WebEngine 通知范例

演示如何将 HTML5 Web 通知传递给用户。

WebEngine 通知 演示如何使用 QWebEngineProfile::setNotificationPresenter () 方法和 QWebEngineNotification 类去向用户展示 HTML5 Web 通知。

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HTML 页面

In this example, we create an internal HTML page that is added through a resource collection file (.qrc). The page displays buttons for requesting permissions and contains necessary JavaScript code to trigger this request:

            Notification.requestPermission().then(function (permission) {
                if (permission == 'granted')
                    createNotification()
            })

Also page contains a button for creating a notification. The following JavaScript constructions are executed on the press event:

    function createNotification() {
        let title = 'Notification #' + ++notificationsCreated
        let options = { body: 'Visit doc.qt.io for more info!', icon: 'icon.png', }
        let notification = new Notification(title, options)
    }

main 函数

在 main 函数，实例化 QWebEngineView , load our internal HTML page, and set up the required callbacks for notifications handling.

请求特征权限

We then use the QWebEnginePage::featurePermissionRequested () call to request the user's permission to show notifications on their device.

    QObject::connect(view.page(), &QWebEnginePage::featurePermissionRequested,
                     [&] (const QUrl &origin, QWebEnginePage::Feature feature) {
                         if (feature != QWebEnginePage::Notifications)
                             return;
                         view.page()->setFeaturePermission(origin, feature, QWebEnginePage::PermissionGrantedByUser);
                     });

处理新通知

We then construct a NotificationPopup that encapsulates the data of the HTML web notification. We also use the QWebEngineProfile::setNotificationPresenter () call to set our handler, which we use in conjunction with our popup to handle all new notifications.

    auto popup = new NotificationPopup(&view);
    profile->setNotificationPresenter([&] (std::unique_ptr<QWebEngineNotification> notification)
                                      { popup->present(notification); });

向用户呈现通知

The NotificationPopup class in this example is a simple QWidget -based class that uses multiple QLabel instances for displaying the notification's title, message, and icon.

class NotificationPopup : public QWidget
{
    Q_OBJECT
    QLabel m_icon, m_title, m_message;
    std::unique_ptr<QWebEngineNotification> notification;

呈现通知

Inside the present method, we first close and release the previous notification if we have one and then take ownership of a new notification by calling the std::unique_ptr::swap method on our internal notification instance.

    void present(std::unique_ptr<QWebEngineNotification> &newNotification)
    {
        if (notification) {
            notification->close();
            notification.reset();
        }
        notification.swap(newNotification);

Then we query the notification instance for a title, a message, and an icon by calling QWebEngineNotification::title (), QWebEngineNotification::message (), QWebEngineNotification::icon () and set up the appropriate labels in our popup.

        m_title.setText("<b>" + notification->title() + "</b>");
        m_message.setText(notification->message());
        m_icon.setPixmap(QPixmap::fromImage(notification->icon()).scaledToHeight(m_icon.height()));

After that we are ready to display our notification to the user by calling the QWidget::show () method. On this step we also call the QWebEngineNotification::show () method to notify JavaScript code about our show 事件。

        show();
        notification->show();

Finally, we set up a callback to handle the close event from the JavaScript side by connecting to the QWebEngineNotification::closed () signal. We also schedule a timer event to close our active notification automatically.

        connect(notification.get(), &QWebEngineNotification::closed, this, &NotificationPopup::onClosed);
        QTimer::singleShot(10000, notification.get(), [&] () { onClosed(); });
    }

关闭活动通知

We execute the close step for the currently active notification either by timeout or by handling the JavaScript event. First, we hide the popup widget itself by calling QWidget::hide (). Then, we notify the JavaScript code by calling the QWebEngineNotification::close () method. Finally, we destroy the notification object through the std::unique_ptr::reset() 方法。

    void onClosed()
    {
        hide();
        notification->close();
        notification.reset();
    }

实现用户交互

To implement the click step for a notification, we handle mouse interaction through QWidget::mouseReleaseEvent (). On this event, the JavaScript code is notified by calling the QWebEngineNotification::click () method. Then we automatically perform the close step as a notification is considered fully handled and no longer needed, and therefore can be destroyed.

    void mouseReleaseEvent(QMouseEvent *event) override
    {
        QWidget::mouseReleaseEvent(event);
        if (notification && event->button() == Qt::LeftButton) {
            notification->click();
            onClosed();
        }
    }

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