[SailfishDevel] QDeclarativePropertyMap not dynamic?

[Superpelican]

Hi everyone,

I've been looking at the PropertyChanged project again and do I need to 
use both the Q_PROPERTY stuff and the method/signals way? Or can I just 
use 1 of them?

Also do I need to make a plugin of the C++ part of my application or is 
there also another way to do it?

Kind Regards,

Superpelican


On 05/09/2013 04:30 PM, christopher.lamb at thurweb.ch wrote:
> Hi SuperPelican
>
> After a little playing around, I have created a minimal SailfishOS app 
> that demonstrates interaction between a c++ plugin and SailfishOS QML 
> UI elements.
>
> Once again I have gone the QmlRegisterType / plugin approach. The app 
> itself is the default SailfishOS QML project, with a few minor changes.
>
> The app has a SailfishOS PullDownMenu. If you click on the MenuItem 
> "increment counters", four QML labels have their values changed, each 
> by a different approach.
>
> When the MenuItem is clicked, it actually updated 2 properties, one 
> QML "FirstPage.qmlCounter"; and one "cppCounter" exposed by the C++ 
> plugin CPlusPlusCounter 1.0 (which is instantiated as a QML object 
> myCPlusPlusCounter.
>
> 1) "qml.counter binding" is a simple binding to the QML property 
> "qmlCounter" (no C++)
> 2) "qml.counter onChanged" is changed by the "onQmlCounterChanged" 
> event of the same QML property (no C++)
> 3) "myCPlusPlusCounter binding" is a binding to the property 
> "cppCounter" exposed by the C++ plugin
> 4) "myCPlusPlusCounter onChanged" is changed by the 
> "onCppCounterChanged" event of the same C++ plugin property
>
> All the QML changes are in FirstPage.qml
> C++ required minor changes to main.cpp ( qmlRegisterType entry + 
> includes)
> and the new files cpluspluscounter.h / .cpp
>
> You should find the entire project as an attachment to this post.
>
> I hope this helps
>
> Chris
>
>
> Zitat von Superpelican <superpelican at zoho.com>:
>
>> 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
>>
>>
>>