In any case, the important code is to call the setupUi() method.

BTW: Your dialog in the code above is non-modal. To show a modal dialog, either set the windowModality flag of your dialog to Qt::ApplicationModal or use exec() instead of show().