Displaying windows in a loop

[apalomer]

Hello,

I am new to Qt and I don't know how to properly do this. I want to create a window with a message at each iteration of a for loop and wait until the user closes that window before continuing the for loop. Something like:

int main(int argc, char **argv)
{
  for (int i=0;i<10;i++){
    QApplication app (argc, argv);
    QPushButton button (QString::number(2*i));
    button.show();
    app.exec();
  }
  return 0;
}

However, this gives me the error at the end of this post. Any idea on how to solve this issue? It is not criticall because the program runs, however, it is anoying to see this in the terminal.

Thank you very muchQ

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_container_add: assertion 'GTK_IS_CONTAINER (container)' failed

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_widget_realize: assertion 'GTK_WIDGET_ANCHORED (widget) || GTK_IS_INVISIBLE (widget)' failed

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_widget_realize: assertion 'GTK_WIDGET_ANCHORED (widget) || GTK_IS_INVISIBLE (widget)' failed

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_container_add: assertion 'GTK_IS_CONTAINER (container)' failed

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_widget_realize: assertion 'GTK_WIDGET_ANCHORED (widget) || GTK_IS_INVISIBLE (widget)' failed

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_widget_realize: assertion 'GTK_WIDGET_ANCHORED (widget) || GTK_IS_INVISIBLE (widget)' failed

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_widget_realize: assertion 'GTK_WIDGET_ANCHORED (widget) || GTK_IS_INVISIBLE (widget)' failed

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_widget_realize: assertion 'GTK_WIDGET_ANCHORED (widget) || GTK_IS_INVISIBLE (widget)' failed

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_container_add: assertion 'GTK_IS_CONTAINER (container)' failed

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_widget_realize: assertion 'GTK_WIDGET_ANCHORED (widget) || GTK_IS_INVISIBLE (widget)' failed

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_widget_realize: assertion 'GTK_WIDGET_ANCHORED (widget) || GTK_IS_INVISIBLE (widget)' failed

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_container_add: assertion 'GTK_IS_CONTAINER (container)' failed

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_widget_realize: assertion 'GTK_WIDGET_ANCHORED (widget) || GTK_IS_INVISIBLE (widget)' failed

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_widget_realize: assertion 'GTK_WIDGET_ANCHORED (widget) || GTK_IS_INVISIBLE (widget)' failed

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_container_add: assertion 'GTK_IS_CONTAINER (container)' failed

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_widget_realize: assertion 'GTK_WIDGET_ANCHORED (widget) || GTK_IS_INVISIBLE (widget)' failed

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_widget_realize: assertion 'GTK_WIDGET_ANCHORED (widget) || GTK_IS_INVISIBLE (widget)' failed

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_container_add: assertion 'GTK_IS_CONTAINER (container)' failed

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_widget_realize: assertion 'GTK_WIDGET_ANCHORED (widget) || GTK_IS_INVISIBLE (widget)' failed

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_widget_realize: assertion 'GTK_WIDGET_ANCHORED (widget) || GTK_IS_INVISIBLE (widget)' failed

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_container_add: assertion 'GTK_IS_CONTAINER (container)' failed

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_widget_realize: assertion 'GTK_WIDGET_ANCHORED (widget) || GTK_IS_INVISIBLE (widget)' failed

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_widget_realize: assertion 'GTK_WIDGET_ANCHORED (widget) || GTK_IS_INVISIBLE (widget)' failed

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_widget_realize: assertion 'GTK_WIDGET_ANCHORED (widget) || GTK_IS_INVISIBLE (widget)' failed

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_widget_realize: assertion 'GTK_WIDGET_ANCHORED (widget) || GTK_IS_INVISIBLE (widget)' failed

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_widget_realize: assertion 'GTK_WIDGET_ANCHORED (widget) || GTK_IS_INVISIBLE (widget)' failed

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_widget_realize: assertion 'GTK_WIDGET_ANCHORED (widget) || GTK_IS_INVISIBLE (widget)' failed

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_widget_realize: assertion 'GTK_WIDGET_ANCHORED (widget) || GTK_IS_INVISIBLE (widget)' failed

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_container_add: assertion 'GTK_IS_CONTAINER (container)' failed

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_widget_realize: assertion 'GTK_WIDGET_ANCHORED (widget) || GTK_IS_INVISIBLE (widget)' failed

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_widget_realize: assertion 'GTK_WIDGET_ANCHORED (widget) || GTK_IS_INVISIBLE (widget)' failed

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_widget_realize: assertion 'GTK_WIDGET_ANCHORED (widget) || GTK_IS_INVISIBLE (widget)' failed

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_widget_realize: assertion 'GTK_WIDGET_ANCHORED (widget) || GTK_IS_INVISIBLE (widget)' failed

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_widget_realize: assertion 'GTK_WIDGET_ANCHORED (widget) || GTK_IS_INVISIBLE (widget)' failed

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_widget_realize: assertion 'GTK_WIDGET_ANCHORED (widget) || GTK_IS_INVISIBLE (widget)' failed

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_container_add: assertion 'GTK_IS_CONTAINER (container)' failed

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_widget_realize: assertion 'GTK_WIDGET_ANCHORED (widget) || GTK_IS_INVISIBLE (widget)' failed

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_widget_realize: assertion 'GTK_WIDGET_ANCHORED (widget) || GTK_IS_INVISIBLE (widget)' failed

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_container_add: assertion 'GTK_IS_CONTAINER (container)' failed

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_widget_realize: assertion 'GTK_WIDGET_ANCHORED (widget) || GTK_IS_INVISIBLE (widget)' failed

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_widget_realize: assertion 'GTK_WIDGET_ANCHORED (widget) || GTK_IS_INVISIBLE (widget)' failed

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_container_add: assertion 'GTK_IS_CONTAINER (container)' failed

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_widget_realize: assertion 'GTK_WIDGET_ANCHORED (widget) || GTK_IS_INVISIBLE (widget)' failed

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_widget_realize: assertion 'GTK_WIDGET_ANCHORED (widget) || GTK_IS_INVISIBLE (widget)' failed

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_widget_realize: assertion 'GTK_WIDGET_ANCHORED (widget) || GTK_IS_INVISIBLE (widget)' failed

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_container_add: assertion 'GTK_IS_CONTAINER (container)' failed

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_widget_realize: assertion 'GTK_WIDGET_ANCHORED (widget) || GTK_IS_INVISIBLE (widget)' failed

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_widget_realize: assertion 'GTK_WIDGET_ANCHORED (widget) || GTK_IS_INVISIBLE (widget)' failed

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_widget_realize: assertion 'GTK_WIDGET_ANCHORED (widget) || GTK_IS_INVISIBLE (widget)' failed

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_widget_realize: assertion 'GTK_WIDGET_ANCHORED (widget) || GTK_IS_INVISIBLE (widget)' failed

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_widget_realize: assertion 'GTK_WIDGET_ANCHORED (widget) || GTK_IS_INVISIBLE (widget)' failed

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_container_add: assertion 'GTK_IS_CONTAINER (container)' failed

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_widget_realize: assertion 'GTK_WIDGET_ANCHORED (widget) || GTK_IS_INVISIBLE (widget)' failed

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_widget_realize: assertion 'GTK_WIDGET_ANCHORED (widget) || GTK_IS_INVISIBLE (widget)' failed

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_container_add: assertion 'GTK_IS_CONTAINER (container)' failed

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_widget_realize: assertion 'GTK_WIDGET_ANCHORED (widget) || GTK_IS_INVISIBLE (widget)' failed

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_widget_realize: assertion 'GTK_WIDGET_ANCHORED (widget) || GTK_IS_INVISIBLE (widget)' failed

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_container_add: assertion 'GTK_IS_CONTAINER (container)' failed

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_widget_realize: assertion 'GTK_WIDGET_ANCHORED (widget) || GTK_IS_INVISIBLE (widget)' failed

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_widget_realize: assertion 'GTK_WIDGET_ANCHORED (widget) || GTK_IS_INVISIBLE (widget)' failed

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_widget_realize: assertion 'GTK_WIDGET_ANCHORED (widget) || GTK_IS_INVISIBLE (widget)' failed

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_widget_realize: assertion 'GTK_WIDGET_ANCHORED (widget) || GTK_IS_INVISIBLE (widget)' failed

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_container_add: assertion 'GTK_IS_CONTAINER (container)' failed

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_widget_realize: assertion 'GTK_WIDGET_ANCHORED (widget) || GTK_IS_INVISIBLE (widget)' failed

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_widget_realize: assertion 'GTK_WIDGET_ANCHORED (widget) || GTK_IS_INVISIBLE (widget)' failed

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_widget_realize: assertion 'GTK_WIDGET_ANCHORED (widget) || GTK_IS_INVISIBLE (widget)' failed

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_widget_realize: assertion 'GTK_WIDGET_ANCHORED (widget) || GTK_IS_INVISIBLE (widget)' failed

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_widget_realize: assertion 'GTK_WIDGET_ANCHORED (widget) || GTK_IS_INVISIBLE (widget)' failed

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_container_add: assertion 'GTK_IS_CONTAINER (container)' failed

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_widget_realize: assertion 'GTK_WIDGET_ANCHORED (widget) || GTK_IS_INVISIBLE (widget)' failed

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_widget_realize: assertion 'GTK_WIDGET_ANCHORED (widget) || GTK_IS_INVISIBLE (widget)' failed

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_container_add: assertion 'GTK_IS_CONTAINER (container)' failed

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_widget_realize: assertion 'GTK_WIDGET_ANCHORED (widget) || GTK_IS_INVISIBLE (widget)' failed

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_widget_realize: assertion 'GTK_WIDGET_ANCHORED (widget) || GTK_IS_INVISIBLE (widget)' failed

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_container_add: assertion 'GTK_IS_CONTAINER (container)' failed

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_widget_realize: assertion 'GTK_WIDGET_ANCHORED (widget) || GTK_IS_INVISIBLE (widget)' failed

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_widget_realize: assertion 'GTK_WIDGET_ANCHORED (widget) || GTK_IS_INVISIBLE (widget)' failed

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_container_add: assertion 'GTK_IS_CONTAINER (container)' failed

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_widget_realize: assertion 'GTK_WIDGET_ANCHORED (widget) || GTK_IS_INVISIBLE (widget)' failed

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_widget_realize: assertion 'GTK_WIDGET_ANCHORED (widget) || GTK_IS_INVISIBLE (widget)' failed

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_widget_realize: assertion 'GTK_WIDGET_ANCHORED (widget) || GTK_IS_INVISIBLE (widget)' failed

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_widget_realize: assertion 'GTK_WIDGET_ANCHORED (widget) || GTK_IS_INVISIBLE (widget)' failed

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_widget_realize: assertion 'GTK_WIDGET_ANCHORED (widget) || GTK_IS_INVISIBLE (widget)' failed

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_container_add: assertion 'GTK_IS_CONTAINER (container)' failed

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_widget_realize: assertion 'GTK_WIDGET_ANCHORED (widget) || GTK_IS_INVISIBLE (widget)' failed

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_widget_realize: assertion 'GTK_WIDGET_ANCHORED (widget) || GTK_IS_INVISIBLE (widget)' failed

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_widget_realize: assertion 'GTK_WIDGET_ANCHORED (widget) || GTK_IS_INVISIBLE (widget)' failed

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_widget_realize: assertion 'GTK_WIDGET_ANCHORED (widget) || GTK_IS_INVISIBLE (widget)' failed

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_widget_realize: assertion 'GTK_WIDGET_ANCHORED (widget) || GTK_IS_INVISIBLE (widget)' failed

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_widget_realize: assertion 'GTK_WIDGET_ANCHORED (widget) || GTK_IS_INVISIBLE (widget)' failed

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_widget_realize: assertion 'GTK_WIDGET_ANCHORED (widget) || GTK_IS_INVISIBLE (widget)' failed

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_widget_realize: assertion 'GTK_WIDGET_ANCHORED (widget) || GTK_IS_INVISIBLE (widget)' failed

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_widget_realize: assertion 'GTK_WIDGET_ANCHORED (widget) || GTK_IS_INVISIBLE (widget)' failed

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_widget_realize: assertion 'GTK_WIDGET_ANCHORED (widget) || GTK_IS_INVISIBLE (widget)' failed

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_widget_realize: assertion 'GTK_WIDGET_ANCHORED (widget) || GTK_IS_INVISIBLE (widget)' failed

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_widget_realize: assertion 'GTK_WIDGET_ANCHORED (widget) || GTK_IS_INVISIBLE (widget)' failed

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_widget_realize: assertion 'GTK_WIDGET_ANCHORED (widget) || GTK_IS_INVISIBLE (widget)' failed

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_widget_realize: assertion 'GTK_WIDGET_ANCHORED (widget) || GTK_IS_INVISIBLE (widget)' failed

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_widget_realize: assertion 'GTK_WIDGET_ANCHORED (widget) || GTK_IS_INVISIBLE (widget)' failed

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_widget_realize: assertion 'GTK_WIDGET_ANCHORED (widget) || GTK_IS_INVISIBLE (widget)' failed

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_widget_realize: assertion 'GTK_WIDGET_ANCHORED (widget) || GTK_IS_INVISIBLE (widget)' failed

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_container_add: assertion 'GTK_IS_CONTAINER (container)' failed

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_widget_realize: assertion 'GTK_WIDGET_ANCHORED (widget) || GTK_IS_INVISIBLE (widget)' failed

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_widget_realize: assertion 'GTK_WIDGET_ANCHORED (widget) || GTK_IS_INVISIBLE (widget)' failed

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_container_add: assertion 'GTK_IS_CONTAINER (container)' failed

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_widget_realize: assertion 'GTK_WIDGET_ANCHORED (widget) || GTK_IS_INVISIBLE (widget)' failed

(helloworld:3074): Gtk-CRITICAL **: IA__gtk_widget_realize: assertion 'GTK_WIDGET_ANCHORED (widget) || GTK_IS_INVISIBLE (widget)' failed

[Eeli K]

@apalomer You are running the application on a Gtk based desktop environment or window manager, aren't you? These messages can't come from Qt. In general GUI applications aren't really meant to be started from command line and if I'm correct about the desktop environment thing these same messages can come with any application if you start them from command line terminal.

[dheerendra]

Don't create qapplication inside for loop. Create only once outside the loop. Also call exec outside the loop. Instead of button use qmessgaebox inside loop. These errors may not be related to qt.

[Eeli K]

@Eeli-K On the other hand, QApplication isn't meant to be created several times per application. Write your own QApplication based class which shows the buttons. Or create a new Qt application with a dialog with the Qt Creator wizard and try to edit that, something like this:

#include <QDialog>
#include <QMessageBox>
#include <QApplication>
#include <QDebug>

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);

    for (int i=0;i<2;i++){
        auto w = new QDialog{};
        w->exec();
    }
    for (int i=0;i<2;i++){
        auto w = new QMessageBox{};
        auto x = w->exec();
        qDebug() << x;
    }

    return a.exec();
}

EDIT: dheerendra submitted while I was editing...

[Chris Kawa]

@Eeli-K That code leaks every instance of dialog and messagebox. Either create the instances on the stack, delete them or use the Qt::WA_DeleteOnClose attribute. In case of a messagebox you can also use the blocking static methods.

[Eeli K]

@Chris-Kawa Yes, that was only a quick example to start from, but I admit we shouldn't spread bad habits. At least I should have mentioned this is not ready for normal use.

[apalomer]

@dheerendra Thank you very much. Moving the QApplication out of the loop solved it. The pushbuton was just to create something I actually need to display a whole GUI that I created.