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# mainwindow.cpp Example File
mainwindows/recentfiles/mainwindow.cpp

        #include <QtGui>

        #include "mainwindow.h"

        MainWindow::MainWindow()
        {
            setAttribute(Qt::WA_DeleteOnClose);

            textEdit = new QTextEdit(this);
            setCentralWidget(textEdit);

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

            setWindowTitle(tr("Recent Files"));
            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;

            if (QFile::exists(fileName)) {
                int ret = QMessageBox::warning(this, tr("Recent Files"),
                             tr("File %1 already exists.\n"
                                "Do you want to overwrite it?")
                             .arg(QDir::convertSeparators(fileName)),
                             QMessageBox::Yes | QMessageBox::Default,
                             QMessageBox::No | QMessageBox::Escape);
                if (ret == QMessageBox::No)
                    return;
            }
            saveFile(fileName);
        }

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

        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->setShortcut(tr("Ctrl+N"));
            newAct->setStatusTip(tr("Create a new file"));
            connect(newAct, SIGNAL(triggered()), this, SLOT(newFile()));

            openAct = new QAction(tr("&Open..."), this);
            openAct->setShortcut(tr("Ctrl+O"));
            openAct->setStatusTip(tr("Open an existing file"));
            connect(openAct, SIGNAL(triggered()), this, SLOT(open()));

            saveAct = new QAction(tr("&Save"), this);
            saveAct->setShortcut(tr("Ctrl+S"));
            saveAct->setStatusTip(tr("Save the document to disk"));
            connect(saveAct, SIGNAL(triggered()), this, SLOT(save()));

            saveAsAct = new QAction(tr("Save &As..."), this);
            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("&Close"), this);
            exitAct->setShortcut(tr("Ctrl+W"));
            exitAct->setStatusTip(tr("Close this window"));
            connect(exitAct, SIGNAL(triggered()), this, SLOT(close()));

            exitAct = new QAction(tr("E&xit"), this);
            exitAct->setShortcut(tr("Ctrl+Q"));
            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;
            if (curFile.isEmpty())
                setWindowTitle(tr("Recent Files"));
            else
                setWindowTitle(tr("%1 - %2").arg(strippedName(curFile))
                                            .arg(tr("Recent Files")));

            QSettings settings("doc.trolltech.com", "Recent Files");
            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("doc.trolltech.com", "Recent Files");
            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]->setIconText(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();
        }