Q_OBJECT, vtables and basic GUI control.

[Diath]

Hello QT Geeks!

I have to create GUI for my application and after re-search I've had to choose between wxWidgets and QT, and my choice was QT.
I've downloaded newest QT Version from http://qt.nokia.com (i.e. 4.6.3), MinGW 5.1.6 and Code::Blocks (Also latest version.) and I'm working on Windows XP Professional Service Pack 3.
I've configured my Code::Blocks using some wiki tutorial (Can't remember where did I find the link so can't post :/).

Basically I need 2 "windows" in 2 classes:
a) Login Window with 2 static texts, 2 text boxes and 3 push buttons.
b) Client window with few tabs, buttons and such.

Here's my code:

main.cpp:

#include <QApplication>
#include "LoginInterface.h"
 
int main(int argc, char *argv[])
{
	QApplication app(argc, argv);
 
	LoginInterface li;
	li.show();
 
	return app.exec();
}

#include <QApplication>
#include "LoginInterface.h"

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

	LoginInterface li;
	li.show();

	return app.exec();
}

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LoginInterface.cpp:

#include <QLabel>
 
#include "LoginInterface.h"
 
LoginInterface::LoginInterface()
{
    QLabel *NameDialog = new QLabel(tr("Name:"));
    NameDialog->show();
}

#include <QLabel>

#include "LoginInterface.h"

LoginInterface::LoginInterface()
{
    QLabel *NameDialog = new QLabel(tr("Name:"));
    NameDialog->show();
}

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LoginInterface.h:

#ifndef LOGININTERFACE_H
#define LOGININTERFACE_H
 
#include <QMainWindow>
 
class LoginInterface : public QMainWindow
{
	Q_OBJECT
	public:
		LoginInterface();
};
 
#endif

#ifndef LOGININTERFACE_H
#define LOGININTERFACE_H

#include <QMainWindow>

class LoginInterface : public QMainWindow
{
	Q_OBJECT
	public:
		LoginInterface();
};

#endif

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As you can see in LoginInterface header file, there's Q_OBJECT variable, but with this variable I'm getting following errors:

obj\LoginInterface.o:LoginInterface.cpp:(.text+0x66): undefined reference to `LoginInterface::staticMetaObject'
obj\LoginInterface.o:LoginInterface.cpp:(.text+0x71): undefined reference to `vtable for LoginInterface'
obj\LoginInterface.o:LoginInterface.cpp:(.text+0x78): undefined reference to `vtable for LoginInterface'
obj\LoginInterface.o:LoginInterface.cpp:(.text+0x1f8): undefined reference to `vtable for LoginInterface'
obj\LoginInterface.o:LoginInterface.cpp:(.text+0x1ff): undefined reference to `vtable for LoginInterface'
obj\LoginInterface.o:LoginInterface.cpp:(.text+0x213): undefined reference to `LoginInterface::staticMetaObject'

obj\LoginInterface.o:LoginInterface.cpp:(.text+0x66): undefined reference to `LoginInterface::staticMetaObject'
obj\LoginInterface.o:LoginInterface.cpp:(.text+0x71): undefined reference to `vtable for LoginInterface'
obj\LoginInterface.o:LoginInterface.cpp:(.text+0x78): undefined reference to `vtable for LoginInterface'
obj\LoginInterface.o:LoginInterface.cpp:(.text+0x1f8): undefined reference to `vtable for LoginInterface'
obj\LoginInterface.o:LoginInterface.cpp:(.text+0x1ff): undefined reference to `vtable for LoginInterface'
obj\LoginInterface.o:LoginInterface.cpp:(.text+0x213): undefined reference to `LoginInterface::staticMetaObject'

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But when I remove that (Yea I know, ugly cheat. :p), everything compiles fine, but GUI comes with separated windows, like on this screen:


Is there any way to fix Q_OBJECT thing and fix windows, so new controls will be CHILDS, not separated windows?

Also I've tried other ready code and C::B threw me error about 'Undefined QThread' or something, do I miss some parts of QT or?

Cheers, Diath.
PS: I hope you'll understand my english, it's kinda bad but i tried to write as proper as I can.

[tbscope]

There are a couple of things not completely correct.

The following code is ok:

#include <QApplication>
#include "LoginInterface.h"
 
int main(int argc, char *argv[])
{
	QApplication app(argc, argv);
 
	LoginInterface li;
	li.show();
 
	return app.exec();
}

#include <QApplication>
#include "LoginInterface.h"
 
int main(int argc, char *argv[])
{
	QApplication app(argc, argv);
 
	LoginInterface li;
	li.show();
 
	return app.exec();
}

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The LoginInterface class isn't.
Try this:

#ifndef LOGININTERFACE_H
#define LOGININTERFACE_H
 
#include <QDialog>
 
class LoginInterface : public QDialog
{
Q_OBJECT
 
public:
    LoginInterface(QWidget *parent = 0, Qt::WindowFlags flags = 0 );
};
 
#endif

#ifndef LOGININTERFACE_H
#define LOGININTERFACE_H
 
#include <QDialog>
 
class LoginInterface : public QDialog
{
Q_OBJECT

public:
    LoginInterface(QWidget *parent = 0, Qt::WindowFlags flags = 0 );
};
 
#endif

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And for the implementation try this:

#include <QLabel>
#include <QHBoxLayout>
 
#include "LoginInterface.h"
 
LoginInterface::LoginInterface(QWidget *parent = 0, Qt::WindowFlags flags = 0) :
    QDialog(parent, flags)
{
    QHBoxLayout *labelLayout = new QHBoxLayout;
 
    QLabel *inputLabel = new QLabel(tr("Name:"));
    QLineEdit *inputText = new QLineEdit;
 
    labelLayout->addWidget(inputLabel);
    labelLayout->addWidget(inputText);
 
    setLayout(labelLayout);
}

#include <QLabel>
#include <QHBoxLayout>
 
#include "LoginInterface.h"
 
LoginInterface::LoginInterface(QWidget *parent = 0, Qt::WindowFlags flags = 0) :
    QDialog(parent, flags)
{
    QHBoxLayout *labelLayout = new QHBoxLayout;

    QLabel *inputLabel = new QLabel(tr("Name:"));
    QLineEdit *inputText = new QLineEdit;

    labelLayout->addWidget(inputLabel);
    labelLayout->addWidget(inputText);

    setLayout(labelLayout);
}

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If you create a widget within the code of another widget, and you don't set the parent of the new widget and then you call show(), you do show this new widget in a new window.

Use layouts. You don't have to explicitly set parents for child widgets as the layout reparents them and setLayout will make the parent widget take control of it.

Edit: and try to clean your project and rebuild it completely.

[Zlatomir]

This is where you need to pass the parent pointer (in your case the "this" pointer):

QLabel *NameDialog = new QLabel(tr("Name:"), this);

QLabel *NameDialog = new QLabel(tr("Name:"), this);

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LE: to late, and incomplete

[Diath]

Thank you both guys for fast answers.

@tbscope:
I did try your code, and did as you wrote in your edit, but C::B threw me new errors:

C:\Documents and Settings\Kamil\Pulpit\The Bloody War\client_launcher\LoginInterface.h:14:7: warning: no newline at end of file
C:\Documents and Settings\Kamil\Pulpit\The Bloody War\client_launcher\LoginInterface.cpp:6: error: default argument given for parameter 1 of `LoginInterface::LoginInterface(QWidget*, Qt::WindowFlags)'
C:\Documents and Settings\Kamil\Pulpit\The Bloody War\client_launcher\LoginInterface.h:11: error: after previous specification in `LoginInterface::LoginInterface(QWidget*, Qt::WindowFlags)'
C:\Documents and Settings\Kamil\Pulpit\The Bloody War\client_launcher\LoginInterface.cpp:6: error: default argument given for parameter 2 of `LoginInterface::LoginInterface(QWidget*, Qt::WindowFlags)'
C:\Documents and Settings\Kamil\Pulpit\The Bloody War\client_launcher\LoginInterface.h:11: error: after previous specification in `LoginInterface::LoginInterface(QWidget*, Qt::WindowFlags)'
C:\Documents and Settings\Kamil\Pulpit\The Bloody War\client_launcher\LoginInterface.cpp: In constructor `LoginInterface::LoginInterface(QWidget*, Qt::WindowFlags)':
C:\Documents and Settings\Kamil\Pulpit\The Bloody War\client_launcher\LoginInterface.cpp:12: error: `QLineEdit' was not declared in this scope
C:\Documents and Settings\Kamil\Pulpit\The Bloody War\client_launcher\LoginInterface.cpp:12: error: `inputText' was not declared in this scope
C:\Documents and Settings\Kamil\Pulpit\The Bloody War\client_launcher\LoginInterface.cpp:12: error: `QLineEdit' is not a type
C:\Documents and Settings\Kamil\Pulpit\The Bloody War\client_launcher\LoginInterface.cpp:12: warning: unused variable 'QLineEdit'

C:\Documents and Settings\Kamil\Pulpit\The Bloody War\client_launcher\LoginInterface.h:14:7: warning: no newline at end of file
C:\Documents and Settings\Kamil\Pulpit\The Bloody War\client_launcher\LoginInterface.cpp:6: error: default argument given for parameter 1 of `LoginInterface::LoginInterface(QWidget*, Qt::WindowFlags)'
C:\Documents and Settings\Kamil\Pulpit\The Bloody War\client_launcher\LoginInterface.h:11: error: after previous specification in `LoginInterface::LoginInterface(QWidget*, Qt::WindowFlags)'
C:\Documents and Settings\Kamil\Pulpit\The Bloody War\client_launcher\LoginInterface.cpp:6: error: default argument given for parameter 2 of `LoginInterface::LoginInterface(QWidget*, Qt::WindowFlags)'
C:\Documents and Settings\Kamil\Pulpit\The Bloody War\client_launcher\LoginInterface.h:11: error: after previous specification in `LoginInterface::LoginInterface(QWidget*, Qt::WindowFlags)'
C:\Documents and Settings\Kamil\Pulpit\The Bloody War\client_launcher\LoginInterface.cpp: In constructor `LoginInterface::LoginInterface(QWidget*, Qt::WindowFlags)':
C:\Documents and Settings\Kamil\Pulpit\The Bloody War\client_launcher\LoginInterface.cpp:12: error: `QLineEdit' was not declared in this scope
C:\Documents and Settings\Kamil\Pulpit\The Bloody War\client_launcher\LoginInterface.cpp:12: error: `inputText' was not declared in this scope
C:\Documents and Settings\Kamil\Pulpit\The Bloody War\client_launcher\LoginInterface.cpp:12: error: `QLineEdit' is not a type
C:\Documents and Settings\Kamil\Pulpit\The Bloody War\client_launcher\LoginInterface.cpp:12: warning: unused variable 'QLineEdit'

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So I did add following code under #include <QLabel>:

#include <QLineEdit>

#include <QLineEdit>

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Now I'm getting only these errors (I assume they're about LoginInterface constructor.):

C:\Documents and Settings\Kamil\Pulpit\The Bloody War\client_launcher\LoginInterface.cpp:7: error: default argument given for parameter 1 of `LoginInterface::LoginInterface(QWidget*, Qt::WindowFlags)'
C:\Documents and Settings\Kamil\Pulpit\The Bloody War\client_launcher\LoginInterface.h:11: error: after previous specification in `LoginInterface::LoginInterface(QWidget*, Qt::WindowFlags)'
C:\Documents and Settings\Kamil\Pulpit\The Bloody War\client_launcher\LoginInterface.cpp:7: error: default argument given for parameter 2 of `LoginInterface::LoginInterface(QWidget*, Qt::WindowFlags)'
C:\Documents and Settings\Kamil\Pulpit\The Bloody War\client_launcher\LoginInterface.h:11: error: after previous specification in `LoginInterface::LoginInterface(QWidget*, Qt::WindowFlags)'

C:\Documents and Settings\Kamil\Pulpit\The Bloody War\client_launcher\LoginInterface.cpp:7: error: default argument given for parameter 1 of `LoginInterface::LoginInterface(QWidget*, Qt::WindowFlags)'
C:\Documents and Settings\Kamil\Pulpit\The Bloody War\client_launcher\LoginInterface.h:11: error: after previous specification in `LoginInterface::LoginInterface(QWidget*, Qt::WindowFlags)'
C:\Documents and Settings\Kamil\Pulpit\The Bloody War\client_launcher\LoginInterface.cpp:7: error: default argument given for parameter 2 of `LoginInterface::LoginInterface(QWidget*, Qt::WindowFlags)'
C:\Documents and Settings\Kamil\Pulpit\The Bloody War\client_launcher\LoginInterface.h:11: error: after previous specification in `LoginInterface::LoginInterface(QWidget*, Qt::WindowFlags)'

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[tbscope]

Yes, sorry, I posted it too quickly.
Indeed, add the qlineedit include
But also:

#include <QLabel>
#include <QHBoxLayout>
 
#include "LoginInterface.h"
 
LoginInterface::LoginInterface(QWidget *parent, Qt::WindowFlags flags) :
    QDialog(parent, flags)
{
    QHBoxLayout *labelLayout = new QHBoxLayout;
 
    QLabel *inputLabel = new QLabel(tr("Name:"));
    QLineEdit *inputText = new QLineEdit;
 
    labelLayout->addWidget(inputLabel);
    labelLayout->addWidget(inputText);
 
    setLayout(labelLayout);
}

#include <QLabel>
#include <QHBoxLayout>
 
#include "LoginInterface.h"
 
LoginInterface::LoginInterface(QWidget *parent, Qt::WindowFlags flags) :
    QDialog(parent, flags)
{
    QHBoxLayout *labelLayout = new QHBoxLayout;
 
    QLabel *inputLabel = new QLabel(tr("Name:"));
    QLineEdit *inputText = new QLineEdit;
 
    labelLayout->addWidget(inputLabel);
    labelLayout->addWidget(inputText);
 
    setLayout(labelLayout);
}

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Remove the two = 0 as in the code above. It's not allowed to add default values in the implementation.

[Diath]

Well, I've removed = 0 in both .cpp and .h files, then I moved to main.cpp and my code looks now like this:

#include <QApplication>
#include "LoginInterface.h"
 
int main(int argc, char *argv[])
{
	QApplication app(argc, argv);
	QWidget *MainWidget = new QWidget();
	LoginInterface *li = new LoginInterface(MainWidget, Qt::Dialog);
	li->show();
 
	return app.exec();
}

#include <QApplication>
#include "LoginInterface.h"

int main(int argc, char *argv[])
{
	QApplication app(argc, argv);
	QWidget *MainWidget = new QWidget();
	LoginInterface *li = new LoginInterface(MainWidget, Qt::Dialog);
	li->show();

	return app.exec();
}

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But again, C::B throws me an errors:

obj\LoginInterface.o:LoginInterface.cpp:(.text+0x6a): undefined reference to `vtable for LoginInterface'
obj\LoginInterface.o:LoginInterface.cpp:(.text+0x71): undefined reference to `vtable for LoginInterface'
obj\LoginInterface.o:LoginInterface.cpp:(.text+0xbe): undefined reference to `LoginInterface::staticMetaObject'
obj\LoginInterface.o:LoginInterface.cpp:(.text+0x31a): undefined reference to `vtable for LoginInterface'
obj\LoginInterface.o:LoginInterface.cpp:(.text+0x321): undefined reference to `vtable for LoginInterface'
obj\LoginInterface.o:LoginInterface.cpp:(.text+0x36e): undefined reference to `LoginInterface::staticMetaObject'

obj\LoginInterface.o:LoginInterface.cpp:(.text+0x6a): undefined reference to `vtable for LoginInterface'
obj\LoginInterface.o:LoginInterface.cpp:(.text+0x71): undefined reference to `vtable for LoginInterface'
obj\LoginInterface.o:LoginInterface.cpp:(.text+0xbe): undefined reference to `LoginInterface::staticMetaObject'
obj\LoginInterface.o:LoginInterface.cpp:(.text+0x31a): undefined reference to `vtable for LoginInterface'
obj\LoginInterface.o:LoginInterface.cpp:(.text+0x321): undefined reference to `vtable for LoginInterface'
obj\LoginInterface.o:LoginInterface.cpp:(.text+0x36e): undefined reference to `LoginInterface::staticMetaObject'

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I guess it's me who's doing something wrong, I really appreciate your help .

[Zlatomir]

Leave the =0 in header file

[Diath]

Still:

obj\LoginInterface.o:LoginInterface.cpp:(.text+0x6a): undefined reference to `vtable for LoginInterface'
obj\LoginInterface.o:LoginInterface.cpp:(.text+0x71): undefined reference to `vtable for LoginInterface'
obj\LoginInterface.o:LoginInterface.cpp:(.text+0xbe): undefined reference to `LoginInterface::staticMetaObject'
obj\LoginInterface.o:LoginInterface.cpp:(.text+0x31a): undefined reference to `vtable for LoginInterface'
obj\LoginInterface.o:LoginInterface.cpp:(.text+0x321): undefined reference to `vtable for LoginInterface'
obj\LoginInterface.o:LoginInterface.cpp:(.text+0x36e): undefined reference to `LoginInterface::staticMetaObject'

obj\LoginInterface.o:LoginInterface.cpp:(.text+0x6a): undefined reference to `vtable for LoginInterface'
obj\LoginInterface.o:LoginInterface.cpp:(.text+0x71): undefined reference to `vtable for LoginInterface'
obj\LoginInterface.o:LoginInterface.cpp:(.text+0xbe): undefined reference to `LoginInterface::staticMetaObject'
obj\LoginInterface.o:LoginInterface.cpp:(.text+0x31a): undefined reference to `vtable for LoginInterface'
obj\LoginInterface.o:LoginInterface.cpp:(.text+0x321): undefined reference to `vtable for LoginInterface'
obj\LoginInterface.o:LoginInterface.cpp:(.text+0x36e): undefined reference to `LoginInterface::staticMetaObject'

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And yes, I did "clean and rebuild" project.

I have to leave for the moment, will take a look here later. I hope someone will help .

[Zlatomir]

Here you have the little project that worksTestTest.zip
LE: exact code that tbscope provided (incuding the two little corrections)

[tbscope]

Does your setup find the meta object compiler?

[Diath]

Here you have the little project that worksTestTest.zip
LE: exact code that tbscope provided (incuding the two little corrections)

Seems like I've installed QT wrong, still throws me an error.

Does your setup find the meta object compiler?

How do I check/fix? (Sorry for dumb questions.)

[ChrisW67]

How does Code::Blocks manage the steps needed to build a Qt program? Is Code::Blocks running your source through Qt moc (look for LoginInterface_moc.cpp) ? Is there a qmake PRO file?

If you have no pressing reason to stick with Code::Blocks then you should consider Qt Creator, which manages many Qt aspects for you.

[Diath]

How does Code::Blocks manage the steps needed to build a Qt program? Is Code::Blocks running your source through Qt moc (look for LoginInterface_moc.cpp) ? Is there a qmake PRO file?

If you have no pressing reason to stick with Code::Blocks then you should consider Qt Creator, which manages many Qt aspects for you.

There's no moc or pro file.

And I'm using C::B only to press damn F9 button, so I can switch to Qt Creator, but what then? Will I have to integrate MinGW or something with it? Is there any guide how to setup it properly?

[Zlatomir]

Qt SDK for Windows has everything ready to run, and the one for Linux need to have g++ and make installed on your system.

[tbscope]

If you download the Qt SDK, it includes everything. Just install it, open Qt Creator and build without problems.

[Diath]

[Diath]

Okay, I don't want to create new thread, so gonna post here.
I have button in LoginInterface class, and after passing click signal to that button I call following function:

void LoginInterface::Run()
{
	// Totalny rozpierdol!
	delete UserLabel;
	delete UserInput;
	delete MainLayout;
 
	// Basic Tab
	BasicWidget = new QWidget;
	BasicLayout = new QGridLayout;
 
	// // Basic Tab - Controls
	UsernameLabel = new QLabel("User:");
	UsernameEdit = new QLineEdit;
	BasicWidget->setLayout(BasicLayout);
 
	// // Basic Tab - Adding widgets
	BasicLayout->addWidget(UsernameLabel);
	BasicLayout->addWidget(UsernameEdit);
 
	// Tabs
	Tabs = new QTabWidget;
	Tabs->addTab(BasicWidget, tr("Basic Info"));
	Tabs->show();
}

void LoginInterface::Run()
{
	// Totalny rozpierdol!
	delete UserLabel;
	delete UserInput;
	delete MainLayout;

	// Basic Tab
	BasicWidget = new QWidget;
	BasicLayout = new QGridLayout;

	// // Basic Tab - Controls
	UsernameLabel = new QLabel("User:");
	UsernameEdit = new QLineEdit;
	BasicWidget->setLayout(BasicLayout);

	// // Basic Tab - Adding widgets
	BasicLayout->addWidget(UsernameLabel);
	BasicLayout->addWidget(UsernameEdit);

	// Tabs
	Tabs = new QTabWidget;
	Tabs->addTab(BasicWidget, tr("Basic Info"));
	Tabs->show();
}

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But tabs comes in separated window, how do I pass parent? ;p

[ChrisW67]

Add the Tabs widget to a layout inside LoginInterface's central widget, or the layout of the window you want the widget to appear in, rather than "Tabs->show()". Exactly how you do that depends on exactly how things are arranged now, and what you want to happen.

[Diath]

Oh, lol. Thank you, solution:

MainLayout->addWidget(Tabs);

MainLayout->addWidget(Tabs);

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+ removing:

delete MainLayout;

delete MainLayout;

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[Diath]

Seems like bad solution, it doesn't fit window (It's like container inside other.), also I haven't "hook" with main window or something so I can't resize it. Any tips?