DOM 书签应用程序

提供了一个用于读取 XML 书签交换语言 (XBEL) 文件的解析器。

DOM 书签应用程序提供了一个用于读取 XML 书签交换语言 (XBEL) 文件的解析器，该解析器利用 Qt 基于 DOM 的 XML API 来读取和解析文件。QXmlStream 书签示例提供了读取此类文件的另一种方法。

带有“标题”和“位置”列的书签树

XbelTree 类的定义

XbelTree类提供了用于读写文件系统的函数。它继承自QTreeWidget 类，包含用于显示书签的模型，并支持对书签进行编辑。

class XbelTree : public QTreeWidget
{
    Q_OBJECT

public:
    explicit XbelTree(QWidget *parent = nullptr);

    bool read(QIODevice *device);
    bool write(QIODevice *device) const;

protected:
#if QT_CONFIG(clipboard) && QT_CONFIG(contextmenu)
    void contextMenuEvent(QContextMenuEvent *event) override;
#endif

private slots:
    void updateDomElement(const QTreeWidgetItem *item, int column);

private:
    void parseFolderElement(const QDomElement &element,
                            QTreeWidgetItem *parentItem = nullptr);
    QTreeWidgetItem *createItem(const QDomElement &element,
                                QTreeWidgetItem *parentItem = nullptr);

    QDomDocument domDocument;
    QIcon folderIcon;
    QIcon bookmarkIcon;
};

XbelTree类的实现

XbelTree 构造函数接受一个QWidget ，该类将被放置其中。folderIcon 被设置为QIcon::Normal模式，即仅当用户未与图标交互时才显示位图。QStyle::SP_DirClosedIcon 、QStyle::SP_DirOpenIcon 和QStyle::SP_FileIcon 分别对应遵循您GUI风格的标准位图。

XbelTree::XbelTree(QWidget *parent)
    : QTreeWidget(parent)
{
    header()->setSectionResizeMode(QHeaderView::Stretch);
    setHeaderLabels({tr("Title"), tr("Location")});

    folderIcon.addPixmap(style()->standardPixmap(QStyle::SP_DirClosedIcon),
                         QIcon::Normal, QIcon::Off);
    folderIcon.addPixmap(style()->standardPixmap(QStyle::SP_DirOpenIcon),
                         QIcon::Normal, QIcon::On);
    bookmarkIcon.addPixmap(style()->standardPixmap(QStyle::SP_FileIcon));
}

read() 函数使用QDomDocument::setContent 打开指定的QIODevice 文件。如果成功打开文件且顶层头文件已通过验证，则会在解析文件内容之前清空类的当前内容，随后通过遍历所有顶层XML节点，并对每个节点调用parseFolderElement() 来解析文件内容。

bool XbelTree::read(QIODevice *device)
{
    QDomDocument::ParseResult result =
            domDocument.setContent(device, QDomDocument::ParseOption::UseNamespaceProcessing);
    if (!result) {
        QMessageBox::information(window(), tr("DOM Bookmarks"),
                                 tr("Parse error at line %1, column %2:\n%3")
                                         .arg(result.errorLine)
                                         .arg(result.errorColumn)
                                         .arg(result.errorMessage));
        return false;
    }

    QDomElement root = domDocument.documentElement();
    if (root.tagName() != "xbel") {
        QMessageBox::information(window(), tr("DOM Bookmarks"),
                                 tr("The file is not an XBEL file."));
        return false;
    } else if (root.hasAttribute(versionAttribute)
               && root.attribute(versionAttribute) != "1.0"_L1) {
        QMessageBox::information(window(), tr("DOM Bookmarks"),
                                 tr("The file is not an XBEL version 1.0 "
                                    "file."));
        return false;
    }

    clear();

    disconnect(this, &QTreeWidget::itemChanged, this, &XbelTree::updateDomElement);

    QDomElement child = root.firstChildElement(folderElement);
    while (!child.isNull()) {
        parseFolderElement(child);
        child = child.nextSiblingElement(folderElement);
    }

    connect(this, &QTreeWidget::itemChanged, this, &XbelTree::updateDomElement);

    return true;
}

parseFolderElement() 函数负责处理不同的元素类型，若元素为子文件夹，则递归调用自身。

void XbelTree::parseFolderElement(const QDomElement &element,
                                  QTreeWidgetItem *parentItem)
{
    QTreeWidgetItem *item = createItem(element, parentItem);

    QString title = element.firstChildElement(titleElement).text();
    if (title.isEmpty())
        title = tr("Folder");

    item->setFlags(item->flags() | Qt::ItemIsEditable);
    item->setIcon(0, folderIcon);
    item->setText(0, title);

    bool folded = (element.attribute(foldedAttribute) != "no"_L1);
    item->setExpanded(!folded);

    constexpr char16_t midDot = u'\xB7';
    static const QString dots = QString(30, midDot);
    QDomElement child = element.firstChildElement();
    while (!child.isNull()) {
        if (child.tagName() == folderElement) {
            parseFolderElement(child, item);
        } else if (child.tagName() == bookmarkElement) {
            QTreeWidgetItem *childItem = createItem(child, item);

            QString title = child.firstChildElement(titleElement).text();
            if (title.isEmpty())
                title = tr("Folder");

            childItem->setFlags(item->flags() | Qt::ItemIsEditable);
            childItem->setIcon(0, bookmarkIcon);
            childItem->setText(0, title);
            childItem->setText(1, child.attribute(hrefAttribute));
        } else if (child.tagName() == "separator"_L1) {
            QTreeWidgetItem *childItem = createItem(child, item);
            childItem->setFlags(item->flags() & ~(Qt::ItemIsSelectable | Qt::ItemIsEditable));
            childItem->setText(0, dots);
        }
        child = child.nextSiblingElement();
    }
}

write() 函数通过QDomDocument::save将domDocument保存到指定的QIODevice 中。

bool XbelTree::write(QIODevice *device) const
{
    const int IndentSize = 4;

    QTextStream out(device);
    domDocument.save(out, IndentSize);
    return true;
}

MainWindow 类的定义

MainWindow 类是QMainWindow 的子类，具有File 菜单和Help 菜单。

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    MainWindow();

public slots:
    void open();
    void saveAs();
    void about();

private:
    void createMenus();

    XbelTree *xbelTree;
};

MainWindow类的实现

MainWindow 的构造函数会实例化成员对象 XbelTree，并将其标题设置为QStringList 对象labels 。该构造函数还会调用createMenus() 来设置菜单。statusBar() 用于显示“Ready”消息。

MainWindow::MainWindow()
{
    xbelTree = new XbelTree;
    setCentralWidget(xbelTree);

    createMenus();

    statusBar()->showMessage(tr("Ready"));

    setWindowTitle(tr("DOM Bookmarks"));
    const QSize availableSize = screen()->availableGeometry().size();
    resize(availableSize.width() / 2, availableSize.height() / 3);
}

createMenus() 函数用于填充菜单并设置键盘快捷键。

void MainWindow::createMenus()
{
    QMenu *fileMenu = menuBar()->addMenu(tr("&File"));
    QAction *openAct = fileMenu->addAction(tr("&Open..."), this, &MainWindow::open);
    openAct->setShortcuts(QKeySequence::Open);

    QAction *saveAsAct = fileMenu->addAction(tr("&Save As..."), this, &MainWindow::saveAs);
    saveAsAct->setShortcuts(QKeySequence::SaveAs);

    QAction *exitAct = fileMenu->addAction(tr("E&xit"), this, &QWidget::close);
    exitAct->setShortcuts(QKeySequence::Quit);

    menuBar()->addSeparator();

    QMenu *helpMenu = menuBar()->addMenu(tr("&Help"));
    helpMenu->addAction(tr("&About"), this, &MainWindow::about);
    helpMenu->addAction(tr("About &Qt"), qApp, &QApplication::aboutQt);
}

open() 函数允许用户通过QFileDialog 打开XBEL文件。如果文件无法读取或出现解析错误，则会显示一条警告消息，并同时调用fileName 和errorString 。如果操作成功，则调用XbelTree::read() 。

void MainWindow::open()
{
    QFileDialog fileDialog(this, tr("Open Bookmark File"), QDir::currentPath());
    fileDialog.setMimeTypeFilters({"application/x-xbel"_L1});
    if (fileDialog.exec() != QDialog::Accepted)
        return;

    const QString fileName = fileDialog.selectedFiles().constFirst();
    QFile file(fileName);
    if (!file.open(QFile::ReadOnly | QFile::Text)) {
        QMessageBox::warning(this, tr("DOM Bookmarks"),
                             tr("Cannot read file %1:\n%2.")
                             .arg(QDir::toNativeSeparators(fileName),
                                  file.errorString()));
        return;
    }

    if (xbelTree->read(&file))
        statusBar()->showMessage(tr("File loaded"), 2000);
}

saveAs() 函数会显示QFileDialog ，并提示用户输入fileName 。与open() 函数类似，如果无法向文件写入数据，该函数也会显示警告消息。若操作成功，则调用XbelTree::write() 。

void MainWindow::saveAs()
{
    QFileDialog fileDialog(this, tr("Save Bookmark File"), QDir::currentPath());
    fileDialog.setAcceptMode(QFileDialog::AcceptSave);
    fileDialog.setDefaultSuffix("xbel"_L1);
    fileDialog.setMimeTypeFilters({"application/x-xbel"_L1});
    if (fileDialog.exec() != QDialog::Accepted)
        return;

    const QString fileName = fileDialog.selectedFiles().constFirst();
    QFile file(fileName);
    if (!file.open(QFile::WriteOnly | QFile::Text)) {
        QMessageBox::warning(this, tr("DOM Bookmarks"),
                             tr("Cannot write file %1:\n%2.")
                             .arg(QDir::toNativeSeparators(fileName),
                                  file.errorString()));
        return;
    }

    if (xbelTree->write(&file))
        statusBar()->showMessage(tr("File saved"), 2000);
}

about() 函数会显示QMessageBox ，并附上该示例的简要说明。

void MainWindow::about()
{
   QMessageBox::about(this, tr("About DOM Bookmarks"),
                      tr("The <b>DOM Bookmarks</b> example demonstrates how to "
                         "use Qt's DOM classes to read and write XML "
                         "documents."));
}

有关 XBEL 文件的更多信息，请参阅XML 书签交换语言资源页面。

示例项目 @ code.qt.io

从 Qt 5 升级

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