[SOLVED] Read/write user settings

[strekazoid]

I need to save and read user settings for my QML application What would be the best way to do so? Some text/xml file? Is it possible to create/read/write text files from QML?

[lgeyer]

I usually expose a QSettings object from C++.

[strekazoid]

Thanks. So the scenario is to implement a method in main.cpp for reading / writing settings, and call it from QML side?

[lgeyer]

More or less. I use a thin wrapper around QSettings and expose it through a context property.
@
// settings.h

class Settings : public QSettings
{
Q_OBJECT

public:
explicit Settings(QObject *parent = 0) : QSettings(QSettings::IniFormat,
QSettings::UserScope,
QCoreApplication::instance()->organizationName(),
QCoreApplication::instance()->applicationName(),
parent) {}

Q_INVOKABLE inline void setValue(const QString &key, const QVariant &value) { QSettings::setValue(key, value); }
Q_INVOKABLE inline QVariant value(const QString &key, const QVariant &defaultValue = QVariant()) const { return QSettings::value(key, defaultValue); }

};

Q_DECLARE_METATYPE(Settings*)

// main.cpp

QScopedPointer<QApplication> application(new QApplication(argc, argv));
Settings* settings = new Settings(application.data());

QScopedPointer<QDeclarativeView> mainWindow(new QDeclarativeView);
mainWindow->rootContext()->setContextProperty("Settings", settings);

// MainWindow.qml

Rectangle {
id: sidebarContent
width: Settings.value("desktop/MainWindow.sidebar.width", 200);
...
onReleased: {
Settings.setValue("desktop/MainWindow.sidebar.width", sidebarContent.width);
}
}

@

[strekazoid]

Getting some troubles. Can you spot what is wrong here? I'm getting error: invalid use of incomplete type 'struct QDeclarativeContext' on line 12:

main.cpp
@#include <QtGui/QApplication>
#include "qmlapplicationviewer.h"
#include "settings.h"

Q_DECL_EXPORT int main(int argc, char *argv[])
{
QScopedPointer<QApplication> app(createApplication(argc, argv));
QScopedPointer<QmlApplicationViewer> viewer(QmlApplicationViewer::create());

// Attaching QSettings wrapper and exposing it to our QML UI
Settings* settings = new Settings(app.data());
viewer->rootContext()->setContextProperty("Settings", settings);

viewer->setMainQmlFile(QLatin1String("qml/myApp/main.qml"));
viewer->showExpanded();

return app->exec();

}@

The only difference here with your code is that currently wizard generated code contains QmlApplicationViewer instance instead of QDeclarativeView (like in your code).

[lgeyer]

You haven't included <QtGui/QDeclarativeContext>.

[strekazoid]

Thanks a lot, works now!

[lgeyer]

You're welcome. If the problem has been solved for you feel free to edit your initial post title and prepend "[Solved]" to it to indicate that there is a solution inside.

[strekazoid]

Hey, is there some way to save image to settings? I have path to the image, how do I save it now to Settings?

[Rahul Das]

Try this :
@settings.setValue("General/Pixmap", pixmap ); // pxmap is QPixmap@

I haven't tried it yet, let me knw whats happening :)

[strekazoid]

Thanks. How do I construct QPixmap in QML?

[Rahul Das]

"here":http://doc.qt.nokia.com/latest/qdeclarativeimageprovider.html

[strekazoid]

I'm still sort of confused. Is it possible to construct QPixmap in QML layer, or do I have to do something on C++ side as well?

[Rahul Das]

A request from QML for image/pixmap is handled by the 'Image Provider ' class, in simple words.

Yes you have to implement the Image provider in C++.

[strekazoid]

Ok, thanks, I'll try to play with this idea.

[Jon Heron]

Thank you for this excellent post!!
Cheers,
Jon

[Traxx]

Is the wrapper suppose to work out of the box and how do i make it work without qscopedpointer? Thank you

EDIT : Created a proper solution so anyone can answer to help future member