Window not showing up using show()

[nestorac]

I have some code for opening a window from the main one, but it doesn't work. "Window open." gets printed, then nothing else happens, it's just as if show() didn't do anything. This is invoked from a menu using a connector and an action.

The relevant code:

void test1::openNewWindow()
{
qWarning( "Window open." );

QWidget w(this);
Ui::dialog ventanados;
ventanados.setupUi(&w);
w.setWindowModality(Qt::ApplicationModal);
w.show();
}

[A Former User]

Hi! The problem is that you create the window on the stack inside openNewWindow(), so it gets destroyed immediately when the function returns.

void test1::openNewWindow()
{
qWarning( "Window open." );

QWidget w(this); // <-- w is local to this scope
Ui::dialog ventanados;
ventanados.setupUi(&w);
w.setWindowModality(Qt::ApplicationModal);
w.show(); 
} // <-- scope ends, w gets destroyed

[nestorac]

@Wieland thank you. I have tried it and it is an excellent answer, but I don't still get the clue. I have added a 1sec delay to the function after calling show() to see if the windows appears, no luck. I have made the changes you have proposed, and I now have the following code:

test1.h

#ifndef test1_H
#define test1_H

#include <QMainWindow>
#include <QWidget>

#include "ui_test1.h"

class test1 : public QMainWindow
{
    Q_OBJECT

public:
    test1();
    
public slots:
   void openNewWindow();
   
private:
    QWidget *w;
    Ui::dialog ventanados;
};

#endif // test1_H

test1.cpp

#include "test1.h"

#include <QLabel>
#include <QMenu>
#include <QMenuBar>
#include <QAction>
#include <QDialog>
#include <QtTest/QTest>

test1::test1()
{
    w = new QWidget(this);
    QLabel* label = new QLabel( this );
    label->setText( "Hello World!" );
    setCentralWidget( label );
    QAction* action = new QAction(this);
    action->setText( "Open new window" );
    connect(action, SIGNAL(triggered()), SLOT(openNewWindow()) );
    menuBar()->addMenu( "File" )->addAction( action );
}

void test1::openNewWindow()
{
    ventanados.setupUi(w);
    w->show();
    QTest::qSleep(1000);
}

[A Former User]

The following creates a widget that is a child of your MainWindow:

w = new QWidget(this);

If you want w to be a window on its own, then call the constructor without a parent:
w = new QWidget();

[nestorac]

OMG, thanks!!!

[Chris Kawa]

Parents are important for stacking order and focus management. What's more is in your code you're not deleting it explicitly, so if you don't give it a parent it will leak.
Better than not giving it a parent would be to either use QDialog instead or make it a window via a flag, i.e.:

w = new QWidget(this, Qt::Window);

[nestorac]

It also works! Thank you.