Clearing elements from a QML ListView

MarkGR

I have a ListView which uses a C++ model which is populated w/data from a backstore(a SQLite db, in this case). I am now able to correctly bind the model to the view and populate the list. However, when I try to refresh the list(through a slot attached to a Button in the QML), the ListView successfully clears but I am not able to re-load any data on this or any subsequent attempts.

I am implementing QAbstractItemModel::removeRows but this does not seem to be working correctly. I suspect there may be some QML property I am missing on the ListView object, such as an index counter or something which controls this. I have confirmed that my model correctly contains data when I re-fresh the model. It is just now being displayed in the view.

My QML code is:

import QtQuick 2.12
import QtQuick.Window 2.12
import QtQuick.Controls 2.12


Rectangle {
    visible: true
    width: 640
    height: 480    
    Button {
        id: button
        x: 49
        y: 6
        text: qsTr("View Color Libraries")
        onClicked: colorLibraryViewModel.loadColorLibraries();
    }

    ColorLibrariesList {
        width: 532
        height: 324
        anchors.centerIn: parent
    }
}

import QtQuick 2.12
import QtQuick.Window 2.12
import QtQuick.Controls 2.12
import QtQuick.Layouts 1.3
import QtGraphicalEffects 1.0


ColumnLayout {
    Frame {
        Layout.fillWidth: true
        ListView {
            id: listView
            x: 49
            y: 78
            implicitWidth: 250
            implicitHeight: 250
            clip: true            
            model: colorLibraryListModel
            delegate: RowLayout {
                width: parent.width
                Text {
                    text: name
                }
                Image {                    
                    source: type
                }
                Text {                    
                    text: isReadOnly
                }
         }
     }
    }
}

My view/model class, as I call it(which handles the binding of my model to the QQmlContext), is defined and implemented as such:

#ifndef COLORLIBRARYVIEWMODEL_H
#define COLORLIBRARYVIEWMODEL_H

#include <QObject>
#include <QQuickView>
#include "datasourceinterface.h"
#include "ColorLibraryListModel.h"

class ColorLibraryViewModel : public QObject
{
    Q_OBJECT
public:
     ColorLibraryViewModel(QQmlContext* ctxt, DataSourceInterface *dataSource);
     ColorLibraryViewModel(){}
    Q_INVOKABLE void loadColorLibraries();

signals:
     //void librariesLoaded();

public slots:

private:
     DataSourceInterface * _DataSource;
     QQmlContext * _ctxt;
     ColorLibraryListModel _colorLibraryListModel;
     void initialize();

};

#endif // COLORLIBRARYVIEWMODEL_H

#include "colorlibraryviewmodel.h"
#include "colorlibrariesform.h"
#include "ColorLibraryListModel.h"
#include "generallistitem.h"
#include "datasourceinterface.h"
#include <QQmlContext>

ColorLibraryViewModel::ColorLibraryViewModel(QQmlContext *ctxt, DataSourceInterface *dataSource)
{
    _DataSource = dataSource;
    _ctxt = ctxt;
    initialize();
}

void ColorLibraryViewModel::initialize()
{
    _ctxt->setContextProperty("colorLibraryListModel", &_colorLibraryListModel);
}

void ColorLibraryViewModel::loadColorLibraries()
{
    ColorLibrariesForm colorLibrariesForm;
    colorLibrariesForm.Initialize(_DataSource, false, false);
    QVector<GeneralListItem> m_generalListItems;
    colorLibrariesForm.GetListItems(m_generalListItems);

    // Clear any previously loaded data
    if(_colorLibraryListModel.rowCount() > 0)
     _colorLibraryListModel.removeRows(0, _colorLibraryListModel.rowCount());


    foreach(GeneralListItem m_generalListItem, m_generalListItems){
        QIcon type = QIcon(":Images/Images/Color_Libraries_button.png") ;
        QString name = m_generalListItem._Name;
        bool isReadOnly = m_generalListItem._IsReadOnly;
        StandardDisplayItem m_standardDisplayItem(type, name, isReadOnly);
        _colorLibraryListModel.addStandardDisplayItem(m_standardDisplayItem);
    }
}

My model which is actually bound to the ListView is defined and implemented as such:

#ifndef COLORLIBRARYLISTMODEL_H
#define COLORLIBRARYLISTMODEL_H

#include <QObject>
#include <QAbstractListModel>
#include <QStringList>
#include <StandardDisplayItem.h>


class ColorLibraryListModel : public QAbstractListModel
{
    Q_OBJECT
public:
    enum ColorLibraryRoles {
        NameRole,
        TypeRole,
        IsReadOnlyRole
    };

    ColorLibraryListModel(QObject *parent = nullptr);

    void addStandardDisplayItem(const StandardDisplayItem &standardDisplayItem);

    void clearStandardDisplayItems(){m_standardDisplayItems.clear();}

    Qt::ItemFlags flags(const QModelIndex &index);

    int rowCount(const QModelIndex & parent = QModelIndex()) const;

    QVariant data(const QModelIndex & index, int role = Qt::DisplayRole) const;

    bool removeRows(int row, int count, const QModelIndex &parent = QModelIndex());

signals:

public slots:

protected:
    QHash<int, QByteArray> roleNames() const;

private:
    QList<StandardDisplayItem> m_standardDisplayItems;
};

#endif // COLORLIBRARYLISTMODEL_H

#include "ColorLibraryListModel.h"
#include <QAbstractListModel>

ColorLibraryListModel::ColorLibraryListModel(QObject *parent)
    : QAbstractListModel(parent)
{

}

QHash<int, QByteArray>ColorLibraryListModel::roleNames() const {
    QHash<int, QByteArray> roles;
    roles[NameRole]= "name";
    roles[TypeRole] = "type";
    roles[IsReadOnlyRole] = "isReadOnly";
    return roles;
}

void ColorLibraryListModel::addStandardDisplayItem(const StandardDisplayItem &standardDisplayItem)
{
    beginInsertRows(QModelIndex(), rowCount(), rowCount());
    m_standardDisplayItems << standardDisplayItem;
    endInsertRows();
}

int ColorLibraryListModel::rowCount(const QModelIndex &parent) const
{
    Q_UNUSED(parent);
    return m_standardDisplayItems.count();
}

QVariant ColorLibraryListModel::data(const QModelIndex &index, int role) const
{
    if(!index.isValid())
        return QVariant();
    if(index.row() < 0 || index.row() >= m_standardDisplayItems.count())
        return QVariant();

    const StandardDisplayItem &standardDisplayItem = m_standardDisplayItems[index.row()];
    if(role == NameRole)
        return standardDisplayItem._name();
    else if(role == TypeRole)
        return standardDisplayItem._type();
    else if(role == IsReadOnlyRole)
        return standardDisplayItem._isReadOnly() ? QString("Yes") : QString("No");
    return QVariant();
}

bool ColorLibraryListModel::removeRows(int row, int count, const QModelIndex &parent)
{
    Q_UNUSED(parent)
    beginRemoveRows(QModelIndex(), row, row+count-1);

    for(int currentRow=0; currentRow < count; ++currentRow) {
        m_standardDisplayItems.removeAt(currentRow);
    }

    endRemoveRows();
    return true;
}

The process is initiated through a main.cpp implementation as such:

#include <QGuiApplication>
#include <QQmlApplicationEngine>
#include <QQmlContext>
#include <QtQuick>
#include "colorlibraryviewmodel.h"
#include "ColorLibraryListModel.h"
#include "colorlibrariesform.h"
#include "DBsource.h"
#include "GeneralListDetailForm.h"


int main(int argc, char *argv[])
{
    QCoreApplication::setAttribute(Qt::AA_EnableHighDpiScaling);

    QGuiApplication app(argc, argv);

    QQuickView view;
    view.setResizeMode(QQuickView::SizeRootObjectToView);
    QQmlContext *ctxt = view.rootContext();

    DBSource m_dbSource;
    ColorLibraryViewModel colorLibraryViewModel(ctxt, &m_dbSource);

    ctxt->setContextProperty("colorLibraryViewModel", &colorLibraryViewModel);

    view.setSource(QUrl("qrc:/main.qml"));
    view.show();

    return app.exec();
}

Does anyone spot the problem based on my implementation? Many thanks in advance!

Unsolved Clearing elements from a QML ListView