Segmentation fault while accessing textBox from callback

[column]

I have simple callback functions that provides data to be shown on QT widget main form. As soon breakpoint reaches setText() I have exception Segmentation fault:

void MainWindow::SetAmount(int value)
{
    ui->tbAmount->setText( QString::number(value) );

}

Why I'm geting souch error? When I call SetAmount() from button click it runs fine.

[mrjj]

Hi
Do you call it from another thread?

[JonB]

@column said in Segmentation fault while accessing textBox from callback:

As soon breakpoint reaches setText()

Do you mean when it hits breakpoint on that line before it executes the line, or do you mean as it executes that line?

But answer @mrjj first.

[Christian Ehrlicher]

@column said in Segmentation fault while accessing textBox from callback:

ui->tbAmount

I would guess the either ui or ui->tbAmount is not initialized.

[column]

@mrjj I suppose this callback that comes from .so library might be from other thread. Is that problem? How to solve it then?

[SGaist]

Hi,

Yes that is a problem, GUI elements should only be accessed/modified in the GUI thread. The cleanest way would be to use QMetaObject::invokeMethod using QueuedConnection so you ensure that the setText will be called in the correct context.

[column]

@JonB I mean "as it executes that line"