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Suddenly getting crash when setting background color of QTableWidget



  • Hello, I am setting up a QTableWidget in the constructor of my main window as follows:
    @ ui->tableWidget->setRowCount(5);
    ui->tableWidget->setColumnCount(8);
    //QStringList *labels = new QStringList();
    QStringList labels;
    labels.append("Intake Pressure");
    labels.append("Intake Temperature");
    labels.append("Motor Temperature");
    labels.append("X Vibration");
    labels.append("Y Vibration");
    ui->tableWidget->setVerticalHeaderLabels(labels);@

    I get a crash below when I try to set the background color of some of the cells. This was working, then I was making changes unrelated to this widget, and it suddenly started crashing. I first noticed it crashing when I replaced the 0's in the second column with a variable. Then when I change them all back to 0, it still crashes.
    @//Set color of the cells to red
    QColor color( 240,0,0 );
    ui->tableWidget->item( 0, 0 )->setBackgroundColor( color ); //Crashing here
    ui->tableWidget->item( 1, 0 )->setBackgroundColor( color );
    ui->tableWidget->item( 2, 0 )->setBackgroundColor( color );
    ui->tableWidget->item( 3, 0 )->setBackgroundColor( color );
    ui->tableWidget->item( 4, 0 )->setBackgroundColor( color );@

    At the crash, the cursor is on the following line in qtablewidget.h:
    @ inline QColor backgroundColor() const
    { return qvariant_cast<QColor>(data(Qt::BackgroundColorRole)); }
    inline void setBackgroundColor(const QColor &color)
    { setData(Qt::BackgroundColorRole, color); } //Cursor is here@

    The crash window has a title bar "Signal received" and the content is "The inferior stopped because it received a signal from the Operating System. Signal name: SIGSEGV, Signal meaning: Segmentation fault" Any ideas what is going on?

    Thanks a lot,
    Ron


  • Lifetime Qt Champion

    Hi,

    You are not creating any item for your table widget so you are accessing a null pointer.

    You first need to populate your QTableWidget with QTableWidgetItems



  • You are right of course. What is different now is that no items get put in the table before I try to set the color. What I need to do is detect whether there are items there before I set the color.
    ...
    What I did was fill the table with '-' items as soon as the table is created.
    Thanks for the help.


  • Lifetime Qt Champion

    You can also set items with empty text if you don't want anything in the cells



  • Thanks, this helped!!!


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