QWebEngineView触摸滚动

分类：编程问答

如何解决QWebEngineView触摸滚动

我有一个从旧版Qt 4.7.4移植到Qt5的应用程序，据我了解，QWebView变成了QWebEngineView，并且在我使用FlickCharm的QWebView中，它在Qt示例中仍然可以与QScrollArea正常工作（例如QListWidget，QTableWidget，...，当然还有QScrollArea），但不再包含QWebEngineView，下面是激活FlickCharm的代码，该代码正在Qt4上运行：

void FlickCharm::activateOn(QWidget *widget,QWidget* p_viewport)
{
    QAbstractScrollArea *scrollArea = qobject_cast<QAbstractScrollArea*>(widget);
    if (scrollArea) {
        // Widget is a scroll area

        QAbstractItemView *itemView = qobject_cast<QAbstractItemView*>(widget);
        if(itemView)
        {
            itemView->setHorizontalScrollMode(QAbstractItemView::ScrollPerPixel);
            itemView->setVerticalScrollMode(QAbstractItemView::ScrollPerPixel);
        }

        QWidget *viewport = scrollArea->viewport();
        if ( p_viewport )
        {
            viewport = p_viewport;
        }
        else
        {
            scrollArea->installEventFilter(this);
        }

        viewport->installEventFilter(this);

        QHash<QWidget*,FlickData*>::iterator oldViewport;
        if ( ( oldViewport = d->flickData.find(viewport) ) != d->flickData.end() )
        {
            delete oldViewport.value();
        }

        d->flickData.remove(viewport);
        d->flickData[viewport] = new FlickData;
        d->flickData[viewport]->widget = widget;
        d->flickData[viewport]->state = FlickData::Steady;
        d->flickData[viewport]->customViewPort = (viewport != scrollArea->viewport());

        return;
    }

    QWebView *webView = qobject_cast<QWebView*>(widget);
    if (webView) {
        // Widget is a web view
        webView->installEventFilter(this);

        QHash<QWidget*,FlickData*>::iterator oldViewport;
        if ( ( oldViewport = d->flickData.find(webView) ) != d->flickData.end() )
        {
            delete oldViewport.value();
        }

        d->flickData.remove(webView);
        d->flickData[webView] = new FlickData;
        d->flickData[webView]->widget = webView;
        d->flickData[webView]->state = FlickData::Steady;

        return;
    }

    qWarning() << "FlickCharm only works on QAbstractScrollArea (and derived classes)";
    qWarning() << "or QWebView (and derived classes)";
}

在FlickData类中，有以下函数可以进行滚动：

bool scrollWidget(const int dx,const int dy)
    {
        {
            QAbstractScrollArea *scrollArea = qobject_cast<QAbstractScrollArea*>(widget);
            if (scrollArea) {
                const int x = scrollArea->horizontalScrollBar()->value();
                const int y = scrollArea->verticalScrollBar()->value();
                scrollArea->horizontalScrollBar()->setValue(x - dx);
                scrollArea->verticalScrollBar()->setValue(y - dy);
                return (scrollArea->horizontalScrollBar()->value() != x
                        || scrollArea->verticalScrollBar()->value() != y);
            }
        }

        {
            QWebEngineView *webEngineView = qobject_cast<QWebEngineView*>(widget);
            if (webEngineView) {
                const QPointF position = webEngineView->page()->scrollPosition();
                const QPointF newPosition = position - QPointF(dx,dy);
                webEngineView->page()->runJavaScript(QString("window.scrollTo(%1,%2);").arg(newPosition.x()).arg(newPosition.y()));
                return webEngineView->page()->scrollPosition() != position;
            }
        }
        return false;
    }

在Qt5中，我尝试如上所述直接应用于QWebEngineView：

    QWebEngineView *webEngineView = qobject_cast<QWebEngineView*>(widget);
    if (webEngineView) {
        webEngineView->installEventFilter(this);

        QHash<QWidget*,FlickData*>::iterator oldViewport;
        if ( ( oldViewport = d->flickData.find(webEngineView) ) != d->flickData.end() )
        {
            delete oldViewport.value();
        }

        d->flickData.remove(webEngineView);
        d->flickData[webEngineView] = new FlickData;
        d->flickData[webEngineView]->widget = webEngineView;
        d->flickData[webEngineView]->state = FlickData::Steady;

        return;
    }

并且还尝试分页显示我认为是视口的视图：

    QWebEngineView *webEngineView = qobject_cast<QWebEngineView*>(widget);
    if (webEngineView) {
        QWidget *viewport = webEngineView->page()->view();

        webEngineView->installEventFilter(this);
        viewport->installEventFilter(this);

        QHash<QWidget*,FlickData*>::iterator oldViewport;
        if ( ( oldViewport = d->flickData.find(viewport) ) != d->flickData.end() )
        {
            delete oldViewport.value();
        }

        d->flickData.remove(viewport);
        d->flickData[viewport] = new FlickData;
        d->flickData[viewport]->widget = webEngineView;
        d->flickData[viewport]->state = FlickData::Steady;

        return;
    }

在QWebEngineView :: page（）（即QWebEnginePage）中，有一个scrollPosition（）函数，但这来自Q_PROPERTY，但没有写访问器函数，但是我发现一个可以和平使用我尝试使用的javascript滚动的代码：

    QWebEngineView *webEngineView = qobject_cast<QWebEngineView*>(widget);
    if (webEngineView) {
        const QPointF position = webEngineView->page()->scrollPosition();
        const QPointF newPosition = position - QPointF(dx,dy);
        webEngineView->page()->runJavaScript(QString("window.scrollTo(%1,%2);").arg(newPosition.x()).arg(newPosition.y()));
        return webEngineView->page()->scrollPosition() != position;
    }

但是在添加一些日志后，我看到我从未传递过QWebEngineView的scrollWidget，并且由于我拥有自己的实例化了继承了QApplication的类，因此我可以看到，它不是直接单击的QWebEngineView，而是一个RenderWidgetHostViewQtDelegateWidget（的QWebEngineView作为父级）（无法从任何地方访问），我看到了这一点，因为我重新实现了MyApplication :: notify来登录单击了哪些小部件：

bool MyApplication::notify(QObject* p_object,QEvent* p_event)
{
    [...]
    if ( p_event->type() == QEvent::MouseButtonPress )
    {
        QWidget* widget = dynamic_cast<QWidget*>(p_object);
        if (widget != 0)
        {
            qDebug().nospace() << "Mouse pressed on [" << (widget->isEnabled() ? "enabled" :"disabled") << "] widget: "
                               << p_object
                               << ",parent: " << p_object->parent();
        }
        else
        {
            qDebug().nospace() << "Mouse pressed on object: " << p_object
                               << ",parent: " << p_object->parent();
        }
    }
    else if ( p_event->type() == QEvent::MouseButtonRelease )
    {
        QWidget* widget = dynamic_cast<QWidget*>(p_object);
        if (widget != 0)
        {
            qDebug().nospace() << "Mouse release on [" << (widget->isEnabled() ? "enabled" :"disabled") << "] widget: "
                               << p_object
                               << ",parent: " << p_object->parent();
        }
        else
        {
            qDebug().nospace() << "Mouse release on object: " << p_object
                               << ",parent: " << p_object->parent();
        }
    }
    [...]
}

此外，当我尝试在QWebEngineView上滚动时，将改为选择文本。

这是flickcharm的完整代码：https://doc.qt.io/archives/qt-4.8/qt-demos-embedded-anomaly-src-flickcharm-cpp.html

此外，我已经看到有一种使WebEngineView可滑动的解决方案，但仅适用于QtQuick QML：https://stackoverflow.com/a/42817245

任何人都知道如何在QWebEngineView上进行触摸滚动吗？

谢谢

编辑：由于RenderWidgetHostViewQtDelegateWidget是QWebEngineView的子级，因此我尝试从webEngineView-> children（）访问它（如果可能的话，至少作为QWidget），但未成功，因为其唯一的子级是其QVBoxLayout（为空） ）和FlickCharm。

解决方法

我终于在FlickCharm :: activateOn为我放置的QWebEngineView中做我想做的事情：

        QWebEngineView *webEngineView = qobject_cast<QWebEngineView*>(widget);
        if (webEngineView) {
            QLayout* webEngineViewLayout = webEngineView->layout();
            QWidget* webEngineViewChildWidget = 0;
            for (int i = 0; i < webEngineViewLayout->count(); ++i)
            {
                webEngineViewChildWidget = qobject_cast<QWidget*>(webEngineViewLayout->itemAt(i)->widget());

                if (webEngineViewChildWidget != nullptr)
                {
                    // There should be only one QWidget under QWebEngineView,but break just in case
                    break;
                }
            }

            if (webEngineViewChildWidget != nullptr)
            {
               // Install event filter on widget found in QWebEngineView layout
                webEngineViewChildWidget->installEventFilter(this);

                QHash<QWidget*,FlickData*>::iterator oldViewport;
                if ( ( oldViewport = d->flickData.find(webEngineViewChildWidget) ) != d->flickData.end() )
                {
                    delete oldViewport.value();
                }

                d->flickData.remove(webEngineViewChildWidget);
                d->flickData[webEngineViewChildWidget] = new FlickData;
                d->flickData[webEngineViewChildWidget]->widget = webEngineView;
                d->flickData[webEngineViewChildWidget]->state = FlickData::Steady;
            }
            else
            {
                // Web engine view has not yet a page loaded,activate "again" when a page has been loaded
                connect(webEngineView,&QWebEngineView::loadFinished,this,&FlickCharm::ReactToWebEngineViewLoaded);
            }

            return;
        }

FlickCharm::ReactToWebEngineViewLoaded()是：

void FlickCharm::ReactToWebEngineViewLoaded()
{
    QWebEngineView* webEngineView = qobject_cast<QWebEngineView*>(sender());

    if (webEngineView != nullptr)
    {
        // We need to pass only once there then we can disconnect now
        disconnect(webEngineView,&FlickCharm::ReactToWebEngineViewLoaded);

        // Activate "again" so that view actually uses flick charm
        activateOn(webEngineView);
    }
    else
    {
        LOG_ERROR("Web engine view is NULL");
        assert(webEngineView != nullptr);
    }
}

当然void ReactToWebEngineViewLoaded()被声明为flickcharm.h中的广告位。

在FlickData::scrollWidget中使用QWebEngineView （这很棘手，我不喜欢qApp-> processEvents调用，但是如果我们要实际比较值以返回函数，则必须使用它们）：


            QWebEngineView *webEngineView = qobject_cast<QWebEngineView*>(widget);
            if (webEngineView) {
                 webEngineView->page()->runJavaScript(QString("window.scrollBy(%1,%2);").arg(-dx).arg(-dy));
                return true;
            }

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