ui->addTab "index out of range" !?

Niagarer

Hey,
I have a normal mainwindow class, where I call in the constructor a function.
This function is supposed to add a new tab with a custom widget from another class to the tab widget.
Problem here: When I run this code, the program crashes at this line:

ui->tabGraph->addTab( myNewGraphWidget, "test");

with this error:

ASSERT failure in QVector<T>::operator[]: "index out of range"

I do not even use a vector here...
Any ideas?
Thanks for answers

mrjj

@Niagarer
Super. Found it

When you insert new tab. A signal is sent (currentChanged)

you catch signal ( its auto connected )
on_Graph_currentChanged(int index)
and then kill yourself with allNodesWidgets[index] as index is 100% surely out of bounds as nothing added to
allNodesWidgets yet.

void MainWindow::on_Graph_currentChanged(int index)
{
ui->allNodes_scrollArea->setWidget( allNodesWidgets[index] ); <<<< this gives the actual error
}

SGaist

Hi,

Can you provide a stack trace of your crash ?

Niagarer

@SGaist
uuuhhm..
I'm sorry, can you give me a link or sth. where I can see how...
Unfortunately don't really know what you mean... (do you men an exeption output? )

SGaist

What platform are you on ?

Niagarer

@SGaist
windows 10 x64

SGaist

MinGW or Visual Studio ?

Niagarer

@SGaist
MinGW 32bit

SGaist

Then you already have a debugger. Just start your application in debug mode, make it crash and you'll have the stack trace.

Niagarer

@SGaist
There is nothing under Stack when I am debugging...
Are my settings wrong? I can't find anything wrong.
Also nothing under Breakpoints, Threads, Modules, Source Files, Snapshots and Registers.
Only the Debugger Log shows content

SGaist

Silly question but are you starting the application as usual or are you starting it with the other button which means "debug the application" ?

Niagarer

@SGaist
No, I click Start Debugging
(but as I see now, there is Output in Modules tab when I am not closing the error message but it doesn't matter I think)

Niagarer

@SGaist
UPDATE
Ok now I know, there are two points in my function, where the program crashes.
My function:

    GraphWidget *newGraphWidget = new GraphWidget(this);
    graphWidgets.append(newGraphWidget);
    QString name = "tab " + QString::number(tabCounter);

    qDebug() << ui->Graph->currentIndex();

    //ui->Graph->addTab(newGraphWidget, "title");          // !? PROBLEM !?

    qDebug() << ui->Graph->currentIndex();


    tabCounter += 1;

    QVBoxLayout *vBoxLayout = new QVBoxLayout();
    vBoxLayout->setAlignment(Qt::AlignTop);
    QWidget *allNodesWidget = new QWidget();
    allNodesWidget->setLayout(vBoxLayout);
    //ui->allNodes_scrollArea->setWidget( allNodesWidgets[ui->Graph->currentIndex()] );     // !? PROBLEM !?
    allNodesWidgets.append(allNodesWidget);

The two lines where I commented !? PROBLEM !? are the two lines. If I uncomment one of these, the program crashes with the Index error. (UPDATE: the second one is because ui->Graph->currentIndex() is -1)
I have really no Idea what this means...
Help please!

Vinod Kuntoji

@Niagarer ,

What is the initial value of tabCounter? What is the vector size?

VRonin

This post is deleted!

VRonin

allNodesWidgets[ui->Graph->currentIndex()]

ui->Graph->currentIndex() is almost certainly out of bounds

Niagarer

@VRonin
Oh, yes you are right, thanks.
But it unfortunately does not solve teh actual problem :/

Niagarer

@Vinod-Kuntoji
The initial value of TabCounter is 0.
The vector has no specific size, it gets bigger when I add new items... what exactely do you mean?

Paul Busovikov

@Niagarer when you add new tab it do not mean that current index will be changed

Niagarer

@Paul-Busovikov
Yes...?
To get sure I wrote

    qDebug() << ui->Graph->currentIndex();

before and after adding a new tab

Niagarer

To make it easier:
the line

    ui->Graph->addTab(new QWidget(this), "hello");

does not work. Doesn't matter where I call it.