CODEWITHSUNDEEP
c++qtqtwidgets
dimas
dimas

Reputation: 13

QTWidgets QTableWidget crash with segfault

I have this signal on QPushButton:

void MainWindow::on_addNode_clicked()
{
    ui->nodesTable->insertRow(ui->nodesTable->rowCount());
    if(ui->nodesTable->rowCount()>1)
    {
        ui->nodesTable->item(ui->nodesTable->rowCount()-1, 0)->setText(ui->nodesTable->item(ui->nodesTable->rowCount()-2,0)->text());
    }
    else
    {
        ui->nodesTable->item(ui->nodesTable->rowCount()-1, 0)->setText(QString::fromStdString("0"));
    }
}

But it crashes with segmentation fault each time when I click the button. As I understood, item(...) give nullptr but why?

Upvotes: 1

Views: 1394

Answers (3)

thomas
thomas

Reputation: 330

You have to set the column count and you must set the item manually:

ui->nodesTable->setColumnCount(1);
ui->nodesTable->insertRow(ui->nodesTable->rowCount());
ui->nodesTable->setItem(ui->nodesTable->rowCount()-1, 0, new QTableWidgetItem("0") );
if(ui->nodesTable->rowCount()>1)
{
    ui->nodesTable->item(ui->nodesTable->rowCount()-1, 0)->setText(ui->nodesTable->item(ui->nodesTable->rowCount()-2,0)->text());
}
else
{
    ui->nodesTable->item(ui->nodesTable->rowCount()-1, 0)->setText(QString::fromStdString("0"));
}

Upvotes: 0

CMLDMR
CMLDMR

Reputation: 344

at the first time there is no item in your table, your application crashed if pointer pointed non and when you want to reach it!

try this;

void MainWindow::on_addNode_clicked()
{
    ui->nodesTable->insertRow(ui->nodesTable->rowCount());
    if( !ui->nodesTable->rowCount() )
    {
        ui->nodesTable->item(ui->nodesTable->rowCount()-1, 0)->setText(ui->nodesTable->item(ui->nodesTable->rowCount()-2,0)->text());
    }
    else
    {
        ui->nodesTable->setItem(0, 0,new QTableWidgetItem(QString("New Item")));
    }
}

Upvotes: 0

Darklighter
Darklighter

Reputation: 2192

Since you didn’t specify the number of rows and columns your QTableWidget starts with 0 rows and 0 columns, adding 1 row still leaves you with 0 columns.

Additionally you have to create your items first via setItem before you can access them via item

Please take a look at the overview in the docs.

On another note:
In the else branch of your if (ui->nodesTable->rowCount() > 1) rowCount() == 0 and therefore you access ui->nodesTable->item(-1, 0) which is out of bounds.

Upvotes: 2

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