WebEngine Widgets Html2Pdf 范例

以 Qt WebEngine 将网页转换成 PDF 文档。

Html2Pdf demonstrates how to use Qt WebEngine to implement a command-line application for converting web pages into PDF documents.

运行范例

要运行范例从 Qt Creator ，打开 Welcome 模式，然后选择范例从 Examples 。更多信息，拜访 构建和运行范例 .

The Conversion Process

In order to convert a web page into a PDF document we need to:

1. 创建 QWebEngineView .
2. 告诉 QWebEngineView to begin loading the target URL and wait for it to finish.
3. 告诉 QWebEngineView to begin converting the loaded page into a PDF file and again wait for it to finish.
4. Once the conversion is finished, exit the program.

This process is encapsulated in the Html2PdfConverter 类：

#include <QApplication>
#include <QCommandLineParser>
#include <QFile>
#include <QTextStream>
#include <QWebEngineView>
#include <functional>
using namespace std;
using namespace std::placeholders;
class Html2PdfConverter : public QObject
{
    Q_OBJECT
public:
    explicit Html2PdfConverter(QString inputPath, QString outputPath);
    int run();
private slots:
    void loadFinished(bool ok);
    void pdfPrintingFinished(const QString &filePath, bool success);
private:
    QString m_inputPath;
    QString m_outputPath;
    QScopedPointer<QWebEngineView> m_view;
};
					

In the constructor we create the QWebEngineView and connect to its QWebEngineView::loadFinished and QWebEngineView::pdfPrintingFinished signals:

Html2PdfConverter::Html2PdfConverter(QString inputPath, QString outputPath)
    : m_inputPath(move(inputPath))
    , m_outputPath(move(outputPath))
    , m_view(new QWebEngineView)
{
    connect(m_view.data(), &QWebEngineView::loadFinished,
            this, &Html2PdfConverter::loadFinished);
    connect(m_view.data(), &QWebEngineView::pdfPrintingFinished,
            this, &Html2PdfConverter::pdfPrintingFinished);
}
					

The run() method will trigger the conversion process by asking QWebEnginePage to start loading the target URL. We then enter the main event loop:

int Html2PdfConverter::run()
{
    m_view->load(QUrl::fromUserInput(m_inputPath));
    return QApplication::exec();
}
					

After the loading is finished we begin PDF generation. We ask the QWebEnginePage::printToPdf method to write the output directly to disk:

void Html2PdfConverter::loadFinished(bool ok)
{
    if (!ok) {
        QTextStream(stderr)
            << tr("failed to load URL '%1'").arg(m_inputPath) << "\n";
        QCoreApplication::exit(1);
        return;
    }
    m_view->printToPdf(m_outputPath);
}
					

Once we receive the signal that the PDF conversion has finished, all that remains is to report potential errors and exit the program:

void Html2PdfConverter::pdfPrintingFinished(const QString &filePath, bool success)
{
    if (!success) {
        QTextStream(stderr)
            << tr("failed to print to output file '%1'").arg(filePath) << "\n";
        QCoreApplication::exit(1);
    } else {
        QCoreApplication::quit();
    }
}
					

main 函数

Our main function is responsible for setting up a QApplication and parsing command line arguments:

int main(int argc, char *argv[])
{
    QApplication app(argc, argv);
    QCoreApplication::setOrganizationName("QtExamples");
    QCoreApplication::setApplicationName("html2pdf");
    QCoreApplication::setApplicationVersion(QT_VERSION_STR);
    QCommandLineParser parser;
    parser.setApplicationDescription(
        QCoreApplication::translate("main", "Converts the web page INPUT into the PDF file OUTPUT."));
    parser.addHelpOption();
    parser.addVersionOption();
    parser.addPositionalArgument(
        QCoreApplication::translate("main", "INPUT"),
        QCoreApplication::translate("main", "Input URL for PDF conversion."));
    parser.addPositionalArgument(
        QCoreApplication::translate("main", "OUTPUT"),
        QCoreApplication::translate("main", "Output file name for PDF conversion."));
    parser.process(QCoreApplication::arguments());
    const QStringList requiredArguments = parser.positionalArguments();
    if (requiredArguments.size() != 2)
        parser.showHelp(1);
    Html2PdfConverter converter(requiredArguments.at(0), requiredArguments.at(1));
    return converter.run();
}
					

Note that to use Qt WebEngine Widgets we need to create a QApplication and not a QCoreApplication , even though this is a command line application.

范例工程 @ code.qt.io

内容

• 运行范例

• The Conversion Process

• main 函数