[Qt-interest] unappologetic app crash if statusbar used outside of QMainWindow | example provided

[Malyushytsky, Alex]

Debugger is your friend.
Also I would recommend you to revise design of your classes.
At the first glance it should not be working as is without Status bar.
How many HomeWindow/ CentralPage instances are created?

Lets look:

1 .HomeWindow homeWin("W00+!"); // constructor of HomeWindow is called

// inside  HomeWindow constructor new CentralPage is instantiated:

2. CentralPage *centralPageWidget = new CentralPage("test", this); // Since  is derived from CentralPage, HomeWindow constructor will be called (HomeWindow instance 2)


// when HomeWindow instance 2 is constructed it will call line above again.

Process will never end. I don't think that is what you wanted.

Regards,
   Alex





From: qt-interest-bounces at trolltech.com [mailto:qt-interest-bounces at trolltech.com] On Behalf Of S. Aguinaga
Sent: Thursday, March 25, 2010 12:29 PM
To: Qt Interest
Subject: [Qt-interest] unappologetic app crash if statusbar used outside of QMainWindow | example provided

Hello Fellows,

I have started using the Qt example layout "borderlayout", where I create  North Central and South panels.
I needed a statusBar so I simply added a qlabel to the South widget, but when I 'setText' nothing happens, when this is being called from the Central Widget.  So I changed things around where I created a QStatusBar object in the mainwindow, and then tried to access it from the Central Widget.

I even inherited the mainwindow (which I call  the Home Window) into the Central Widget.
And if I try to access the status bar, the whole app crashes.  I created a simple project to demonstrate the issue.  My question is: How do I access a statusbar object from a centralWidget class that is derived from QWidget?

Let me know if you'd like me to post the source files for download.
// Salvador
// Northwestern University

=== main.cpp ==
#include <QApplication>

#include "homewindow.h"

int main(int argc, char *argv[])
{
    QApplication app(argc, argv);
    app.setOrganizationName("Trolltech");
    app.setApplicationName("Application Example");

    HomeWindow homeWin("W00+!");
    homeWin.show();
    return app.exec();
}
==== homewindow.h =====
#include <QtGui>
#include <QWidget>
#include <QStatusBar>
#include "borderlayout.h"

class HomeWindow;

QT_BEGIN_NAMESPACE
class QAction;
class QMenu;
class QPlainTextEdit;
QT_END_NAMESPACE

//! [0]
class HomeWindow : public QWidget
{
    Q_OBJECT

public:
    HomeWindow(){};
    HomeWindow( const QString, QWidget *parent=0);

    QStatusBar *southWidget;
    BorderLayout *layout;

};
class CentralPage : public HomeWindow
{
    Q_OBJECT

public:
    CentralPage(const QString &, QWidget *parent = 0);

public slots:
    void btnSlot();
};

===== homewindow.cpp =====
#include <QtGui>
#include "borderlayout.h"
#include "homewindow.h"

HomeWindow::HomeWindow(const QString xperimenter, QWidget *parent )
    : QWidget(parent)
{
    // central Widget
    CentralPage *centralPageWidget = new CentralPage("test", this);

    // South Widget //
    southWidget = new QStatusBar(this);


    layout = new BorderLayout;
    layout->addWidget( centralPageWidget, BorderLayout::Center);
    layout->addWidget( southWidget, BorderLayout::South);

    setLayout(layout);
    setWindowTitle(tr("Home Window"));
    setMinimumSize(1000*0.7,618*0.7);

    southWidget->showMessage("Ready...");
}

CentralPage::CentralPage( const QString &expID, QWidget *parent)
    : HomeWindow()
{
    QPushButton *someBtn = new QPushButton(tr("Click me"));
    QHBoxLayout *layout = new QHBoxLayout;
    layout->addWidget( someBtn );
    setLayout( layout );

    connect(someBtn, SIGNAL( clicked() ), this, SLOT( btnSlot()));
}
void CentralPage::btnSlot()
{
    southWidget->showMessage("button clicked...");

}



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