Using QSortFilterProxyModel - qt

Question

Please have a look into the following code:
CMyModel* myModel = new CMyModel(); //This is my main model sub-classing QAbstractListItemModel
CMySortModel* mySortModel = new CMySortModel(); //This is my sort filter proxy model sub-classing QSortFilterProxyModel
mySortModel->setSourceModel(myModel);
mySortModel->setDynamicSortFilter(true);
mySortModel->setSortRole(CMyModel::displayRole);
myModel->Initialize(); // This is working fine
mySortModel->sort(0);
// myModel->Initialize(); // This is not working
The above code is working fine when the data structure (basically a QList of integers linked to CMyModel) is initialized before, mySortModel->sort(0) is called.
If the list is initialized after the sort method call, the view is basically not showing any data.
Then I tried following
mySortModel->sort(0);
myModel->Initialize();
mySortModel->Invalidate(); // This is working fine.
But realized that, every time there is an update in the QList, I need to call mySortModel->Invalidate() to update my view. Otherwise the view is not updating. This is causing a complete view update and in turn a flickering in my screen.
As not much idea on Qt/QML model view coding, so bit stuck with the issue.
Please correct me, if I am doing anything wrong.
MyModel.cpp
#include "MyModel.h"
#include <QDateTime>
CMyModel::CMyModel(QObject *parent)
: QAbstractListModel(parent)
{
m_mapRoles.insert(rolesEnum::displayRole, "displayRole");
}
void CMyModel::Initialize()
{
qsrand(QDateTime::currentMSecsSinceEpoch() / 1000);
quint32 index = 0;
while (index < 200)
{
m_lstOfInts.append(qrand() % 1000);
index++;
}
}
int CMyModel::rowCount(const QModelIndex &parent) const
{
Q_UNUSED(parent)
return m_lstOfInts.count();
}
int CMyModel::columnCount(const QModelIndex &parent) const
{
Q_UNUSED(parent)
return 1;
}
QVariant CMyModel::data(const QModelIndex &index, int role) const
{
Q_UNUSED(role)
int rowVal = index.row();
if (role == rolesEnum::displayRole)
{
if (rowVal >= 0 && rowVal < m_lstOfInts.count())
{
return m_lstOfInts.at(rowVal);
}
}
return QVariant();
}
QHash<int, QByteArray> CMyModel::roleNames() const
{
return m_mapRoles;
}
MyModel.h
#ifndef MYMODEL_H
#define MYMODEL_H
#include <QAbstractListModel>
#include <QObject>
#include <QHash>
class CMyModel : public QAbstractListModel
{
Q_OBJECT
public:
enum rolesEnum {
displayRole
};
Q_ENUM(rolesEnum)
public:
explicit CMyModel(QObject *parent = NULL);
// QAbstractItemModel interface
public:
int rowCount(const QModelIndex &parent) const;
int columnCount(const QModelIndex &parent) const;
QVariant data(const QModelIndex &index, int role) const;
private:
QList<int> m_lstOfInts;
QHash<int, QByteArray> m_mapRoles;
// QAbstractItemModel interface
public:
QHash<int, QByteArray> roleNames() const;
void Initialize();
};
#endif // MYMODEL_H
MySortModel.cpp
#include "MySortModel.h"
#include "MyModel.h"
CMySortModel::CMySortModel(QObject *parent)
: QSortFilterProxyModel(parent)
{
}
bool CMySortModel::lessThan(const QModelIndex &source_left, const QModelIndex &source_right) const
{
return sourceModel()->data(source_left, CMyModel::displayRole).toInt() < sourceModel()->data(source_right, CMyModel::displayRole).toInt();
}
MySortModel.h
#ifndef MYSORTMODEL_H
#define MYSORTMODEL_H
#include <QSortFilterProxyModel>
class CMySortModel : public QSortFilterProxyModel
{
public:
explicit CMySortModel(QObject* parent = NULL);
// QSortFilterProxyModel interface
protected:
bool lessThan(const QModelIndex &source_left, const QModelIndex &source_right) const;
};
#endif // MYSORTMODEL_H
main.cpp
#include <QGuiApplication>
#include <QQmlApplicationEngine>
#include <QQuickView>
#include <QQmlContext>
#include "MyModel.h"
#include "MySortModel.h"
int main(int argc, char *argv[])
{
#if defined(Q_OS_WIN)
QCoreApplication::setAttribute(Qt::AA_EnableHighDpiScaling);
#endif
QGuiApplication app(argc, argv);
qmlRegisterType<CMySortModel>("CMySortModel", 1, 0, "CMySortModel");
CMyModel* myModel = new CMyModel();
CMySortModel* mySortModel = new CMySortModel();
mySortModel->setSourceModel(myModel);
mySortModel->setDynamicSortFilter(true);
mySortModel->setSortRole(CMyModel::displayRole);
// myModel->Initialize(); // This works
mySortModel->sort(0);
myModel->Initialize(); // This works when followed by a invalidate call on the proxy model
mySortModel->invalidate();
QQmlApplicationEngine engine;
engine.rootContext()->setContextProperty("_myModel", mySortModel);
engine.load(QUrl(QStringLiteral("qrc:/main.qml")));
if (engine.rootObjects().isEmpty())
{
delete mySortModel;
mySortModel = NULL;
delete myModel;
myModel = NULL;
return -1;
}
return app.exec();
}
main.qml
import QtQuick 2.9
import QtQuick.Window 2.2
import QtQuick.Layouts 1.3
import QtQuick.Controls 2.2
import QtGraphicalEffects 1.0
Window {
id: window
visible: true
width: 800
height: 480
title: qsTr("Hello World")
ScrollView {
anchors.fill: parent
width: parent.width
GridView {
anchors.fill: parent
//columns: 2
model: _myModel
delegate: Text {
id: _text
text: model.displayRole
}
}
}
}
Modified Initialize method as follows and it is working now
void CMyModel::Initialize()
{
qsrand(QDateTime::currentMSecsSinceEpoch() / 1000);
quint32 index = 0;
while (index < 200)
{
beginInsertRows(QModelIndex(), m_lstOfInts.size(), m_lstOfInts.size());
m_lstOfInts.append(qrand() % 1000);
index++;
endInsertRows();
}
}