Question

I’m starting using Qt for a GUI, but I have some problems with headers/libraries because I’m missing some functions.

Two of them are:

<obj_name>.setModal(true);
<obj_name>.exec();

They should work fine as in the video I’m following (at 6:30).

Because I did exactly what they did, so my clue is his version isn’t the same as mine.

I want to know which header should I include.

Here’s my code:

void MainWindow::on_actionNew_Window_triggered()
{
    MyDialog mDialog;
    mDialog.setModal(true);
    mDialog.exec();

}

Even with:

#include <QDialog>

Still doesn’t work. It says:

C:\QtSDK\teste-build-desktop-Qt_4_8_1_for_Desktop_-MinGW_Qt_SDK__Debug..\teste\mainwindow.cpp:22: error: ‘class MyDialog’ has no member named ‘setModal’.

mydialog.h code:

#ifndef MYDIALOG_H
#define MYDIALOG_H

#include <QMainWindow>
#include <QDialog>

namespace Ui {
class MyDialog;
}

class MyDialog : public QMainWindow
{
    Q_OBJECT

public:
    explicit MyDialog(QWidget *parent = 0);
    ~MyDialog();

private:
    Ui::MyDialog *ui;
};

#endif // MYDIALOG_H

It is included in mainwindow.cpp and mydialog.cpp (the header is just the class).

Answer 1

MyDialog is no QDialog. You created it as a “main window” which is no dialog.

To hot-fix this (without recreating the dialog using QtCreator), just rewrite the inheritance in mydialog.h
from:

class MyDialog : public QMainWindow

to:

class MyDialog : public QDialog

In your mydialog.cpp you find the implementation of the constructor of MyDialog which calls the superclass constructor. Since we just changed the superclass, we also have to change this call from:

MyDialog::MyDialog(QWidget *parent) :
    QMainWindow(parent)
...

to

MyDialog::MyDialog(QWidget *parent) :
    QDialog(parent)
...

You also have to fix your .ui file to morph the whole widget from a main window to a dialog. I’ll add how to do so in a few minutes (have to find it out) You don’t need to touch the .ui file.