QT connect crash using signal accepted - c++

Question

I have a problem with my Qt code. I wanted to write an program which are taking a coordinates of point and then that point is drawing in point with that coordinates. My program doesn't have any errors or warnings when i built it but it's crashing at start(MainWindow doesn't show). This is my code:
main.cpp
#include < QApplication >
#include "mainwindow.h"
int main(int argc, char *argv[])
{
QApplication app(argc, argv);
MainWindow win;
win.show();
return app.exec();
}
mainwindow.h
#ifndef MAINWINDOW_H
#define MAINWINDOW_H
#include <QMainWindow>
#include <QWidget>
#include <QAction>
#include <QToolBar>
#include <QTextCodec>
#include <QObject>
#include <QDialog>
#include <QLineEdit>
#include <QPushButton>
#include <QString>
#include "addpoint.h"
class MainWindow: public QMainWindow
{
Q_OBJECT
private:
QToolBar *AddToolbar;
QAction *AddPointAction;
AddPoint *AddPointDialog;
QLineEdit *x;
public:
MainWindow();
void createToolbar();
void createActionAdd();
signals:
public slots:
void PointClicked();
void DialogAccepted();
};
#endif // MAINWINDOW_H
mainwindow.cpp
#include "mainwindow.h"
MainWindow::MainWindow()
{
QTextCodec::setCodecForLocale(QTextCodec::codecForName("UTF-8"));
createActionAdd();
createToolbar();
connect(AddPointAction, SIGNAL(triggered(bool)), this, SLOT(PointClicked()));
connect(AddPointDialog, SIGNAL(accepted()), this, SLOT(DialogAccepted()));
setMinimumSize(480, 320);
}
/**/
void MainWindow::createToolbar()
{
AddToolbar = new QToolBar;
AddToolbar->addAction(AddPointAction);
addToolBar(AddToolbar);
}
/**/
void MainWindow::createActionAdd()
{
AddPointAction = new QAction("Add Road", this);
x = new QLineEdit(this);
x->setFixedSize(100, 30);
x->move(100, 100);
}
/**/
void MainWindow::PointClicked()
{
AddPointDialog = new AddPoint(this);
AddPointDialog->setModal(true);
AddPointDialog->exec();
}
/**/
void MainWindow::DialogAccepted()
{
x->setText("abc");
}
addpoint.h
#ifndef ADDPOINT_H
#define ADDPOINT_H
#include <QWidget>
#include <QTextCodec>
#include <QDialog>
#include <QObject>
#include <QLabel>
#include <QLineEdit>
#include <QPushButton>
#include <QString>
class AddPoint : public QDialog
{
Q_OBJECT
private:
QLabel *XpointL;
QLineEdit *XPoint;
QPushButton *OKButton;
public:
AddPoint(QWidget *parent);
void createButton();
signals:
public slots:
};
#endif // ADDPOINT_H
addpoint.cpp
#include "addpoint.h"
AddPoint::AddPoint(QWidget *parent) :QDialog(parent)
{
QTextCodec::setCodecForLocale(QTextCodec::codecForName("UTF-8"));
createButton();
connect(OKButton, SIGNAL(clicked(bool)), this, SLOT(accept()));
setMinimumSize(320, 240);
}
/**/
void AddPoint::createButton()
{
XpointL = new QLabel("Point X:", this);
XpointL->setFixedSize(100, 30);
XpointL->move(10, 10);
XPoint = new QLineEdit(this);
XPoint->setFixedSize(180, 30);
XPoint->move(120, 10);
OKButton = new QPushButton("OK", this);
OKButton->setFixedSize(100, 30);
OKButton->move(200, 150);
}
After running the program i see in aplication output lap:
"The program has unexpectedly finished."
"C:\QT\build-xxx-Desktop_Qt_5_4_2_MSVC2013_64bit-Debug\debug\xx.exe crashed"
I note that i made some experiments with this code and i saw that i have problem with signal accpeted() at mainwindow.cpp. I don't know what can i do with this problem. I hope you will help me.

Answer 1

AddPointDialog is uninitialized pointer, it does not yet point to valid AddPoint in MainWindow's constructor. You cannot call connect on that. Its value will change later, when you do AddPointDialog = new AddPoint(this); and only then will you be able to call connect.
Simply, you should move your connect call to void MainWindow::PointClicked() after you've initialized your pointer. I'd also make AddPointDialog local to that function and store it on the stack (you don't use it anywhere else and you're leaking memory).
The code would be:
void MainWindow::PointClicked()
{
AddPoint AddPointDialog(this);
AddPointDialog.setModal(true);
connect(&AddPointDialog, SIGNAL(accepted()), this, SLOT(DialogAccepted()));
AddPointDialog.exec();
}