Set loader component by calling C++ function - c++

Question

I'm just wondering if anything like this is possible :
Loader {
id: loader
objectName: "loader"
anchors.centerIn: parent
sourceComponent: cppWrapper.getCurrentDisplay();
}
And in C++ :
QDeclarativeComponent currentDisplay;
and
Q_INVOKABLE QDeclarativeComponent getCurrentDisplay() const
{ return currentDisplay; }
I have trouble compiling it (it fails in the moc file compilation), but if it's possible, it can be a real shortcut for me

Answer 1

Sure, you can create Component in C++ part (as QQmlComponent) and return it to QML part.
Simple example (I use Qt 5.4):
First of all I create a class to use it as singleton (just for ease using)
common.h
#include <QObject>
#include <QQmlComponent>
class Common : public QObject
{
Q_OBJECT
public:
explicit Common(QObject *parent = 0);
~Common();
Q_INVOKABLE QQmlComponent *getComponent(QObject *parent);
};
common.cpp
QQmlComponent *Common::getComponent(QObject *parent) {
QQmlEngine *engine = qmlEngine(parent);
if(engine) {
QQmlComponent *component = new QQmlComponent(engine, QUrl("qrc:/Test.qml"));
return component;
}
return NULL;
}
Now I create and register my singleton:
main.cpp
#include "common.h"
static QObject *qobject_singletontype_provider(QQmlEngine *engine, QJSEngine *scriptEngine)
{
Q_UNUSED(engine)
Q_UNUSED(scriptEngine)
static Common *common = new Common();
return common;
}
int main(int argc, char *argv[])
{
QApplication app(argc, argv);
qmlRegisterSingletonType<Common>("Test", 1, 0, "Common", qobject_singletontype_provider);
QQmlApplicationEngine engine;
engine.load(QUrl(QStringLiteral("qrc:/main.qml")));
return app.exec();
}
Ok, now we have a singleton and it is very simple to use it in QML:
main.qml
import QtQuick 2.3
import Test 1.0
ApplicationWindow {
visible: true
width: 640
height: 480
title: qsTr("Hello World")
id: mainWindow
Loader {
id: loader
objectName: "loader"
anchors.centerIn: parent
sourceComponent: Common.getComponent(mainWindow)
}
}
Also our component we created in C++:
Test.qml
import QtQuick 2.3
Rectangle {
width: 100
height: 100
color: "green"
border.color: "yellow"
border.width: 3
radius: 10
}
Pay attention: all our QML files are in resource but it's just for example and you can put it in any place you want in your case