Qt - Centering a checkbox in a QTable

Question

In QtCreater I added a table to my project. in my code I am generating some data to output into the table. I want to add a QCheckbox into each row to allow the row to be selected. All the content of the table is aligned left, how do I make only these checkboxes in the first column of every row align to the center?

I'm adding the QCheckbox using:

ui->data_table->setCellWidget(rowCount,0, new QCheckBox);

Lauder

Answer 1

I usually use a layout and a container widget for this. It is an ugly solution, but it works:

QWidget * w = new QWidget();
QHBoxLayout *l = new QHBoxLayout();
l->setAlignment( Qt::AlignCenter );
l->addWidget( <add your checkbox here> );
w->setLayout( l );
ui->data_table->setCellWidget(rowCount,0, w);

So basically you will have:

Table Cell -> Widget -> Layout -> Checkbox

you'll have to consider it if you will need to access the checkbox through the table.

Bekha

It seems like something that should be much easier then that. I was looking through docs for a long time trying to find a function or something that did what I wanted. But what you posted works perfectly, I would of never figured that out on my own though. Thanks! – Lauder

@SingerOfTheFall, how to get the checkstatus of the checkbox? – Stuckup

Alignment is perfect here. It's not when using stylesheet proposed by other answers (where checkbox ends up shifted to the right by some pixels). – Emprise

Answer 2

Two thumbs up for Barry Mavin! You don't even have to subclass.

one line...

pCheckBox->setStyleSheet("margin-left:50%; margin-right:50%;");

done!!

Orography

Answer 3

This is an old post but in fact there is a much easier and lighter way of achieving this, just subclass QCheckBox and set the stylesheet to

margin-left:50%;
margin-right:50%;

Rockandroll

Im in PyQt4 and this only works when setting the initial value. That is, if I resize the column it does not continue to center the checkbox, it only centers it when it is first created. – Sequoia

Answer 4

It works for me, but my checkbox is not completely displayed.

To have a complete view of the widget, remove margins in layout :

l->setContentsMargins(0,0,0,0);

Ackley

Answer 5

As stated in similar question around Stack Overflow, it's currently an open BUG:

https://bugreports.qt-project.org/browse/QTBUG-5368

Bort

Answer 6

can be center like this too using layout if want to add more customization

// Create a widget that will contain a checkbox
 QWidget *checkBoxWidget = new QWidget();
 QCheckBox *checkBox = new QCheckBox();      // We declare and initialize the checkbox
 QHBoxLayout *layoutCheckBox = new QHBoxLayout(checkBoxWidget); // create a layer with reference to the widget
 layoutCheckBox->addWidget(checkBox);            // Set the checkbox in the layer
 layoutCheckBox->setAlignment(Qt::AlignCenter);  // Center the checkbox
 layoutCheckBox->setContentsMargins(0,0,0,0);    // Set the zero padding

ui->my_table_view->setCellWidget(row_number,column_number, checkBoxWidget);  // set cell widget

OR simply add left right margins

checkBox->setStyleSheet("margin-left:50%; margin-right:50%;");

Melodic

For some reason margin-left:50%; margin-right:50%; is giving me off-center with respect to the column heading. Any ideas. – Foliated

I ended up using the first method which worked correctly without the offset. – Foliated

Answer 7

#if QT_VERSION < 0x046000
#include <QCommonStyle>
class MyStyle : public QCommonStyle {
public:
  QRect subElementRect(SubElement subElement, const QStyleOption *option, const QWidget *widget = 0) const {
    switch(subElement) {
      case QStyle::SE_CheckBoxIndicator: {
        QRect r = QCommonStyle::subElementRect(subElement, option, widget);
        r.setRect( (widget->width() - r.width())/2, r.top(), r.width(), r.height());
        return QRect(r);
      }
      default: return QCommonStyle::subElementRect(subElement, option, widget);
    }
  }
};
#else
#include <QProxyStyle>
#include <QStyleFactory>
class MyStyle: public QProxyStyle {
public:
  MyStyle():QProxyStyle(QStyleFactory::create("Fusion")) {}
  QRect subElementRect(SubElement subElement, const QStyleOption *option, const QWidget *widget = 0) const {
    switch(subElement) {
      case QStyle::SE_CheckBoxIndicator: {
        QRect r = QProxyStyle::subElementRect(subElement, option, widget);
        r.setRect( (widget->width() - r.width())/2, r.top(), r.width(), r.height());
        return QRect(r);
      }
      default: return QProxyStyle::subElementRect(subElement, option, widget);
    }
  }
};
#endif

QCheckBox *box = new QCheckBox();
box->setStyle(new MyStyle());

Kief

Answer 8

For the regular rows of data, you can just adjust your model, testing the role in the data method. This seems to work for me:

if(role == Qt::TextAlignmentRole)
    {
    return(Qt::AlignHCenter); // or AlignCenter - either one works I beleive
    }

This does not get solved for the header however - so if you have a header with a checkbox (like select all), that won't be solved. But this solves the data problem of aligning at least.

Ariana