Deselect lines in table views

[miraks]

Hi,

I would like to implement the following behavior on my QTableView:
left clicking in a blank area should act as "deselect" (any selected line should be unselected).

Do you know how to implement this ?

Thank you in advance.

[jpn]

Reimplement mousePressEvent(), check event button & itemAt(), and if it returns null, call clearSelection().

[miraks]

Reimplement mousePressEvent(), check event button & itemAt(), and if it returns null, call clearSelection().

Hi jpn,

Thank you for your help, I did it like this:

void SKGTableView::mousePressEvent ( QMouseEvent * event )
{
        if (event->button()==Qt::LeftButton && !(this->indexAt(event->pos()).isValid())) {
                clearSelection();
        }
        QTableView::mousePressEvent(event);
}

void SKGTableView::mousePressEvent ( QMouseEvent * event )
{
        if (event->button()==Qt::LeftButton && !(this->indexAt(event->pos()).isValid())) {
                clearSelection();
        }
        QTableView::mousePressEvent(event);
}

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It works as expected !

[kremuwa]

To reimplement (for example) mousePressEvent I have to subclass QTableWidget/View at first, right? And I won't be able to position it via Qt Designer?

[Lykurg]

To reimplement (for example) mousePressEvent I have to subclass QTableWidget/View at first, right?

Right.

And I won't be able to position it via Qt Designer?

Sure you are. Use the promote option in designer. Or of course write a custom plugin...

[kremuwa]

Could you expand a little bit this "promote" option? All of the widgets in my app are created using Qt Designer and I don't want to change it now.

[Lykurg]

right click on any widget in your designer and then you have the option (above goto slot) promote to. There you can say, that your own class should be used.

[kremuwa]

I have prepared such a class:

class upgTableWidget : public QTableWidget
{
    void mouseReleaseEvent(QMouseEvent *event)
    {
        if(event->button() == Qt::LeftButton && !(this->indexAt(event->pos()).isValid()))
            this->clearSelection();
        QTableWidget::mouseReleaseEvent(event);
    }
};

class upgTableWidget : public QTableWidget
{
    void mouseReleaseEvent(QMouseEvent *event)
    {
        if(event->button() == Qt::LeftButton && !(this->indexAt(event->pos()).isValid()))
            this->clearSelection();
        QTableWidget::mouseReleaseEvent(event);
    }
};

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...in a separate *.h file. I used that "Promote to..." option and I got such errors, coming from "ui_mainwindow.h" file (mainwindow is the class of the window where this table is placed):

C:/Users/K1/Desktop/Dengo - Projekt/mainwindow.h:4: In file included from mainwindow.h:4,
C:/Users/K1/Desktop/Dengo - Projekt/mainwindow.cpp:1: from mainwindow.cpp:1:
C:/Users/K1/Desktop/Dengo - Projekt/ui_mainwindow.h:174: error: no matching function for call to 'upgTableWidget::upgTableWidget(QWidget*&)'
C:/Users/K1/Desktop/Dengo - Projekt/./upgtablewidget.h:8: note: candidates are: upgTableWidget::upgTableWidget()
C:/Users/K1/Desktop/Dengo - Projekt/./upgtablewidget.h:8: note: upgTableWidget::upgTableWidget(const upgTableWidget&)

I tried to change the constructor call to the one without any arguments and it worked, but I think that if I change something in the GUI I'll have to regenerate the ui_ file and the error will show up again. What do you think about it, maybe I should ensure additional constructor in my class?

I've got another problem, too. As I said before, the tables (yes, there are two tables and I want both of them to be of type upgTableWidget) are placed on the window of class MainWindow which is a subclass of QMainWindow. When I click on one of the tables, if the second one was selected, I want to clearSelection in the second table. My problem is, that I don't know how to access the second table - it should be probably made with some kind of parent and it may be something related to the first problem.

Thanks in advance for any advices,
Michał

[Lykurg]

Simple provide a standard constructor taking a QWidget as parent and pass it to the QTableWidget base class.

upgTableWidget(QWidget *parent = 0) : QTableWidget(parent) {}

upgTableWidget(QWidget *parent = 0) : QTableWidget(parent) {}

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[kremuwa]

Ok, it works... But what exactly is passed do the parent object? How can I access the second table placed on the same window to clear it's selection?

[Lykurg]

Ok, it works... But what exactly is passed do the parent object?

the parent.

How can I access the second table placed on the same window to clear it's selection?

What second table?

[kremuwa]

I've got mainwindow.ui file which contains QMainWindow object with two tables of type upgTableWidget placed on it. Currently, when there is a selection in the first table and I click an item of the second one, I have two selections at the same time (the first one loses focus but it's still selected). What I want to do is to have only one selection at the same time. So I thought, that in the reimplemented mouseReleaseEvent() function I'll clear the selection of the table previously selected. But to do that, I have to access it somehow. The question is, how to do that.

You must be really irritated because of my silliness, but hold on a little longer.

[Lykurg]

Use signal and slots. Try something like that:

QTableWidget w1;
    w1.setRowCount(5);
    w1.setColumnCount(3);
 
    QTableWidget w2;
    w2.setRowCount(5);
    w2.setColumnCount(3);
 
    for(int row = 0; row < 5; ++row)
    {
        for(int column = 0; column < 3; ++column)
        {
            QTableWidgetItem *newItem = new QTableWidgetItem(QString("%1").arg((row+1)*(column+1)));
            w1.setItem(row, column, newItem);
        }
    }
 
    for(int row = 0; row < 5; ++row)
    {
        for(int column = 0; column < 3; ++column)
        {
            QTableWidgetItem *newItem = new QTableWidgetItem(QString("%1").arg((row+1)*(column+1)));
            w2.setItem(row, column, newItem);
        }
    }
 
    QWidget w;
    QHBoxLayout l;
    l.addWidget(&w1);
    l.addWidget(&w2);
    w.setLayout(&l);
    w.show();
 
    QObject::connect(&w1, SIGNAL(currentItemChanged(QTableWidgetItem*,QTableWidgetItem*)), &w2, SLOT(clearSelection()));

QTableWidget w1;
    w1.setRowCount(5);
    w1.setColumnCount(3);

    QTableWidget w2;
    w2.setRowCount(5);
    w2.setColumnCount(3);

    for(int row = 0; row < 5; ++row)
    {
        for(int column = 0; column < 3; ++column)
        {
            QTableWidgetItem *newItem = new QTableWidgetItem(QString("%1").arg((row+1)*(column+1)));
            w1.setItem(row, column, newItem);
        }
    }

    for(int row = 0; row < 5; ++row)
    {
        for(int column = 0; column < 3; ++column)
        {
            QTableWidgetItem *newItem = new QTableWidgetItem(QString("%1").arg((row+1)*(column+1)));
            w2.setItem(row, column, newItem);
        }
    }

    QWidget w;
    QHBoxLayout l;
    l.addWidget(&w1);
    l.addWidget(&w2);
    w.setLayout(&l);
    w.show();

    QObject::connect(&w1, SIGNAL(currentItemChanged(QTableWidgetItem*,QTableWidgetItem*)), &w2, SLOT(clearSelection()));

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But be aware that this is just a demonstration. You have to make a own slot, from where you clear the table widgets and make sure that you don't get a infinite loop. To know which table widget calls the slot use QTableWidgetItem::tableWidget().