New to QT, problem displaying main window...

[McCall]

Hi Folks!

Hopefully someone can help me with this newbie problem...

I am fairly new to Qt, and I have been using MiniGW, QDevelop, Qt Designer and Qt 4.3 under WindowsXP to try and build a "Playground" applciation that I can add things to while I learn Qt. I haven't really used Qt before, but I have used various C++ API's, most notibly the BeAPI from BeOS and Haiku. I also haven't programmed for a few years, so I am a little unsure if my problem is not knowing how to use Qt, or me forgetting how to program C++ period

I expect my application to show a QMainWindow that will stay on the screen until I press the [x] button, at this point it will close. What I am getting is a Window that flashes on the screen and closes straight away, leaving a process in the Windows process list (I think this is because I am not deleting my new in the relevent destructor)

I have 3 source files, 3 header files and a .UI file. The .UI file contains a Window with a QMainWIndow object called PlaygroundWindowGUI. If needed, I can send a zip file of my folder to anyone that would like to help.

Playground.h:

#ifndef __MAIN_H__
#define __MAIN_H__

// place your code here

#endif // __MAIN_H__

Playground.cpp:

#include <stdio.h>
#include "Playground.h"
#include "PlaygroundApplication.h"

int main(int argc, char *argv[])
{// Main

printf ("Entering main...\n");
PlaygroundApplication Playground(argc, argv);

return Playground.exec();

}// Main

PlaygroundApplication.h:

#ifndef __PLAYGROUNDAPPLICATION_H__
#define __PLAYGROUNDAPPLICATION_H__

#include <QApplication>

class PlaygroundApplication : public QApplication
{
public:
PlaygroundApplication(int argc, char *argv[]);

};

#endif // __PLAYGROUNDAPPLICATION_H__

PlaygroundApplication.cpp:

#include "PlaygroundApplication.h"
#include "PlaygroundWindow.h"

PlaygroundApplication::PlaygroundApplication(int argc, char *argv[]):QApplication(argc, argv)
{

PlaygroundWindow thisPlaygroundWindow;
thisPlaygroundWindow.connect( &thisPlaygroundWindow, SIGNAL( lastWindowClosed() ), &thisPlaygroundWindow, SLOT( quit() ) );
thisPlaygroundWindow.show();

}

PlaygroundWindow.h:

#ifndef __PLAYGROUNDWINDOW_H__
#define __PLAYGROUNDWINDOW_H__

#include "ui_playgroundwindowgui.h"

class PlaygroundWindow : public QMainWindow, public Ui::PlaygroundWindowGUI
{
Q_OBJECT
public:
PlaygroundWindow( QWidget * parent = 0, Qt::WFlags f = 0 );
private slots:
};

#endif // __PLAYGROUNDWINDOW_H__

PlaygroundWindow.cpp:

#include "PlaygroundWindow.h"

PlaygroundWindow::PlaygroundWindow( QWidget * parent, Qt::WFlags f)
: QMainWindow(parent, f)
{
setupUi(this);

}

Can someone please help me work out why this isn't displaying like I expect?

Thanks,

Andrew McCall.

[gri]

PlaygroundWindow thisPlaygroundWindow;
thisPlaygroundWindow.connect( &thisPlaygroundWindow, SIGNAL( lastWindowClosed() ), &thisPlaygroundWindow, SLOT( quit() ) );
thisPlaygroundWindow.show();

PlaygroundWindow thisPlaygroundWindow;
thisPlaygroundWindow.connect( &thisPlaygroundWindow, SIGNAL( lastWindowClosed() ), &thisPlaygroundWindow, SLOT( quit() ) );
thisPlaygroundWindow.show();

To copy to clipboard, switch view to plain text mode 

You create the MainWindow on the stack! It will be closed when the PlaygroundApplication constructor ends. Create your MainWindow with new or do it in the main()-function on the stack.

[McCall]

Thanks for the quick reply!

I have move the creation of the window from the stack, but its still not working. One thing I have noticed is that the printf isn't showing any output either, which I am 99.999% sure should be showing!

Thanks,

Andrew McCall

[gri]

You may take this as example

int main(int argc, char* argv[])
{
  QApplication app(argc, argv);
 
  QMainWindow wnd;
  wnd.show();
  app.setActiveWindow(&wnd);
 
  int ret = app.exec();
 
  // cleanup whatever
 
  return ret;
}

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

  QMainWindow wnd;
  wnd.show();
  app.setActiveWindow(&wnd);

  int ret = app.exec();

  // cleanup whatever

  return ret;
}

To copy to clipboard, switch view to plain text mode 

[McCall]

I think its QDevelop thats causing problems.

If I use qmake -project, qmake, make from the command line my application works.