Qt 文字編輯器實作（下）：選單、工具列、狀態列、檔案操作與設定持久化

建立選單列

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);

    formMenu = menuBar()->addMenu(tr("&Form"));
    formMenu->addAction(automaticAct);
    formMenu->addAction(typefaceAct);

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

建立工具列

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);
}

狀態列初始化

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

設定持久化（QSettings）

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

檔案操作核心邏輯

maybeSave() - 關閉前確認儲存

bool MainWindow::maybeSave() {
    if (textEdit->document()->isModified()) {
        int ret = QMessageBox::warning(this, tr("Application"),
            tr("The document has been modified.\nDo you want to save your changes?"),
            QMessageBox::Yes | QMessageBox::Default,
            QMessageBox::No,
            QMessageBox::Cancel | QMessageBox::Escape);
        if (ret == QMessageBox::Yes) return save();
        else if (ret == QMessageBox::Cancel) return false;
    }
    return true;
}

loadFile() - 載入檔案

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);
    QApplication::setOverrideCursor(Qt::WaitCursor);
    textEdit->setPlainText(in.readAll());
    QApplication::restoreOverrideCursor();
    setCurrentFile(fileName);
    statusBar()->showMessage(tr("File loaded"), 2000);
}

saveFile() - 儲存檔案

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);
    QApplication::setOverrideCursor(Qt::WaitCursor);
    out << textEdit->toPlainText();
    QApplication::restoreOverrideCursor();
    setCurrentFile(fileName);
    statusBar()->showMessage(tr("File saved"), 2000);
    return true;
}

目前檔案狀態管理

void MainWindow::setCurrentFile(const QString &fileName) {
    curFile = fileName;
    textEdit->document()->setModified(false);
    setWindowModified(false);
    QString shownName = curFile.isEmpty() ? "untitled.txt" : strippedName(curFile);
    setWindowTitle(tr("%1[*] - %2").arg(shownName).arg(tr("Application")));
}

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

主程式進入點與資源檔

int main(int argc, char *argv[]) {
    Q_INIT_RESOURCE(application);
    QApplication app(argc, argv);
    MainWindow mainWin;
    mainWin.show();
    return app.exec();
}

資源檔 application.qrc 需在 .pro 加入 RESOURCES = application.qrc：

<RCC>
  <qresource>
    <file>images/copy.png</file>
    <file>images/cut.png</file>
    <file>images/new.png</file>
    <file>images/open.png</file>
    <file>images/paste.png</file>
    <file>images/save.png</file>
  </qresource>
</RCC>