I'm trying to pass QList
of integer from QML to C++ code, but somehow my approach is not working. With below approach am getting following error:
left of '->setParentItem' must point to class/struct/union/generic type
type is 'int *'
Any inputs to trouble shoot the issue is highly appreciated
Below is my code snippet
Header file
Q_PROPERTY(QDeclarativeListProperty<int> enableKey READ enableKey)
QDeclarativeListProperty<int> enableKey(); //function declaration
QList<int> m_enableKeys;
cpp file
QDeclarativeListProperty<int> KeyboardContainer::enableKey()
{
return QDeclarativeListProperty<int>(this, 0, &KeyboardContainer::append_list);
}
void KeyboardContainer::append_list(QDeclarativeListProperty<int> *list, int *key)
{
int *ptrKey = qobject_cast<int *>(list->object);
if (ptrKey) {
key->setParentItem(ptrKey);
ptrKey->m_enableKeys.append(key);
}
}
Connecting to QML Signals All QML signals are automatically available to C++, and can be connected to using QObject::connect() like any ordinary Qt C++ signal. In return, any C++ signal can be received by a QML object using signal handlers.
With the QML type compiler, you will be able to compile your object structure to C++. Each QML component becomes a C++ class this way.
Creating and Running QML Projects For simple UI files such as this one, select File > New File or Project > Application (Qt Quick) > Qt Quick Application - Empty from within Qt Creator. Pressing the green Run button runs the application. You should see the text Hello, World! in the center of a red rectangle.
Exposing Properties. A property can be specified for any QObject-derived class using the Q_PROPERTY() macro. A property is a class data member with an associated read function and optional write function. All properties of a QObject-derived or Q_GADGET class are accessible from QML.
You CAN'T use QDeclarativeListProperty (or QQmlListProperty in Qt5) with any other type than QObject derived ones. So int or QString will NEVER work.
If you need to exchange a QStringList or a QList or anything that is an array of one of the basic types supported by QML, the easiest way to do it is to use QVariant on the C++ side, like this :
#include <QObject>
#include <QList>
#include <QVariant>
class KeyboardContainer : public QObject {
Q_OBJECT
Q_PROPERTY(QVariant enableKey READ enableKey
WRITE setEnableKey
NOTIFY enableKeyChanged)
public:
// Your getter method must match the same return type :
QVariant enableKey() const {
return QVariant::fromValue(m_enableKey);
}
public slots:
// Your setter must put back the data from the QVariant to the QList<int>
void setEnableKey (QVariant arg) {
m_enableKey.clear();
foreach (QVariant item, arg.toList()) {
bool ok = false;
int key = item.toInt(&ok);
if (ok) {
m_enableKey.append(key);
}
}
emit enableKeyChanged ();
}
signals:
// you must have a signal named <property>Changed
void enableKeyChanged();
private:
// the private member can be QList<int> for convenience
QList<int> m_enableKey;
};
On the QML side, simply affect a JS array of Number, the QML engine will automatically convert it to QVariant to make it comprehensible to Qt :
KeyboardContainer.enableKeys = [12,48,26,49,10,3];
That's all !
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With