[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&#40;QLatin1String("qml/myApp/main.qml"&#41;&#41;;
viewer->showExpanded();

return app->exec&#40;&#41;;

}@

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