Qt 5.12
Qt QML
C++ Extensions: Network Access Manager Factory Example
main.cpp Example File
Qt 5.12.12 Reference Documentation
main.cpp Example File

networkaccessmanagerfactory/main.cpp
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 #include <QCommandLineParser>
 #include <QGuiApplication>
 #include <QNetworkAccessManager>
 #include <QNetworkProxy>

 #include <QQmlEngine>
 #include <QQmlNetworkAccessManagerFactory>
 #include <QtQuick/QQuickView>

 /*
    This example illustrates using a QQmlNetworkAccessManagerFactory to
    create a QNetworkAccessManager with a proxy.

    Usage:
      networkaccessmanagerfactory [-host <proxy> -port <port>] [file]
 */

 #if QT_CONFIG(networkproxy)
 static QString proxyHost;
 static int proxyPort = 0;
 #endif // networkproxy

 class MyNetworkAccessManagerFactory : public QQmlNetworkAccessManagerFactory
 {
 public:
     QNetworkAccessManager *create(QObject *parent) override;
 };

 QNetworkAccessManager *MyNetworkAccessManagerFactory::create(QObject *parent)
 {
     QNetworkAccessManager *nam = new QNetworkAccessManager(parent);
 #if QT_CONFIG(networkproxy)
     if (!proxyHost.isEmpty()) {
         qDebug() << "Created QNetworkAccessManager using proxy" << (proxyHost + ":" + QString::number(proxyPort));
         QNetworkProxy proxy(QNetworkProxy::HttpCachingProxy, proxyHost, proxyPort);
         nam->setProxy(proxy);
     }
 #endif // networkproxy

     return nam;
 }

 int main(int argc, char ** argv)
 {
     QUrl source("qrc:view.qml");

     QGuiApplication app(argc, argv);

     QCommandLineParser parser;
 #if QT_CONFIG(networkproxy)
     QCommandLineOption proxyHostOption("host", "The proxy host to use.", "host");
     parser.addOption(proxyHostOption);
     QCommandLineOption proxyPortOption("port", "The proxy port to use.", "port", "0");
     parser.addOption(proxyPortOption);
 #endif // networkproxy
     parser.addPositionalArgument("file", "The file to use.");
     QCommandLineOption helpOption = parser.addHelpOption();
     parser.setSingleDashWordOptionMode(QCommandLineParser::ParseAsLongOptions);
     QStringList arguments = QCoreApplication::arguments();
     if (!parser.parse(arguments)) {
         qWarning() << parser.helpText() << '\n' << parser.errorText();
         exit(1);
     }
     if (parser.isSet(helpOption)) {
         qWarning() << parser.helpText();
         exit(0);
     }
 #if QT_CONFIG(networkproxy)
     if (parser.isSet(proxyHostOption))
         proxyHost = parser.value(proxyHostOption);
     if (parser.isSet(proxyPortOption)) {
         bool ok = true;
         proxyPort = parser.value(proxyPortOption).toInt(&ok);
         if (!ok || proxyPort < 1 || proxyPort > 65535) {
             qWarning() << parser.helpText() << "\nNo valid port given. It should\
                           be a number between 1 and 65535";
             exit(1);
         }
     }
 #endif // networkproxy
     if (parser.positionalArguments().count() == 1)
         source = QUrl::fromLocalFile(parser.positionalArguments().first());

     QQuickView view;
     MyNetworkAccessManagerFactory networkManagerFactory;
     view.engine()->setNetworkAccessManagerFactory(&networkManagerFactory);

     view.setSource(source);
     view.show();

     return app.exec();
 }