- Qt 5.5
- Qt Widgets
- Application Example
- mainwindow.cpp Example File
- Qt 5.5.1 Reference Documentation

# mainwindow.cpp Example File

mainwindows/application/mainwindow.cpp

    /****************************************************************************
    **
    ** Copyright (C) 2015 The Qt Company Ltd.
    ** Contact: http://www.qt.io/licensing/
    **
    ** This file is part of the examples of the Qt Toolkit.
    **
    ** $QT_BEGIN_LICENSE:BSD$
    ** You may use this file under the terms of the BSD license as follows:
    **
    ** "Redistribution and use in source and binary forms, with or without
    ** modification, are permitted provided that the following conditions are
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    **   * Redistributions of source code must retain the above copyright
    **     notice, this list of conditions and the following disclaimer.
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    **     notice, this list of conditions and the following disclaimer in
    **     the documentation and/or other materials provided with the
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    **     contributors may be used to endorse or promote products derived
    **     from this software without specific prior written permission.
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    #include <QtWidgets>

    #include "mainwindow.h"

    MainWindow::MainWindow()
    {
        textEdit = new QPlainTextEdit;
        setCentralWidget(textEdit);

        createActions();
        createMenus();
        createToolBars();
        createStatusBar();

        readSettings();

        connect(textEdit->document(), SIGNAL(contentsChanged()),
                this, SLOT(documentWasModified()));

        setCurrentFile("");
        setUnifiedTitleAndToolBarOnMac(true);
    }

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

    void MainWindow::newFile()
    {
        if (maybeSave()) {
            textEdit->clear();
            setCurrentFile("");
        }
    }

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

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

    bool MainWindow::saveAs()
    {
        QFileDialog dialog(this);
        dialog.setWindowModality(Qt::WindowModal);
        dialog.setAcceptMode(QFileDialog::AcceptSave);
        QStringList files;
        if (dialog.exec())
            files = dialog.selectedFiles();
        else
            return false;

        return saveFile(files.at(0));
    }

    void MainWindow::about()
    {
       QMessageBox::about(this, tr("About Application"),
                tr("The <b>Application</b> example demonstrates how to "
                   "write modern GUI applications using Qt, with a menu bar, "
                   "toolbars, and a status bar."));
    }

    void MainWindow::documentWasModified()
    {
        setWindowModified(textEdit->document()->isModified());
    }

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

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

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

        saveAsAct = new QAction(tr("Save &As..."), this);
        saveAsAct->setShortcuts(QKeySequence::SaveAs);
        saveAsAct->setStatusTip(tr("Save the document under a new name"));
        connect(saveAsAct, SIGNAL(triggered()), this, SLOT(saveAs()));

        exitAct = new QAction(tr("E&xit"), this);
        exitAct->setShortcuts(QKeySequence::Quit);
        exitAct->setStatusTip(tr("Exit the application"));
        connect(exitAct, SIGNAL(triggered()), this, SLOT(close()));

        cutAct = new QAction(QIcon(":/images/cut.png"), tr("Cu&t"), this);
        cutAct->setShortcuts(QKeySequence::Cut);
        cutAct->setStatusTip(tr("Cut the current selection's contents to the "
                                "clipboard"));
        connect(cutAct, SIGNAL(triggered()), textEdit, SLOT(cut()));

        copyAct = new QAction(QIcon(":/images/copy.png"), tr("&Copy"), this);
        copyAct->setShortcuts(QKeySequence::Copy);
        copyAct->setStatusTip(tr("Copy the current selection's contents to the "
                                 "clipboard"));
        connect(copyAct, SIGNAL(triggered()), textEdit, SLOT(copy()));

        pasteAct = new QAction(QIcon(":/images/paste.png"), tr("&Paste"), this);
        pasteAct->setShortcuts(QKeySequence::Paste);
        pasteAct->setStatusTip(tr("Paste the clipboard's contents into the current "
                                  "selection"));
        connect(pasteAct, SIGNAL(triggered()), textEdit, SLOT(paste()));

        aboutAct = new QAction(tr("&About"), this);
        aboutAct->setStatusTip(tr("Show the application's About box"));
        connect(aboutAct, SIGNAL(triggered()), this, SLOT(about()));

        aboutQtAct = new QAction(tr("About &Qt"), this);
        aboutQtAct->setStatusTip(tr("Show the Qt library's About box"));
        connect(aboutQtAct, SIGNAL(triggered()), qApp, SLOT(aboutQt()));

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

    void MainWindow::createMenus()
    {
        fileMenu = menuBar()->addMenu(tr("&File"));
        fileMenu->addAction(newAct);
        fileMenu->addAction(openAct);
        fileMenu->addAction(saveAct);
        fileMenu->addAction(saveAsAct);
        fileMenu->addSeparator();
        fileMenu->addAction(exitAct);

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

        menuBar()->addSeparator();

        helpMenu = menuBar()->addMenu(tr("&Help"));
        helpMenu->addAction(aboutAct);
        helpMenu->addAction(aboutQtAct);
    }

    void MainWindow::createToolBars()
    {
        fileToolBar = addToolBar(tr("File"));
        fileToolBar->addAction(newAct);
        fileToolBar->addAction(openAct);
        fileToolBar->addAction(saveAct);

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

    void MainWindow::createStatusBar()
    {
        statusBar()->showMessage(tr("Ready"));
    }

    void MainWindow::readSettings()
    {
        QSettings settings("QtProject", "Application Example");
        QPoint pos = settings.value("pos", QPoint(200, 200)).toPoint();
        QSize size = settings.value("size", QSize(400, 400)).toSize();
        resize(size);
        move(pos);
    }

    void MainWindow::writeSettings()
    {
        QSettings settings("QtProject", "Application Example");
        settings.setValue("pos", pos());
        settings.setValue("size", size());
    }

    bool MainWindow::maybeSave()
    {
        if (textEdit->document()->isModified()) {
            QMessageBox::StandardButton ret;
            ret = QMessageBox::warning(this, tr("Application"),
                         tr("The document has been modified.\n"
                            "Do you want to save your changes?"),
                         QMessageBox::Save | QMessageBox::Discard | QMessageBox::Cancel);
            if (ret == QMessageBox::Save)
                return save();
            else if (ret == QMessageBox::Cancel)
                return false;
        }
        return true;
    }

    void MainWindow::loadFile(const QString &fileName)
    {
        QFile file(fileName);
        if (!file.open(QFile::ReadOnly | QFile::Text)) {
            QMessageBox::warning(this, tr("Application"),
                                 tr("Cannot read file %1:\n%2.")
                                 .arg(fileName)
                                 .arg(file.errorString()));
            return;
        }

        QTextStream in(&file);
    #ifndef QT_NO_CURSOR
        QApplication::setOverrideCursor(Qt::WaitCursor);
    #endif
        textEdit->setPlainText(in.readAll());
    #ifndef QT_NO_CURSOR
        QApplication::restoreOverrideCursor();
    #endif

        setCurrentFile(fileName);
        statusBar()->showMessage(tr("File loaded"), 2000);
    }

    bool MainWindow::saveFile(const QString &fileName)
    {
        QFile file(fileName);
        if (!file.open(QFile::WriteOnly | QFile::Text)) {
            QMessageBox::warning(this, tr("Application"),
                                 tr("Cannot write file %1:\n%2.")
                                 .arg(fileName)
                                 .arg(file.errorString()));
            return false;
        }

        QTextStream out(&file);
    #ifndef QT_NO_CURSOR
        QApplication::setOverrideCursor(Qt::WaitCursor);
    #endif
        out << textEdit->toPlainText();
    #ifndef QT_NO_CURSOR
        QApplication::restoreOverrideCursor();
    #endif

        setCurrentFile(fileName);
        statusBar()->showMessage(tr("File saved"), 2000);
        return true;
    }

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

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

    QString MainWindow::strippedName(const QString &fullFileName)
    {
        return QFileInfo(fullFileName).fileName();
    }