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

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     #include <QtGui>

     #include "mainwindow.h"

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

         textEdit = new QTextEdit;
         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;

         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->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("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("Trolltech", "Recent Files Example");
         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("Trolltech", "Recent Files Example");
         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();
     }