QKeyEvent nativeVirtualKey未定义

Question

我需要QML应用程序中密钥的本机密钥代码。我在QML项中有以下键处理程序。

            Keys.onPressed: {
                console.log("Key: ", event.key)
                console.log("Native: ", event.nativeVirtualKey);
                event.accepted = true
            }

当按下键时，event.key工作得很好，但是event.nativeVirtualKey没有定义。例如：

qml: Key:  70
qml: Native:  undefined

我的密码有问题吗？我怎样才能得到nativeVirtualKey？

我在文档中看到了“注意:本机虚拟键可能是0，即使键事件包含扩展信息”，https://doc.qt.io/qt-5/qkeyevent.html#nativeVirtualKey不幸地没有提到什么时候或什么条件导致虚拟本机密钥消失。

Answer 1

正如我在this answer中已经指出的：KeyEvent不是一个QKeyEvent，而是一个公开一些属性但不是所有属性的QObject。解决方法是创建一个QObject，该将事件筛选器安装到该项并公开该属性：

#include <QGuiApplication>
#include <QQmlApplicationEngine>
#include <QQuickItem>

class KeyHelper: public QObject{
    Q_OBJECT
    Q_PROPERTY(QQuickItem* target READ target WRITE setTarget NOTIFY targetChanged)
public:
    using QObject::QObject;
    QQuickItem* target() const {
        return m_target;
    }
    void setTarget(QQuickItem* item){
        if(m_target)
            m_target->removeEventFilter(this);
        m_target = item;
        if(m_target)
            m_target->installEventFilter(this);
        Q_EMIT targetChanged(m_target);
    }
    bool eventFilter(QObject *watched, QEvent *event){
        if(watched == m_target && event->type() == QEvent::KeyPress){
            if(QKeyEvent *ke = static_cast<QKeyEvent *>(event))
                Q_EMIT nativeVirtualKeyChanged(ke->nativeVirtualKey());
        }
        return QObject::eventFilter(watched, event);
    }
signals:
    void nativeVirtualKeyChanged(quint32 nativeVirtualKey);
    void targetChanged(QQuickItem* item);
private:
    QPointer<QQuickItem> m_target;

};

int main(int argc, char *argv[])
{
    QCoreApplication::setAttribute(Qt::AA_EnableHighDpiScaling);
    QGuiApplication app(argc, argv);

    qmlRegisterType<KeyHelper>("qt.keyhelper", 1, 0, "KeyHelper");

    QQmlApplicationEngine engine;
    const QUrl url(QStringLiteral("qrc:/main.qml"));
    QObject::connect(&engine, &QQmlApplicationEngine::objectCreated,
                     &app, [url](QObject *obj, const QUrl &objUrl) {
        if (!obj && url == objUrl)
            QCoreApplication::exit(-1);
    }, Qt::QueuedConnection);
    engine.load(url);

    return app.exec();
}

#include "main.moc"

import QtQuick 2.12
import QtQuick.Window 2.12
import qt.keyhelper 1.0

Window {
    width: 640
    height: 480
    visible: true
    title: qsTr("Hello World")
    Item {
        id: item
        focus: true
        anchors.fill: parent
    }
   KeyHelper{
       target: item
       onNativeVirtualKeyChanged: console.log(nativeVirtualKey)
    }
}

Answer 2

这里对@eyllanesc的回答做了轻微的调整，它取代了eventFilter，将QEvent重新打包为QVariantMap，这样就可以用期望KeyEvent API的函数直接调用它。

class KeyHelper: public QObject{
     ... // same as @ellyanesc's answer

     bool eventFilter(QObject *watched, QEvent *event){
         if(watched == m_target && event->type() == QEvent::KeyPress){
             if(QKeyEvent *ke = static_cast<QKeyEvent *>(event)) {
                 // it seems we cannot send the event in a signal since it doesnt inherit from QObject.
                 // copy the relevant values to an event object
                 QVariantMap eventObject;
                 eventObject["key"] = ke->key();
                 eventObject["modifiers"] = int(ke->modifiers());
                 eventObject["nativeVirtualKey"] = ke->nativeVirtualKey();
                 eventObject["nativeModifiers"] = ke->nativeModifiers();
                 Q_EMIT nativeKeyPress(eventObject);
             }
         }
         return QObject::eventFilter(watched, event);
     }

signals:
     void nativeKeyPress(QVariantMap event); 

     ... // same as @ellyanesc's answer
};

然后在qml文件中

        KeyHelper{
            target: ...
            onNativeKeyPress: {
                console.log("native key press ", JSON.stringify(event))
            }
         }