Question

Ok. I know I am posting way too much code, but the error is a programmers nightmare.(The segmentation fault)
This is my first application and has assisted by the Qt creator tutorial. Please help.

the notepad.h file:

#ifndef NOTEPAD_H
#define NOTEPAD_H

#include <QMainWindow>
#include <QPlainTextEdit>


class Notepad : public QMainWindow
{
    Q_OBJECT

public:
    Notepad();

protected:
    void closeEvent(QCloseEvent *closeEvent);

private slots:
    void open();
    bool save();
    bool saveAs();
    void newFile();
    void documentWasModified();

private:
    QPlainTextEdit *textField;
    QString curFile;

    QMenu *fileMenu;
    QMenu *editMenu;
    QMenu *helpMenu;

    QToolBar *fileToolBar;
    QToolBar *editToolBar;

    QAction *newAct;
    QAction *loadAct;
    QAction *saveAct;
    QAction *saveAsAct;
    QAction *copyAct;
    QAction *pasteAct;
    QAction *cutAct;
    QAction *exitAct;

    void createMenu();
    void showStatusBar();
    bool maybeSave();
    bool saveFile(const QString &fileName);
    void loadFile(const QString &fileName);
    void setCurrentFile(const QString &fileName);
    void createActions();
    void createToolBars();
    QString strippedName(const QString &fullFileName);

};

#endif

The notepad.cpp file:

#include <QtGui>
#include <QMainWindow>
#include "notepad.h"

Notepad::Notepad()
{
    textField = new QPlainTextEdit;
    setCentralWidget(textField);
    setWindowTitle(tr("The building of a notepad...."));
    createActions();
    createMenu();
    createToolBars();
    showStatusBar();

    connect(textField->document(),SIGNAL(contentsChanged()),this,SLOT(documentWasModified()));
    setCurrentFile("");
    setUnifiedTitleAndToolBarOnMac(true);
}

void Notepad::createActions()
{
    newAct = new QAction(QIcon(":/images/new_File.png"),tr("&New"),this);
    newAct->setShortcuts(QKeySequence::New);
    newAct->setStatusTip("Create A new File!");
    connect(newAct,SIGNAL(triggered()),this,SLOT(newFile()));

    loadAct = new QAction(QIcon(":/images/open_File.gif"),tr("&Load"),this);
    loadAct->setShortcuts(QKeySequence::Open);
    loadAct->setStatusTip("Open an existing file!");
    connect(loadAct,SIGNAL(triggered()),this,SLOT(open()));

    saveAct = new QAction(QIcon(":/images/save_File.png"),tr("&Save"),this);
    saveAct->setShortcuts(QKeySequence::Save);
    saveAct->setStatusTip("Save the file!");
    connect(saveAct,SIGNAL(triggered()),this,SLOT(save()));

    copyAct = new QAction(QIcon(":/images/copy.png"),tr("&Copy"),this);
    saveAsAct->setShortcuts(QKeySequence::Copy);
    saveAsAct->setStatusTip("Copy!");
    connect(saveAsAct,SIGNAL(triggered()),this,SLOT(copy()));

    saveAsAct = new QAction(QIcon(":/images/save_As.png"),tr("&Save As"),this);
    saveAsAct->setShortcuts(QKeySequence::SaveAs);
    saveAsAct->setStatusTip("Save As!");
    connect(saveAsAct,SIGNAL(triggered()),this,SLOT(saveAs())); 

    exitAct = new QAction(QIcon(":/images/exit.png"),tr("&Exit"),this);
    exitAct->setShortcuts(QKeySequence::Close);
    exitAct->setStatusTip("Exit!");
    connect(exitAct,SIGNAL(triggered()),this,SLOT(close()));

    pasteAct = new QAction(QIcon(":/images/paste.gif"),tr("&Paste"),this);
    pasteAct->setShortcuts(QKeySequence::Paste);
    pasteAct->setStatusTip("Paste Text!");
    connect(pasteAct,SIGNAL(triggered()),textField,SLOT(paste()));  

    cutAct = new QAction(QIcon(":/images/cut.png"),tr("&Cut"),this);
    cutAct->setShortcuts(QKeySequence::Cut);
    cutAct->setStatusTip("Cut Text!");
    connect(cutAct,SIGNAL(triggered()),textField,SLOT(cut()));

    copyAct = new QAction(QIcon(":/images/copy.copy"),tr("&Copy"),this);
    copyAct->setShortcuts(QKeySequence::Copy);
    copyAct->setStatusTip("copy Text!");
    connect(copyAct,SIGNAL(triggered()),textField,SLOT(copy()));    

    copyAct->setEnabled(false);
    cutAct->setEnabled(false);
    connect(textField,SIGNAL(copyAvailable(bool)),copyAct,SLOT(setEnabled(bool)));
    connect(textField,SIGNAL(copyAvailable(bool)),cutAct,SLOT(setEnabled(bool)));

}

void Notepad::createMenu()
{
    fileMenu = menuBar()->addMenu(tr("&File"));
    fileMenu->addAction(newAct);
    fileMenu->addAction(loadAct);
    fileMenu->addAction(saveAct);
    fileMenu->addAction(saveAsAct);
    fileMenu->addAction(exitAct);

    editMenu = menuBar()->addMenu(tr("&Edit"));
    editMenu->addAction(cutAct);
    editMenu->addAction(copyAct);
    editMenu->addAction(pasteAct);

    menuBar()->addSeparator();
    helpMenu = menuBar()->addMenu(tr("&Help"));
}

void Notepad::createToolBars()
{
    fileToolBar = addToolBar(tr("File"));
    fileToolBar->addAction(newAct);
    fileToolBar->addAction(loadAct);
    fileToolBar->addAction(saveAct);
    fileToolBar->addAction(saveAsAct);

    editToolBar = addToolBar(tr("Edit"));
    editToolBar->addAction(cutAct);
    editToolBar->addAction(copyAct);
    editToolBar->addAction(pasteAct);


}

void Notepad::showStatusBar()
{
    statusBar()->showMessage(tr("Ready!"));
}

void Notepad::closeEvent(QCloseEvent *event)
{
    if(maybeSave())
        event->accept();
    else
        event->ignore();
}

void Notepad::documentWasModified()
{
    setWindowModified(textField->document()->isModified());
}

bool Notepad::saveAs()
{
    QString fileName = QFileDialog::getSaveFileName(this);
    if(fileName.isEmpty())
        return false;
    return saveFile(fileName);
}

bool Notepad::save()
{
    if(curFile.isEmpty())
        return saveAs();
    else
        return saveFile(curFile);
}

void Notepad::open()
{
    if(maybeSave())
    {
        QString fileName = QFileDialog::getOpenFileName(this);
        if(!fileName.isEmpty())
            loadFile(fileName);
    }

}

void Notepad::newFile()
{
    if(maybeSave())
        {
            textField->clear();
            setCurrentFile("");
        }

}

bool Notepad::maybeSave()
{
    if(textField->document()->isModified())
        {
            QMessageBox::StandardButton ret;
            ret = QMessageBox::warning(this,
                                       tr("Warning!"),
                                       tr("Do you want to save the changes?"),
                                       QMessageBox::Save | QMessageBox::Discard | QMessageBox::Cancel
                                       );
            if(ret==QMessageBox::Cancel)
                return false;
            if(ret==QMessageBox::Save)
                return save();
        }
    return true;
}

bool Notepad::saveFile(const QString &fileName)
{
    QFile file(fileName);
    if(!file.open(QFile::WriteOnly | QFile::Text))
        {
            QMessageBox::warning(this,
                                 tr("Error!"),
                                 tr("%1 file cannot be saved.\nError:").arg(fileName).arg(file.errorString())
                                 );
            return false;
        }
    QTextStream out(&file);
    #ifndef QT_NO_CURSOR
    QApplication::setOverrideCursor(Qt::WaitCursor);
    #endif

    out << textField->toPlainText(); 

    #ifndef QT_NO_CURSOR
    QApplication::restoreOverrideCursor();
    #endif

    setCurrentFile(fileName);
    statusBar()->showMessage(tr("File Saved.:)"),3000);
    return true;
}

void Notepad::loadFile(const QString &fileName)
{
    QFile file(fileName);
    if(!file.open(QFile::ReadOnly | QFile::Text))
        {
            QMessageBox::warning(this,
                                 tr("error"),
                                 tr("error loading %1 file.\nError:%2").arg(fileName).arg(file.errorString())
                                 );
            return;
        }
    QTextStream in(&file);

    #ifndef QT_NO_CURSOR
    QApplication::setOverrideCursor(Qt::WaitCursor);
    #endif

    textField->setPlainText(in.readAll());

    #ifndef QT_NO_CURSOR
    QApplication::restoreOverrideCursor();
    #endif

    setCurrentFile(fileName);
    statusBar()->showMessage(tr("File Loaded!"),3000);
}

void Notepad::setCurrentFile(const QString &fileName)
{
    QString curFile = fileName;
    textField->document()->setModified(false);
    setWindowModified(false);

    QString shownName = curFile;
    if(curFile.isEmpty())
        shownName = "untitled.txt";

    setWindowFilePath(shownName);
}

QString Notepad::strippedName(const QString &fullFilename)
{
    return QFileInfo(fullFilename).fileName();
}

The main.cpp:

#include <QApplication>
#include <QtGui>
#include "notepad.h"

    int main(int argc, char **argv)
    {
        //Q_INIT_RESOURCE(application);

        QApplication app(argc, argv);
        //app.setStyle("motif");                          //possible styles: windows,plastique,cde,motif etc.
        app.setOrganizationName("Trolltech");
        app.setApplicationName("Application Example");
        Notepad mainWin;
    #if defined(Q_OS_SYMBIAN)
        mainWin.showMaximized();
    #else
        mainWin.show();
    #endif

        return app.exec();
    }

Answer 1

Debugger is your friend. Learn to use it.

There is a copy-paste error:

copyAct = new QAction(QIcon(":/images/copy.png"),tr("&Copy"),this);
saveAsAct->setShortcuts(QKeySequence::Copy);
saveAsAct->setStatusTip("Copy!");
connect(saveAsAct,SIGNAL(triggered()),this,SLOT(copy()));

this should be:

copyAct = new QAction(QIcon(":/images/copy.png"),tr("&Copy"),this);
copyAct->setShortcuts(QKeySequence::Copy);
copyAct->setStatusTip("Copy!");
connect(copyAct,SIGNAL(triggered()),this,SLOT(copy()));

You were using an undefined pointer. It is not a nightmare a debugger cannot handle.