[SOLVED]which widget would be the best to display the following data?

dialingo · wrote on 8 Mar 2011, 09:16

phamtv,
Qt 4.7.1 comes with a neat tutorial which shows also how to deal with changing models.
http://doc.qt.nokia.com/4.7/modelview.html

interesting for you: 2.3, a clock inside a table cell.

phamtv · wrote on 11 Mar 2011, 17:08

dialingo/Andre/Gerolf,

I have the following code implementation, however, when I run the application, the tableview controls is shown but does not populate with the rows and columns data... Any idea what is going on? NOTE: I simplified it into 3 files...

@
// File: cls_device.h
#ifndef CLS_DEVICE_H
#define CLS_DEVICE_H

#include <QtGui>
#include <QObject>
#include <QThread>
#include <QMap>
#include <QtDebug>

struct RegData
{
QString Desc;
int Addr;
double Value;
};

class RegisterModel : public QAbstractTableModel
{
Q_OBJECT
public:
RegisterModel(){}

void setCurrencyMap(const QMap<QString, double> &map)
{
    registerMap = map;
    reset();
}

int rowCount(const QModelIndex & /* parent */) const
{
    qDebug() << registerMap.count();
    return registerMap.count();
}

int columnCount(const QModelIndex & /* parent */) const
{
    return 2; //registerMap.count();
}
Qt::ItemFlags flags(const QModelIndex & index) const
{
    if (index.column() == 0)
        return Qt::ItemIsSelectable | Qt::ItemIsEnabled ;
    else
        return Qt::ItemIsSelectable |  Qt::ItemIsEditable | Qt::ItemIsEnabled ;
}
bool setData(const QModelIndex & index, const QVariant & value, int role)
{
    if (index.isValid() && role == Qt::EditRole)
    {
        ValueAt(index.row()) = value.toString();
    }
    return true;
 }
QVariant data(const QModelIndex &index, int role) const
{
    // NOTE: int role == Qt.ItemDataRole

    if (!index.isValid())
        return QVariant();

    switch(role)
    {
    case Qt::TextAlignmentRole:
        if (index.column() == 0)
            return int(Qt::AlignLeft | Qt::AlignVCenter);
        else if (index.column() == 1)
            return int(Qt::AlignHCenter | Qt::AlignVCenter);
        else
            return QVariant();
        break;
    case Qt::DisplayRole:
        if (index.column() == 0)
            return DescAt(index.row());
        else if (index.column() == 1)
            return ValueAt(index.row());
        else
            return QVariant();
        break;
    }
    return QVariant();
}

QVariant headerData(int section, Qt::Orientation orientation, int role) const
{
    if (role != Qt::DisplayRole)
        return QVariant();

    if (orientation == Qt::Horizontal)
        return (section == 0) ? "Register" : "Value";
    else
        DescAt(section);
}

private:
QString DescAt(int offset) const
{
return (registerMap.begin() + offset).key();
}

QString ValueAt(int offset) const
{
    return QString("%1").arg((registerMap.begin() + offset).value());
}

QMap<QString, double> registerMap;

};

class cls_Device : public QThread
{
Q_OBJECT

public:
RegData* data[10];

cls_Device()
{
    for (int i = 0; i < 10; i++)
    {
        // example
        if (i == 5)
        {
            data[i] = NULL;
            continue;
        }
        data[i] = new RegData();
        data[i]->Desc = QString("Register %1").arg(i);

        qDebug() << data[i]->Desc;

        data[i]->Addr = i;
        data[i]->Value = 1;
    }
}
~cls_Device(){}   // destructor

void run()
{
    Read();
}

void Read()
{
    for (int i = 0; i < 10; i++)
    {

    }
}
void Write()
{
}

signals:

public slots:

};

#endif // CLS_DEVICE_H

// file: mainwindow.h
#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>
#include <QTableView>
#include <QLayout>
#include <cls_device.h>
#include <currencymodel.h>

//namespace Ui {
// class MainWindow;
//}

class MainWindow : public QMainWindow
{
Q_OBJECT

public:
QMap<QString, double> registerMap;
cls_Device* device;

explicit MainWindow(QWidget *parent = 0)
{
    device = new cls_Device();
    for (int i = 0; i < 10; i++)
    {
        if (device->data[i] != NULL)
            registerMap.insert(device->data[i]->Desc, device->data[i]->Value);
    }

    RegisterModel registerModel;
    registerModel.setCurrencyMap(registerMap);

    QTableView* tableView = new QTableView();
    tableView->setModel(&registerModel);
    tableView->setAlternatingRowColors(true);
    tableView->verticalHeader()->hide();
    tableView->horizontalHeader()->setStretchLastSection(true);
    tableView->resizeColumnsToContents();
    tableView->setSelectionBehavior(QAbstractItemView::SelectRows);
    setCentralWidget(tableView);

    QTimer* timer = new QTimer(this);
    timer->setInterval(1000);
    connect(timer, SIGNAL(timeout()) , this, SLOT(timerHit()));
    timer->start();
}
~MainWindow()
{
    disconnect();

    if (device != NULL)
        delete device;
}

public slots:
void timerHit()
{
}

};
#endif // MAINWINDOW_H

// File: main.cpp
#include <QObject>
#include <QtGui>
#include <mainwindow.h>

int main(int argc, char *argv[])
{
QApplication app(argc, argv);

MainWindow window;
window.showMaximized();
return app.exec();

}
@

andre · wrote on 11 Mar 2011, 17:15

You should create your model on the heap, not on the stack ( line 193 ). Now, your model is destroyed again before the data is actually shown.

giesbert · wrote on 11 Mar 2011, 17:20

Hi,

the problem is pretty easy:

you create the register model on the stack
set it to the view and then, when the c'tor goes out of scope, the model is deleted.

create the reister model on the heap as follows:

@

explicit MainWindow(QWidget *parent = 0)
{
    device = new cls_Device();
    for (int i = 0; i < 10; i++)
    {
        if (device->data[i] != NULL)
            registerMap.insert(device->data[i]->Desc, device->data[i]->Value);
    }

    RegisterModel* registerModel = new RegisterModel(this);
    registerModel->setCurrencyMap(registerMap);

    QTableView* tableView = new QTableView();
    tableView->setModel(registerModel);
    tableView->setAlternatingRowColors(true);
    tableView->verticalHeader()->hide();
    tableView->horizontalHeader()->setStretchLastSection(true);
    tableView->resizeColumnsToContents();
    tableView->setSelectionBehavior(QAbstractItemView::SelectRows);
    setCentralWidget(tableView);

    QTimer* timer = new QTimer(this);
    timer->setInterval(1000);
    connect(timer, SIGNAL(timeout()) , this, SLOT(timerHit()));
    timer->start();
}

@

aditionally, the creator of RegisterModel should look like this:

@
RegisterModel(QObject* pParent) :
QAbstractTableModel(pParent)
{
}

@

phamtv · wrote on 11 Mar 2011, 19:21

thanks Gerolf for the quick response!!!

andre · wrote on 11 Mar 2011, 19:25

-Actually, the code Gerolf presents causes a memory leak. Don't forget to give the model a parent in on line 13 of that piece of code. Candidates for parents are the form, or the view itself.-

I misread the code, there is no leak.

giesbert · wrote on 11 Mar 2011, 19:29

Andre, let me correct you.
The memory leak does not exist, as setCentralWidget reparents the widget (look at the docs) and takes the ownership.

But I also think, it looks better to give the QTableView a parent on construction....

andre · wrote on 11 Mar 2011, 19:35

I am sorry, you are right. I misread the code, and thought you did not give the model a parent. But you do. I stand corrected.

phamtv · wrote on 11 Mar 2011, 19:54

Thanks guys for your support. I have a follow up question to my model/view implementation. I added some code to spawn another thread to generate some random number, however, I don´t know how to update the table view when I receive the signal to update the table view. Can you guys give me some input? Thanks!

@
// file: cls_device.h
#ifndef CLS_DEVICE_H
#define CLS_DEVICE_H

#include <QtGui>
#include <QObject>
#include <QThread>
#include <QMap>
#include <QtDebug>

struct RegData
{
QString Desc;
int Addr;
double Value;
};

class RegisterModel : public QAbstractTableModel
{
Q_OBJECT
public:
RegisterModel(QObject* pParent) :
QAbstractTableModel(pParent){}

void setCurrencyMap(const QMap<QString, double> &map)
{
    registerMap = map;
    reset();
}

int rowCount(const QModelIndex & /* parent */) const
{
    return registerMap.count();
}

int columnCount(const QModelIndex & /* parent */) const
{
    return 2; //registerMap.count();
}
Qt::ItemFlags flags(const QModelIndex & index) const
{
    if (index.column() == 0)
        return Qt::ItemIsSelectable | Qt::ItemIsEnabled ;
    else
        return Qt::ItemIsSelectable |  Qt::ItemIsEditable | Qt::ItemIsEnabled ;
}
bool setData(const QModelIndex & index, const QVariant & value, int role)
{
    if (index.isValid() && role == Qt::EditRole)
    {
        ValueAt(index.row()) = value.toString();
    }
    return true;
 }
QVariant data(const QModelIndex &index, int role) const
{
    // NOTE: int role == Qt.ItemDataRole

    if (!index.isValid())
        return QVariant();

    switch(role)
    {
    case Qt::TextAlignmentRole:
        if (index.column() == 0)
            return int(Qt::AlignLeft | Qt::AlignVCenter);
        else if (index.column() == 1)
            return int(Qt::AlignHCenter | Qt::AlignVCenter);
        else
            return QVariant();
        break;
    case Qt::DisplayRole:
        if (index.column() == 0)
            return DescAt(index.row());
        else if (index.column() == 1)
            return ValueAt(index.row());
        else
            return QVariant();
        break;
    }
    return QVariant();
}

QVariant headerData(int section, Qt::Orientation orientation, int role) const
{
    if (role != Qt::DisplayRole)
        return QVariant();

    if (orientation == Qt::Horizontal)
        return (section == 0) ? "Register" : "Value";
    else
        DescAt(section);
}

private:
QString DescAt(int offset) const
{
return (registerMap.begin() + offset).key();
}

QString ValueAt(int offset) const
{
    return QString("%1").arg((registerMap.begin() + offset).value());
}

QMap<QString, double> registerMap;

};

class cls_Device : public QThread
{
Q_OBJECT

public:
RegData* data[10];

cls_Device()
{
    for (int i = 0; i < 10; i++)
    {
        // example
        if (i == 5)
        {
            data[i] = NULL;
            continue;
        }
        data[i] = new RegData();
        data[i]->Desc = QString("Register %1").arg(i);
        data[i]->Addr = i;
        data[i]->Value = 1;
    }
}
~cls_Device(){}   // destructor

void run()
{
    Read();
}

void Read()
{
    int min = 0;
    int max = 255;

    for (int i = 0; i < 10; i++)
    {
        double val = int( random() / (RAND_MAX + 1.0) * (max + 1 - min) + min );
        if ((data[i] != NULL) && (data[i]->Value != val))
        {
            data[i]->Value = val;
            emit RegisterValueChanged(this, data[i]);
        }
    }
}
void Write()
{
}

signals:
void RegisterValueChanged(QObject* obj, RegData* e);
public slots:

};

#endif // CLS_DEVICE_H

// file: mainwindow.h
#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>
#include <QTableView>
#include <QLayout>
#include <cls_device.h>
#include <currencymodel.h>

class MainWindow : public QMainWindow
{
Q_OBJECT

public:
QMap<QString, double> registerMap;
cls_Device* device;

explicit MainWindow(QWidget *parent = 0)
{
    device = new cls_Device();
    connect(device, SIGNAL(RegisterValueChanged(QObject*,RegData*)),
            this, SLOT(RegisterValueChanged(QObject*,RegData*)), Qt::QueuedConnection);

    for (int i = 0; i < 10; i++)
    {
        if (device->data[i] != NULL)
            registerMap.insert(device->data[i]->Desc, device->data[i]->Value);
    }

    RegisterModel* registerModel = new RegisterModel(this);
    registerModel->setCurrencyMap(registerMap);

    QTableView* tableView = new QTableView(this);
    tableView->setModel(registerModel);
    tableView->setAlternatingRowColors(true);
    tableView->verticalHeader()->hide();
    tableView->horizontalHeader()->setStretchLastSection(true);
    tableView->resizeColumnsToContents();
    tableView->setSelectionBehavior(QAbstractItemView::SelectRows);
    setCentralWidget(tableView);

    QTimer* timer = new QTimer(this);
    timer->setInterval(1000);
    connect(timer, SIGNAL(timeout()) , this, SLOT(timerHit()));
    timer->start();
}
~MainWindow()
{
    disconnect();

    if (device != NULL)
        delete device;
}

public slots:
void timerHit()
{
if (!device->isRunning())
device->start();
}

private slots:
void RegisterValueChanged(QObject* obj, RegData* e)
{
qDebug() << QString("How do I update the table view for Register address %1 with value %2").arg(e->Addr).arg(e->Value);
}
};

#endif // MAINWINDOW_H

// file main.cpp
//use the previous code snippet

@

giesbert · wrote on 11 Mar 2011, 20:03

You should start reading the "docs":http://doc.qt.nokia.com/4.7/modelview.html :-)
When you want to change a value, you have to emit a signal dataChange() and change the value before.
If you want to add/remnove rows/columns, there are also signals, which are emitted by special functions

[begin|end][insert|remove][Columns|rows]

phamtv · wrote on 11 Mar 2011, 20:17

Hi Gerolf, Thanks!, :-) I have been reading the docs but just can´t seem to connect things together. As you can see in my implementation, I have an inherited QThread class that initializes my structure pointer array. If you have noticed, I intentionally place a null pointer to register 5 because I do not have a continguous set of register in my real world scenario. QMap basically is a subset of my structure pointer array without the null pointer. I can populate the table view with RegisterModel using QMap. However, as you can see, when my thread executes, it changes the structure array value. Do I have to loop through the QMap items, compare the description strings, and then update TableView by emitting a signal dataChange()? This seem time consuming if I have loop through the QMaps items for every registers that changes.... Please advise...