Why am I not getting a display in my Qt Widget? - c++

Question

When I run it it will just finish right away and not show anything. I can't find anything wrong w/it and no one on #qt could either. I've got other apps working fine so I'm not sure. It's got something to do with the createForm call, if I omit that call in the constructor I do get a default QWidget displayed.
captchit.pro
#-------------------------------------------------
#
# Project created by QtCreator 2011-02-26T20:58:23
#
#-------------------------------------------------
QT += core gui network
TARGET = captchit
TEMPLATE = app
SOURCES += main.cpp\
widget.cpp
HEADERS += widget.h
main.cpp
#include "QtGui/QApplication"
#include "widget.h"
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
Widget mainWidget;
mainWidget.show();
return a.exec();
}
widget.h
#ifndef WIDGET_H
#define WIDGET_H
#include <QWidget>
class QPixmap;
class QLabel;
class QLineEdit;
class QPushButton;
class Widget : public QWidget
{
Q_OBJECT
public:
Widget(QWidget *parent = 0);
private slots:
void on_refreshButton_pressed();
void on_submitButton_pressed();
void on_closeButton_pressed();
private:
QPixmap captchaImage;
QLabel *imageLabel;
QLabel *statusLabel;
QLineEdit *captchaLineEdit;
QPushButton *submitButton;
QPushButton *refreshButton;
QPushButton *closeButton;
void createForm();
void createActions();
void getCaptcha();
void submitCaptcha();
};
endif // WIDGET_H
widget.cpp
#include "widget.h"
#include "QtNetwork/QtNetwork"
#include "QtGui"
void Widget::on_refreshButton_pressed()
{
;
}
void Widget::on_submitButton_pressed()
{
;
}
void Widget::on_closeButton_pressed()
{
;
}
// Create UI Components
void Widget::createForm()
{
// Create Main Layout
QVBoxLayout *mainLayout = new QVBoxLayout(this);
// // set captcha pixmap to imageLabel for displaying
// imageLabel->setPixmap(captchaImage);
// Create Buttons
QVBoxLayout *buttonLayout = new QVBoxLayout();
submitButton->setText("Submit");
refreshButton->setText("Refresh");
closeButton->setText("Close");
buttonLayout->addWidget(submitButton);
buttonLayout->addWidget(refreshButton);
buttonLayout->addWidget(closeButton);
// Complete Layouts
// lineEdit & submitStatus
QVBoxLayout *lineEditLayout = new QVBoxLayout();
lineEditLayout->addStretch();
lineEditLayout->addWidget(statusLabel);
lineEditLayout->addWidget(captchaLineEdit);
lineEditLayout->addStretch();
// Create Bottom Layout
QHBoxLayout *bottomLayout = new QHBoxLayout();
bottomLayout->addLayout(lineEditLayout);
bottomLayout->addLayout(buttonLayout);
// Add to mainLayout
// mainLayout->addWidget(imageLabel);
mainLayout->addLayout(bottomLayout);
setLayout(mainLayout);
}
// Bind Slots and Signals
void Widget::createActions()
{
;
}
void Widget::getCaptcha()
{
;
}
void Widget::submitCaptcha()
{
;
}
Widget::Widget(QWidget *parent) :
QWidget(parent)
{
createForm();
// createActions();
}

Answer 1

You need to initialize your private class members, probably in your constructor, before you use them.
Widget::Widget(QWidget* parent) :
QWidget(parent)
{
captchaImage = new QPixmap;
imageLabel = new QLabel(this);
statusLabel = new QLabel(this);
captchaLineEdit = new QLineEdit(this);
submitButton = new QPushButton(this);
refreshButton = new QPushButton(this);
closeButton = new QPushButton(this);
createForm();
// createActions();
}
Also note that QPixmap does not derive from QObject, so you'll have to delete it manually. It may be better to remove the QPixmap *captchaImage member from your class and use temporary QPixmap objects in your code.

Answer 2

Oops, it was because I forgot to initialize all of my components, herp derp.