I need the native key code of a key in my QML application. I have the following key handler in a QML item.
Keys.onPressed: {
console.log("Key: ", event.key)
console.log("Native: ", event.nativeVirtualKey);
event.accepted = true
}
The event.key
works fine when pressing keys, but the event.nativeVirtualKey
was undefined. eg.
qml: Key: 70
qml: Native: undefined
Is something wrong with my code? How can I get the nativeVirtualKey?
I'm seeing in the documentation now that "Note: The native virtual key may be 0, even if the key event contains extended information." https://doc.qt.io/qt-5/qkeyevent.html#nativeVirtualKey Unfortunately there is no mention of when or which conditions cause the virtual native key to disappear.
As I already pointed out in this answer : KeyEvent
is not a QKeyEvent
but a QObject that exposes some properties but not all. A workaround is to create a QObject that installs an event filter to the item and exposes that property:
#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)
}
}
Here is a slight adjustment of @eyllanesc's answer that replaces eventFilter
to repackage the QEvent as a QVariantMap so that it can be directly called with functions that expect the KeyEvent
API.
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
};
And then in the qml file
KeyHelper{
target: ...
onNativeKeyPress: {
console.log("native key press ", JSON.stringify(event))
}
}
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