Show live data into a table

makopo

This is my data method:

QVariant DataTableModel::data(const QModelIndex& index, int role) const
{
    if (!index.isValid()) {
        return QVariant();
    }

    if (index.row() >= m_parameter.size() && index.row() >= m_value.size()) {
        return QVariant();
    }

    if (role == Qt::DisplayRole || role == Qt::EditRole) {
        switch (index.column()) {
        case 0:
            return m_parameter.at(index.row());
            break;
        case 1:
            return m_value.at(index.row());
            break;
        default:
            Q_ASSERT(false);
        }
    }
    return QVariant();
}

JonB

@makopo
One logic fault I see is: In your insertRows() you increase the length of m_value (inserting "" into it in the new row), but you do nothing to increase the length of m_parameter correspondingly. That should mean that your data()'s return m_parameter.at(index.row()); can go wrong/crash after an insertion.

Another issue is that as you show your latest setData() it has no final, unconditional return statement at the end. This should have generated a compiler error or warning?

makopo

@JonB

Correcting this does not bring a change.

When I debug the setData() method I with the index and the values for r, c, i and m (does it mean, row, column, internal pointer and model of QmodelIndex class?) are undefined. The detailed message for r, c, i, m is "Can not read memory".

SGaist

@makopo said in Show live data into a table:

When I debug the setData() method I with the index and the values for r, c, i and m (does it mean, row, column, internal pointer and model of QmodelIndex class?) are undefined.

What are r, c, i and m ?

You should post the complete code of your model class.

By the way, you should use QAbstractModelTester to validate your implementation.

makopo

@SGaist said in Show live data into a table:

What are r, c, i and m ?

Screenshot VS

Can not recognize this error, it did not happen again...

I rewrote my model class. The values are shown in the view, but the view did not update automatically. This is the whole code:

#pragma once
#include <QAbstractTableModel>
#include <QDebug>


struct DataTableItem {

	QString m_parameter;
	QString m_value;
};

class DataTableModel : public QAbstractTableModel {

	Q_OBJECT

public:
	DataTableModel(QObject* parent = nullptr);
	DataTableModel(const QList<DataTableItem>& tableItem, QObject* parent = nullptr);

	//functions of QAbstractItemModel
	Qt::ItemFlags flags(const QModelIndex& index) const override;
	QVariant headerData(int section, Qt::Orientation orientation, int role = Qt::DisplayRole) const override;
	QVariant data(const QModelIndex& index, int role) const override;
	bool insertRows(int rows, int count, const QModelIndex& parent) override;
	bool setData(const QModelIndex& index, const QVariant& value, int role = Qt::EditRole) override;
	int rowCount(const QModelIndex& parent) const override;
	int columnCount(const QModelIndex& parent) const override;
	const QList<DataTableItem>& GetTableItem() const;

private:
	QList<DataTableItem> m_tableItem;
};

#include "DataTableModel.h"

//Ctor
DataTableModel::DataTableModel(QObject* parent)
	: QAbstractTableModel(parent) 
{}


DataTableModel::DataTableModel(const QList<DataTableItem>& tableItem, QObject* parent)
    : QAbstractTableModel(parent),
    m_tableItem(tableItem) 
{}


const QList<DataTableItem>& DataTableModel::GetTableItem() const
{
    return m_tableItem;
}


/**
* Returns the item flags for the given index. Sets the cells to editable
*/
Qt::ItemFlags DataTableModel::flags(const QModelIndex& index) const
{
    if (index.isValid())
        return Qt::ItemIsSelectable | Qt::ItemIsEnabled | Qt::ItemIsEditable;
    
    return QAbstractItemModel::flags(index);
}


/**
* Defines the header label of the table
*/
QVariant DataTableModel::headerData(int section, Qt::Orientation orientation, int role) const
{
    if (role != Qt::DisplayRole)
        return QVariant();

    if (role == Qt::DisplayRole && orientation == Qt::Horizontal) {
        switch (section) {
        case 0:
            return QString("Parameter");
            break;
        case 1:
            return QString("Wert");
            break;
        default:
            break;
        }
    }
    return QVariant();
}


/**
* Counts the number of rows which depends from the QStringList that is defined in QVideoMeter.cpp
*/
int DataTableModel::rowCount(const QModelIndex& parent) const
{
    return m_tableItem.count();
}


/**
* Defines the number of columns. This table only have two columns
*/
int DataTableModel::columnCount(const QModelIndex& parent) const
{
    return 2;
}


bool DataTableModel::insertRows(int row, int count, const QModelIndex& parent)
{
    //the following two methods emits signals that tells the view that the data should be changed
    beginInsertRows(QModelIndex(), row, row + count - 1);
    for (int i = 0; i < count; ++i)
        m_tableItem.insert(row, { QString(), QString() });
    endInsertRows();
    return true;
}


/**
* Defines the data that should be rendered to a table cell
* The QModelIndex class is used to locate data in a data model.
*/
QVariant DataTableModel::data(const QModelIndex& index, int role) const
{
    if (!index.isValid()) {
        return QVariant();
    }

    if (index.row() <0 || index.row() >= m_tableItem.count()) {
        return QVariant();
    }

    const DataTableItem& item = m_tableItem.at(index.row());
    if (role == Qt::DisplayRole || role == Qt::EditRole) {
        switch (index.column()) {
        case 0:
            return item.m_parameter;
            break;
        case 1:
            return item.m_value;
            break;
        default:
            break;
        }
    }
    return QVariant();
}


/*
* Sets the role data for the item at index to value.
*/
bool DataTableModel::setData(const QModelIndex& index, const QVariant& value, int role)
{
    if (index.isValid() && role == Qt::EditRole) {
        const int row = index.row();
        DataTableItem item = m_tableItem.value(row);

        switch (index.column()) {
        case 0:
            item.m_parameter = value.toString();
            break;
        case 1:
            item.m_value = value.toString();
            break;
        default:
            return false;
        }
        m_tableItem.replace(row, item);
        emit dataChanged(index, index, { Qt::DisplayRole, Qt::EditRole });

        return true;
    }
    return false;
}

/**
* Called when start button is clicked. Call functions of QAbstractItemModel
*/
void QVideoMeter::QAddTableContent()
{
    BSTR displayModeName; //COM data type
    QString parameters = "Framerate";
    QString values = QVariant(m_displayMode->GetWidth()).toString();

    m_tableDataModel->insertRows(0, 3, QModelIndex());
    QModelIndex index = m_tableDataModel->index(0, 0, QModelIndex());
    m_tableDataModel->setData(index, parameters, Qt::EditRole);
    index = m_tableDataModel->index(0, 1 , QModelIndex());
    m_tableDataModel->setData(index, values, Qt::EditRole);
}

It will be very friendly if someone of you can give my feedback.

JonB

@makopo
Glancing through your code looks reasonable to me. So what exactly does not work when? You say "but the view did not update automatically.". What does not happen when you do what? I assume you have checked your view is connected to this data model? Have you stepped through in debugger? Put in qDebug()s, like to ensure your emit dataChanged() is being hit?

makopo

@JonB said in Show live data into a table:

What does not happen when you do what?

QString values = QVariant(m_displayMode->GetWidth()).toString();

values get as return value the width of a video frame. The program starts with an initial value. After changing the video format and with this the width of the frame , the actual value is not shown in the table view. Instead of the new value, the old value is shown. I do the same call with qDebug() and can see that the new frame width is detected on the console.
This is also my requirement to the table view and the model: I have some function calls which detect changes on the video format and these changes should shown in the table view.

@JonB said in Show live data into a table:

I assume you have checked your view is connected to this data model?

Have I do that manually? I thought that QAbstractTableModel do the job for me.
I call m_tableView->setModel(m_tableDataModel);. Don't know if this what you mean.

@JonB said in Show live data into a table:

Put in qDebug()s, like to ensure your emit dataChanged() is being hit?

How can I test if dataChanged is called? What is the corresponding slot?
I also debug the code and found nothing.

JonB

@makopo said in Show live data into a table:

the actual value is not shown in the table view. Instead of the new value, the old value is shown.

I don't know for sure, maybe you need a fixed width or inform the view of the change or QTreeView::resizeColumnToContents(int column) or something.

Have I do that manually? I thought that QAbstractTableModel do the job for me.

I call m_tableView->setModel(m_tableDataModel);. Don't know if this what you mean.

Yes, that statement is what attaches the view to the model, it wasn't shown in your code so I didn't know if you had done it.

How can I test if dataChanged is called? What is the corresponding slot?

I also debug the code and found nothing.

What "corresponding slot"? Put a slot on it if you want to check, or just a qDebug() where your emit dataChanged(index, index, { role }); line is.

There are also QAbstractItemModel::layoutAboutToBeChanged() & QAbstractItemModel::layoutChanged() signals, I don't know if your situation might need them to tell tell the view about whatever it is that is changing.

kshegunov

To behave properly these two should look like:

int DataTableModel::rowCount(const QModelIndex& parent) const
{
    return !parent.isValid() ? m_tableItem.count() : 0;
}

int DataTableModel::columnCount(const QModelIndex& parent) const
{
    return !parent.isValid() ? 2 : 0;
}

Make sure QVideoMeter::QAddTableContent() is called. And also what exactly is m_displayMode and does QVariant know how to convert it to a string? Better use QString::number if that is some integer or something.

m_tableDataModel->insertRows(0, 3, QModelIndex());

Inserting 3 rows, but setting data for one? Are you sure?

PS:

Qt::ItemFlags DataTableModel::flags(const QModelIndex& index) const
{
    Q_ASSERT(index.isValid()); //< No calling of flags() with invalid indices!
    return QAbstractItemModel::flags(index) | Qt::ItemIsSelectable | Qt::ItemIsEnabled | Qt::ItemIsEditable;  
}

makopo

Thank you. Actually it didn't work. I try your advices, I'am searching for setting up the index, searching for the correct setup of the Widget parent, change the type for the second parameter value from QString to QVariant to int, also check if dataChanged() emits a signal (yes it does) - all that brings no change. The pasted data is shown in the view, but the parameter value doesn't update. And there is the fact that I can edit every cell of the table. And because the edited value are stored temporary I think that there is no problem with the index.
I print the values that are changing to the console, and here I can see that the ouput react to the changes. Still confusing.
Let me give you another example how I get the values (maybe there is an error):
I have a method that reads the color values of the incoming video. With this values I do a calculation and after that I send the result with a signal to the QMainClass.

redSum = CalculateAverageValue(redValues);
greenSum = CalculateAverageValue(greenValues);
blueSum = CalculateAverageValue(blueValues);

emit SendRGBAverage(redSum, greenSum, blueSum);

In the QMainClass I have a slot that stores the sended data into member variables.:

void QVideoMeter::ReceiveRGBAverage(int redSum, int greenSum, int blueSum)
{
    m_redSum = redSum;
    m_greenSum = greenSum;
    m_blueSum = blueSum;

    qDebug() << m_redSum << m_greenSum << m_blueSum;
}

The member variables I paste into the QAddTableItems() method, that is called inside QAddTableContent()

void QVideoMeter::QAddTableContent()
{
    QAddTableItems("Red", m_redSum );
}

void QVideoMeter::QAddTableItems(const QString& parameter, int& value)
{
    if (!m_tableDataModel->GetTableItem().contains({ parameter, value })) {
        m_tableDataModel->insertRows(0, 1, QModelIndex());
        m_tableDataModel->setData(m_tableDataModel->index(0, 0, QModelIndex()), parameter, Qt::EditRole);
        m_tableDataModel->setData(m_tableDataModel->index(0, 1, QModelIndex()), value, Qt::EditRole);
    }
    else {
        QStopVideo();
    }
}

But with this I get only the first transfered value, as I wrote above there is no update. On console I can see every change.
When I debug the dataChanged() signal I can see the following:
visual studio debugging result
I'am wondering about the values of the index and also about the value of m_value, because 0 is not the value the program start with. Is there an error?
This is my first big programming project. Please be kind.