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

# mainwindow.cpp Example File

mainwindows/recentfiles/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:
    **
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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()
    {
        setAttribute(Qt::WA_DeleteOnClose);

        textEdit = new QTextEdit;
        setCentralWidget(textEdit);

        createActions();
        createMenus();
        (void)statusBar();

        setWindowFilePath(QString());
        resize(400, 300);
    }

    void MainWindow::newFile()
    {
        MainWindow *other = new MainWindow;
        other->show();
    }

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

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

    void MainWindow::saveAs()
    {
        QString fileName = QFileDialog::getSaveFileName(this);
        if (fileName.isEmpty())
            return;

        saveFile(fileName);
    }

    void MainWindow::openRecentFile()
    {
        QAction *action = qobject_cast<QAction *>(sender());
        if (action)
            loadFile(action->data().toString());
    }

    void MainWindow::about()
    {
       QMessageBox::about(this, tr("About Recent Files"),
                tr("The <b>Recent Files</b> example demonstrates how to provide a "
                   "recently used file menu in a Qt application."));
    }

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

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

        saveAct = new QAction(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()));

        for (int i = 0; i < MaxRecentFiles; ++i) {
            recentFileActs[i] = new QAction(this);
            recentFileActs[i]->setVisible(false);
            connect(recentFileActs[i], SIGNAL(triggered()),
                    this, SLOT(openRecentFile()));
        }

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

        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()));
    }

    void MainWindow::createMenus()
    {
        fileMenu = menuBar()->addMenu(tr("&File"));
        fileMenu->addAction(newAct);
        fileMenu->addAction(openAct);
        fileMenu->addAction(saveAct);
        fileMenu->addAction(saveAsAct);
        separatorAct = fileMenu->addSeparator();
        for (int i = 0; i < MaxRecentFiles; ++i)
            fileMenu->addAction(recentFileActs[i]);
        fileMenu->addSeparator();
        fileMenu->addAction(exitAct);
        updateRecentFileActions();

        menuBar()->addSeparator();

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

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

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

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

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

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

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

    void MainWindow::setCurrentFile(const QString &fileName)
    {
        curFile = fileName;
        setWindowFilePath(curFile);

        QSettings settings;
        QStringList files = settings.value("recentFileList").toStringList();
        files.removeAll(fileName);
        files.prepend(fileName);
        while (files.size() > MaxRecentFiles)
            files.removeLast();

        settings.setValue("recentFileList", files);

        foreach (QWidget *widget, QApplication::topLevelWidgets()) {
            MainWindow *mainWin = qobject_cast<MainWindow *>(widget);
            if (mainWin)
                mainWin->updateRecentFileActions();
        }
    }

    void MainWindow::updateRecentFileActions()
    {
        QSettings settings;
        QStringList files = settings.value("recentFileList").toStringList();

        int numRecentFiles = qMin(files.size(), (int)MaxRecentFiles);

        for (int i = 0; i < numRecentFiles; ++i) {
            QString text = tr("&%1 %2").arg(i + 1).arg(strippedName(files[i]));
            recentFileActs[i]->setText(text);
            recentFileActs[i]->setData(files[i]);
            recentFileActs[i]->setVisible(true);
        }
        for (int j = numRecentFiles; j < MaxRecentFiles; ++j)
            recentFileActs[j]->setVisible(false);

        separatorAct->setVisible(numRecentFiles > 0);
    }

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