qml listview does not update information after datachanged() signal - c++

Question

I have a model written based on this example. This model is connected to a listview to display dynamic data. I have made sure the model's datachanged() signal is emitted whenever the source data is being changed. The list view does not update on the datachanged() signal. Here is my code:
DataModel.h:
class DataList {
public:
DataList(const QString &name, const QString &value, const QString &category);
QString name() const;
QString value() const;
QString category() const;
private:
QString m_name;
QString m_value;
QString m_category;
};
class DataModel : public QAbstractListModel {
Q_OBJECT
public:
enum AVRoles {
NameRole = Qt::UserRole + 1,
ValueRole,
CategoryRole
};
DataModel(QAbstractItemModel *parent = 0);
virtual ~DataModel() {}
void addData(const DataList &datalist);
int rowCount(const QModelIndex & parent = QModelIndex()) const;
QVariant data(const QModelIndex & index, int role=Qt::DisplayRole) const;
protected:
QHash<int, QByteArray> roleNames() const;
private:
QList<DataList> m_datalist;
public slots:
void onInitialPolygonAreaChanged(qreal);
};
DataModel.cpp:
DataList::DataList(const QString &name, const QString &value, const QString &category) {
m_name = name;
m_value = value;
m_category = category;
}
QString DataList::name() const {
return m_name;
}
QString DataList::value() const {
return m_value;
}
QString DataList::category() const {
return m_category;
}
DataModel::DataModel(QAbstractItemModel *parent) :
QAbstractListModel(parent) {
}
void DataModel::addData(const DataList &datalist){
beginInsertRows(QModelIndex(), rowCount(), rowCount());
m_datalist << datalist;
endInsertRows();
}
int DataModel::rowCount(const QModelIndex &parent) const{
Q_UNUSED(parent);
return m_datalist.count();
}
QVariant DataModel::data(const QModelIndex &index, int role) const {
if (index.row() < 0 || index.row() >= m_datalist.count())
return QVariant();
const DataList &datalist = m_datalist[index.row()];
if(role ==NameRole )
return datalist.name();
else if(role == ValueRole)
return datalist.value();
else if(role == CategoryRole)
return datalist.category();
return QVariant();
}
QHash<int, QByteArray> DataModel::roleNames() const {
QHash<int, QByteArray> roles;
roles[NameRole] = "name";
roles[ValueRole] = "value";
roles[CategoryRole] = "category";
return roles;
}
void DataModel::onInitialPolygonAreaChanged(qreal ) {
//0 is the index of iPA
qDebug() << "IPA from model" ;
QVector<int> roleVector;
roleVector.append(ValueRole);
roleVector.append(NameRole);
roleVector.append(CategoryRole);
roleVector.append(Qt::DisplayRole);
emit dataChanged(index(0),index(0),roleVector);
}
Mainwindow.cpp:
model.addData(DataList(QString("Initial Polygon Area"),QString::number(av1.initialPolygonArea()) + " sq.km",QString("Area")));
View->rootContext()->setContextProperty("AVModel",&model);
connect(&av1,SIGNAL(initialPolygonAreaChanged(qreal)),&model,SLOT(onInitialPolygonAreaChanged(qreal)));
view.qml:
ListView {
id: view
anchors.top: parent.top
anchors.bottom: parent.bottom
width: parent.width
model: AVModel
delegate: Text { text: name + " " + value; font.pixelSize: 18 ; color: "white"}
}