Qt 文字編輯器實作（上）：架構設計、動作建立與訊號槽連接

主視窗類別架構

class MainWindow : public QMainWindow {
    Q_OBJECT
public:
    MainWindow();
protected:
    void closeEvent(QCloseEvent *event);

private slots:
    void newFile();
    void open();
    bool save();
    bool saveAs();
    void about();
    void documentWasModified();

private:
    void createActions();
    void createMenus();
    void createToolBars();
    void createStatusBar();
    void readSettings();
    void writeSettings();
    bool maybeSave();
    void loadFile(const QString &fileName);
    bool saveFile(const QString &fileName);
    void setCurrentFile(const QString &fileName);
    QString strippedName(const QString &fullFileName);

    QTextEdit *textEdit;
    QString curFile;
    // 選單、工具列、動作指標...
};

Q_OBJECT 宏為訊號槽機制必要。

建構函式與關閉事件

MainWindow::MainWindow() {
    textEdit = new QTextEdit;
    setCentralWidget(textEdit);
    createActions();
    createMenus();
    createToolBars();
    createStatusBar();
    readSettings();
    connect(textEdit->document(), SIGNAL(contentsChanged()),
            this, SLOT(documentWasModified()));
    setCurrentFile("");
}

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

檔案操作 Slot

新增檔案

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

開啟檔案

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

儲存/另存新檔

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

bool MainWindow::saveAs() {
    QString fileName = QFileDialog::getSaveFileName(this);
    if (fileName.isEmpty()) return false;
    return saveFile(fileName);
}

關於對話框

void MainWindow::about() {
    QMessageBox::about(this, tr("About Application"),
        tr("The <b>Application</b> example created by <b>Yzs</b>"));
}

文件修改狀態追蹤

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

動作建立與連接

void MainWindow::createActions() {
    newAct = new QAction(QIcon(":/images/new.png"), 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(QIcon(":/images/open.png"), tr("&Open..."), this);
    openAct->setShortcut(tr("Ctrl+O"));
    connect(openAct, SIGNAL(triggered()), this, SLOT(open()));

    saveAct = new QAction(QIcon(":/images/save.png"), tr("&Save"), this);
    saveAct->setShortcut(tr("Ctrl+S"));
    connect(saveAct, SIGNAL(triggered()), this, SLOT(save()));

    saveAsAct = new QAction(tr("Save &As..."), this);
    connect(saveAsAct, SIGNAL(triggered()), this, SLOT(saveAs()));

    exitAct = new QAction(tr("E&xit"), this);
    exitAct->setShortcut(tr("Ctrl+Q"));
    connect(exitAct, SIGNAL(triggered()), this, SLOT(close()));

    cutAct = new QAction(QIcon(":/images/cut.png"), tr("Cu&t"), this);
    cutAct->setShortcut(tr("Ctrl+X"));
    connect(cutAct, SIGNAL(triggered()), textEdit, SLOT(cut()));

    copyAct = new QAction(QIcon(":/images/copy.png"), tr("&Copy"), this);
    copyAct->setShortcut(tr("Ctrl+C"));
    connect(copyAct, SIGNAL(triggered()), textEdit, SLOT(copy()));

    pasteAct = new QAction(QIcon(":/images/paste.png"), tr("&Paste"), this);
    pasteAct->setShortcut(tr("Ctrl+V"));
    connect(pasteAct, SIGNAL(triggered()), textEdit, SLOT(paste()));

    aboutAct = new QAction(tr("&About"), this);
    connect(aboutAct, SIGNAL(triggered()), this, SLOT(about()));

    aboutQtAct = new QAction(tr("About &Qt"), this);
    connect(aboutQtAct, SIGNAL(triggered()), qApp, SLOT(aboutQt()));

    // 剪貼/複製需有選取文字才啟用
    cutAct->setEnabled(false);
    copyAct->setEnabled(false);
    connect(textEdit, SIGNAL(copyAvailable(bool)), cutAct, SLOT(setEnabled(bool)));
    connect(textEdit, SIGNAL(copyAvailable(bool)), copyAct, SLOT(setEnabled(bool)));
}

QAction 封裝使用者操作，可同時加入選單與工具列。triggered() 訊號連接對應 slot 實作功能。編輯動作預設停用，透過 copyAvailable(bool) 訊號動態啟用。