[SOLVED] App crashes when closing; some objects not closed? MWE

[newe12]

Hi!

My app compiles and works fine, but crashes when i close it.

I have read about this issue in the forum. Some people had solved this problem after they have removed all objects that they allocated on the heap which already had a QObject parent, but they had set them additionally to: "delete somewidget;" before.

I just have:

MainWindow::~MainWindow()
{
    delete mainWindow;
}

to delete the mainWindow.

So I guess, I am missing some objects which I should close too? Or is it another issue?

I have produced a minimal working example:
mainwindow.h

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>


class QTabWidget;
class QWidget;
class QLabel;
class QGroupBox;
class QLineEdit;
class QPushButton;
class QRadioButton;
class QHBoxLayout;
class QFormLayout;
class QDoubleValidator;
class QPalette;



class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    explicit MainWindow(QWidget *parent = 0);
    ~MainWindow();

private slots:
    void startfile();
    void tabcalc();

private:
    void setCurrentIndex();

    QMainWindow *mainWindow;
    QTabWidget *tabWidget;
};





class WelcomeTab : public QWidget
{
    Q_OBJECT
public:
    WelcomeTab(QWidget *parent = 0);
};



class TabCalc : public QWidget
{
    Q_OBJECT
public:
    TabCalc(QWidget *parent = 0);

private slots:
    void calculate();

private:
    QGroupBox *method();
    QGroupBox *input();
    QGroupBox *output();
    QGroupBox *calc();
    QRadioButton *radio1;
    QRadioButton *radio2;
    QLineEdit *inputnumber;
    QLineEdit *output;
};

#endif // MAINWINDOW_H

main.cpp

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

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    MainWindow w;
    w.show();

    return a.exec();
}

mainwindow.cpp

#include "mainwindow.h"
#include <QtGui>
#include <QObject>
#include <cmath>
#include <QPalette>
#include <QLabel>
#include <QHBoxLayout>
#include <QGroupBox>
#include <QRadioButton>
#include <QLineEdit>
#include <QPushButton>
#include <QFormLayout>
#include <QDoubleValidator>
#include <QPalette>


MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent)
{
    tabWidget = new QTabWidget;
    tabWidget->addTab(new WelcomeTab(), tr("Welcome"));
    tabWidget->addTab(new TabCalc(), tr("Calculate"));
    setCentralWidget(tabWidget);

    setWindowTitle(tr("Calculate A or B"));
    setMinimumSize(100, 100);
}


WelcomeTab::WelcomeTab(QWidget *parent)
    : QWidget(parent)
{
    QLabel *welcomeLabel = new QLabel
                (tr("Welcome"));

    QVBoxLayout *mainLayout = new QVBoxLayout;
    mainLayout->addWidget(welcomeLabel);
    setLayout(mainLayout);
}

void MainWindow::startfile()
{
    tabWidget->setCurrentIndex(0);
}


TabCalc::TabCalc(QWidget *parent)
    : QWidget(parent)
{
    QGridLayout *grid = new QGridLayout;
    grid->addWidget(method(), 0, 0);
    grid->addWidget(input(), 0, 1);
    grid->addWidget(output(), 0, 2);
    grid->addWidget(calc(), 0, 3);
    setLayout(grid);
}

QGroupBox *TabCalc::method()
{
    QGroupBox *groupBox = new QGroupBox(tr("Method"));
    radio1 = new QRadioButton(tr("Choice A"));
    radio2 = new QRadioButton(tr("Choice B"));

    QVBoxLayout *vbox = new QVBoxLayout;
     vbox->addWidget(radio1);
     vbox->addWidget(radio2);
     vbox->addStretch(1);
     groupBox->setLayout(vbox);
     return groupBox;
}

QGroupBox *TabCalc::input()
{
    QGroupBox *groupBox = new QGroupBox(tr("Input"));
    inputnumber = new QLineEdit;

    QFormLayout *formLayout = new QFormLayout;
      formLayout->addRow(tr("Insert a number [-10;10]"), inputnumber);
      groupBox->setLayout(formLayout);

      QValidator *validator = new QDoubleValidator(-10, 10, 10, this);
      inputnumber->setValidator(validator);
      return groupBox;
}

QGroupBox *TabCalc::output()
{
    QGroupBox *groupBox = new QGroupBox(tr("Output"));
    QLabel *label = new QLabel(tr("A or B"));
    output = new QLineEdit;

    QFormLayout *formLayout = new QFormLayout;
      formLayout->addRow(label);
      formLayout->addRow(tr("Result:"), output);
      groupBox->setLayout(formLayout);
      return groupBox;
}

QGroupBox *TabCalc::calc()
{
    QGroupBox *groupBox = new QGroupBox(tr("Calculate"));
    QPushButton *pushButton = new QPushButton(tr("Calculate"));

    QVBoxLayout *vbox = new QVBoxLayout;
     vbox->addWidget(pushButton);
     vbox->addStretch(1);
     groupBox->setLayout(vbox);
     connect(pushButton, SIGNAL(clicked()),this, SLOT(calculate()));
     return groupBox;
}

void TabCalc::calculate()
{
    double result;
    bool ok;
    double A=10;
    double B=20;
    double insertedNumber = inputnumber->text().toDouble(&ok);

if(radio1->isChecked())
    {
       result = insertedNumber+A;
       QString resultString = "";
       output->setText(resultString.setNum(result));
    }
    else if(radio2->isChecked())
    {
       result = insertedNumber+B;
       QString resultString = "";
       output->setText(resultString.setNum(result));
    }
    else
    {
       result = 0;
       output->setText("Choose A or B");
    }

}


void MainWindow::tabcalc()
{
   tabWidget->setCurrentIndex(1);
}

MainWindow::~MainWindow()
{
    delete mainWindow;
}    

Please let me know, if you see the problem!

[SGaist]

Hi,

AFAICS, you don't use nor initialize that mainWindow variable so technically you are trying to delete something that doesn't exist

[newe12]

@SGaist, he man, that's great!

Now it works!