I'm trying to create a hybrid QML/C++ application, where the logic is
written in C++ and the interface is QML/Sailfish Silica based.
I'm currently playing around with the different ways to let QML/C++
communicate with each other. I currently have this code:
<code>
#include <QApplication>
#include <QGraphicsObject>
#include <QDir>
#include <QDeclarativeView>
#include <QDeclarativeContext>
#include <QDeclarativeEngine>
#include <QDeclarativeComponent>
#include <QDebug>
#include <QDeclarativePropertyMap>
#ifdef HAS_BOOSTER
#include <MDeclarativeCache>
#endif
Q_DECL_EXPORT int main(int argc, char *argv[])
{
#ifdef HAS_BOOSTER
QScopedPointer<QApplication>
myapp(MDeclarativeCache::qApplication(argc, argv));
#else
QScopedPointer<QApplication> myapp = new QApplication(argc, argv);
#endif
#ifdef HAS_BOOSTER
QScopedPointer<QDeclarativeView>
appview(MDeclarativeCache::qDeclarativeView());
#else
QScopedPointer<QDeclarativeView>(new QDeclarativeView);
#endif
QDeclarativePropertyMap binding_map;
binding_map.insert("question_txt", QVariant(QString("5 * 5 =")));
binding_map.insert("color", QVariant(QString("dark red")));
QScopedPointer<QDeclarativeContext>
binding_context(appview->rootContext());
binding_context->setContextProperty("binding_map", &binding_map);
QString file = "main.qml";
QString path = QString(DEPLOYMENT_PATH);
appview->setSource(QUrl::fromLocalFile(path + file));
appview->setResizeMode(QDeclarativeView::SizeRootObjectToView);
appview->setAttribute(Qt::WA_OpaquePaintEvent);
appview->setAttribute(Qt::WA_NoSystemBackground);
appview->viewport()->setAttribute(Qt::WA_OpaquePaintEvent);
appview->viewport()->setAttribute(Qt::WA_NoSystemBackground);
appview->showFullScreen();
binding_map["question_txt"] = QVariant(QString("overwritten 5 * 5 ="));
return myapp->exec();
}
</code>
I need to let C++ print text in the QML interface (the question) and C++
has to obtain the
answer the user has answered in the QML interface (TextField Silica
component). That's basically
the needed communication between C++ and QML.
So I thought that I'd create a QDeclarativePropertyMap in C++. This
propertymap will contain the question.
My program has a while loop that asks the user new questions each time
the loop runs(the logic code can be found here
<https://bitbucket.org/Superpelican/clamshell_cli>,
but it hasn't been adjusted for use with a GUI, it's currently a CLI
application). So I need to constantly update the QML UI from C++
while the programs running, after I've setup the QDeclarativeView etc.
However I noticed that if you change a value in the propertymap after
initializing and showing the QDeclarativeView, the UI won't be updated!
I thought the QDeclarativePropertyMap was dynamic!
http://qt-project.org/doc/qt-4.8/qdeclarativepropertymap.html#details:
"The binding is dynamic - whenever a key's value is updated, anything
bound to that key will be updated as well."
Kind Regards,
Superpelican
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