ListView doesn't update after changing data in QStringListModel

David_Gil

Hi!

I'm writing a program to show in real time the position of the planets in the ecliptic.

First, I have a ListView:

@
import QtQuick 2.0

Item {
width: 200
height: 400

ListView {
    width: parent.width; height: 300
    id: listView
    anchors.fill: parent
    highlight: Rectangle { color: "lightsteelblue"; radius: 5 }
    focus: true
    model: myModel
    delegate: Rectangle {
        height: 20
        width: parent.width
        Text {
            text: display
            font.pointSize: 12
        }
    }
}

}
@

Then, I have a QStringListModel:
@
class QalPlanetGroup;
class QStringListModel;

#include "qtquick2applicationviewer.h"

class Viewer : public QtQuick2ApplicationViewer
{
Q_OBJECT
public:
Viewer();

public slots:
void update();

private:
QalPlanetGroup *planetGroup;
QStringListModel *model;
};
@

As you can see in the following code, the data updates every second and every row is checked. If the position of the planet has changed, it sets the model's row data. The problem is that the ListView doesn't update, it keeps showing the same initial data, and I don't know what to change to make it update it. In fact, I have the same program made of QWidgets and works perfectly well, but I want to port it to QML to be able to use it in my mobile phone.

@
#include <QStringListModel>
#include <QQuickView>
#include <QQmlContext>
#include <QTimer>

#include <qalplanetgroup.h>

#include "viewer.h"

#include <QDebug>

Viewer::Viewer()
{
model = new QStringListModel;
planetGroup = new QalPlanetGroup;
planetGroup->addMainPlanets();
planetGroup->computeData();

QDateTime dateTime = QDateTime::currentDateTimeUtc();

planetGroup->computeData(dateTime);
QStringList l = planetGroup->toStringList("%n:\t

sierdzio

This is expected behaviour. See the "documentation":http://qt-project.org/doc/qt-5.0/qtquick/qtquick-modelviewsdata-cppmodels.html:
[quote]Note: There is no way for the view to know that the contents of a QStringList have changed. If the QStringList changes, it will be necessary to reset the model by calling QQmlContext::setContextProperty() again.[/quote]

David_Gil

Hi sierdzio,

That's true for QStringList-based models and QObjectList-based models. But in this case I'm dealing with QStringListModel, a QAbstractItemModel subclass. In the third section of the page you mention:

bq. QML views are automatically updated when the model changes. Remember the model must follow the standard rules for model changes and notify the view when the model has changed by using QAbstractItemModel::dataChanged(), QAbstractItemModel::beginInsertRows(), and so on. See the Model subclassing reference for more information.

The thing is that the model automatically notifies the changes (as a QAbstractItemModel subclass) but for some reason it doesn't take effect.

Thank you for your reply, anyway :-)