How to display data inside QtTableView from a Model

Question

I am new to Qt5 and trying to create a QTableView widget using QtCreator. As for as I understand QTableView can be connected to a model via a setModel method and Model must be an instance QtAbstractTableModel

#ifndef FILELIST_H
#define FILELIST_H
#include <QAbstractTableModel>
namespace Ui {
    class FileList;
}

class FileList : public QAbstractTableModel
{
    Q_OBJECT
public:
    FileList(QObject *parent=nullptr);
    int rowCount(const QModelIndex &parent = QModelIndex()) const override;
    int columnCount(const QModelIndex &parent = QModelIndex()) const override;
    QVariant data(const QModelIndex &index, int role = Qt::DisplayRole) const override;

};

#endif // FILELIST_H

Here is the Implementation FileList.cpp

#include <QFont>
#include <QBrush>
#include <QDebug>
#include "FileList.h"

FileList::FileList(QObject *parent) : QAbstractTableModel(parent)
{
    qDebug() << QString("Constructor...");
}

int FileList::rowCount(const QModelIndex &parent) const
{
    return 2;
}

int FileList::columnCount(const QModelIndex &parent) const
{
    return 3;
}

QVariant FileList::data(const QModelIndex &index, int role) const
{
    int row = index.row();
        int col = index.column();
        // generate a log message when this method gets called
        qDebug() << QString("row %1, col%2, role %3")
                .arg(row).arg(col).arg(role);

        switch (role) {
        case Qt::DisplayRole:
            if (row == 0 && col == 1) return QString("<--left");
            if (row == 1 && col == 1) return QString("right-->");

            return QString("Row%1, Column%2")
                    .arg(row + 1)
                    .arg(col +1);
        case Qt::FontRole:
            if (row == 0 && col == 0) { //change font only for cell(0,0)
                QFont boldFont;
                boldFont.setBold(true);
                return boldFont;
            }
            break;
        case Qt::BackgroundRole:
            if (row == 1 && col == 2)  //change background only for cell(1,2)
                return QBrush(Qt::red);
            break;
        case Qt::TextAlignmentRole:
            if (row == 1 && col == 1) //change text alignment only for cell(1,1)
                return Qt::AlignRight + Qt::AlignVCenter;
            break;
        case Qt::CheckStateRole:
            if (row == 1 && col == 0) //add a checkbox to cell(1,0)
                return Qt::Checked;
            break;
        }
        return QVariant();
}

Now when I attach the QTableView widget to my main window the data does not show up in the table view and I get a blank empty TableView

CloudSync.cpp

#include <QDebug>
#include "CloudSync.h"
#include "ui_cloudsync.h"
#include "FileList.h"

CloudSync::CloudSync(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::CloudSync)
{
    ui->setupUi(this);
    FileList fileList;
    qDebug() << QString("row %1, col%2, role %3");
    ui->listView->setModel(&fileList);
    //ui->listView->show();
    setCentralWidget(ui->listView);

}

CloudSync::~CloudSync()
{
    delete ui;
}

and main.cpp

#include "CloudSync.h"
#include <QApplication>

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    CloudSync w;
    w.show();

    return a.exec();
}

Now what I am doing wrong here? The qDebug inside the ::data method does not output anything into the console which makes me the thing that the model is not properly connected

Final Output

change `FileList fileList;` to `FileList *fileList; = new FileList(this);` and change `ui->listView->setModel(&fileList);` to `ui->listView->setModel(fileList);` — eyllanesc, Jul 24 '19 at 21:06
It worked now thanks, two things here 1) I was passing it by reference and now passing a pointer what is the difference? 2) Do I now need to delete the fileList manually to clean up the memory? — Aftab Naveed, Jul 24 '19 at 21:12
1) In your initial code and my suggestion you are passing a pointer, the problem is not how you pass the model in sight but the model is a local variable that will be eliminated when the constructor is finished executing. 2) In Qt, QObjects can handle the life cycle of other variables, in this case the parents of a QObject eliminate their children when they are eliminated, with my suggestion CloudSync is the parent of the model (passed as the parent of the model to this ) so it is not necessary to remove it manually since Qt will do it for you. — eyllanesc, Jul 24 '19 at 21:17

How to display data inside QtTableView from a Model

0 Answers0