如何在QML应用程序中安装和使用Qt C编写的事件过滤器

#include <QtGui>
#include <QtQml>

class ShortcutListener : public QObject
{
    Q_OBJECT

public:
    ShortcutListener(QObject *parent = nullptr) :
        QObject(parent)
    {
    }

    Q_INVOKABLE void listenTo(QObject *object)
    {
        if (!object)
            return;

        object->installEventFilter(this);
    }

    bool eventFilter(QObject *object,QEvent *event) override
    {
        if (event->type() == QEvent::KeyPress) {
            QKeyEvent *keyEvent = static_cast<QKeyEvent*>(event);
            qDebug() << "key" << keyEvent->key() << "pressed on" << object;
            return true;
        }
        return false;
    }
};

static QObject *shortcutListenerInstance(QQmlEngine *,QJSEngine *engine)
{
    return new ShortcutListener(engine);
}

int main(int argc,char *argv[])
{
    QGuiApplication app(argc,argv);

    qmlRegisterSingletonType<ShortcutListener>("App",1,"ShortcutListener",shortcutListenerInstance);

    QQmlApplicationEngine engine;
    engine.load(QUrl(QStringLiteral("qrc:/main.qml")));

    return app.exec();
}

#include "main.moc"

main.qml：

import QtQuick 2.5
import QtQuick.Window 2.2

import App 1.0

Window {
    id: window
    width: 640
    height: 480
    visible: true

    Component.onCompleted: ShortcutListener.listenTo(window)
}

如果你有几个不同的监听器,你也可以通过向ShortcutListener添加一个对象属性来声明性地执行它,它将在设置时安装事件过滤器.

有关详细信息,请参阅Integrating QML and C++.