[SOLVED] Qt4 - QTableWidget selectedItems QProgressBar

Elfayer

Hello,
I have a QTableWidget with 6 columns. In the last column, the 6th (index 5, so), I have a QProgressBar.

I'm trying to change the value of the progress bar with :

@reinterpret_cast<QProgressBar*>(_table->selectedItems().at(5))->setValue(0);@

But it throw me an error :
"ASSERT failure in QList<T>::at: "index out of range", file c:\QtSDK\Desktop\Qt\4.8.1\msvc2010\include\QtCore/qlist.h, line 469"

Because in fact :

@std::cout << _table->selectedItems().length() << std::endl;@

returns me 5.

How is this possible ? I have a missing element here, that's why I have that error, but why ?

SGaist

Hi,

This a traditional counting vs programatic counting problem.

A size of 5 in standard counting means 1 to 5. But when you are programming, it means counting from 0 to 4.

Elfayer

Hi SGaist,
thanks for replying.

I have personally never seen a "counting" in programming from 0. When you do an strlen (C language), it counts from 1, not from 0. It begins from 0 when we use indexes.

But anyway, you're saying the lengh in correct, so why does

@reinterpret_cast<QProgressBar*>(_table->selectedItems().at(5))->setValue(0);@

throw me an error ?

Because this :

@_table->selectedItems().at(4)@

is giving me the good item, the one just before the progress bar.

I think it has something to do with the fact that I had to "setCellWidget" to add the progress bar to the table. But my table is parametered like follow :

@_table->setSelectionBehavior(QAbstractItemView::SelectRows);
_table->setSelectionMode(QAbstractItemView::SingleSelection);@

So it does select the progress the progress bar anyway. And I can see it selected.

SGaist

In a string the first char is at position 0

I agree with you about the fact that setting a widget on a cell might change the cell selection reaction. Whether this is the right behavior, I can't tell.

Check the size of_table->selectedItems(), It's probably 5.

You can always use the selected row number combined with the known column to retrieve the progress bar

Elfayer

I've found the problem. The problem is that I'm using "selectedItems" which returns me correctly the "items" ! But QProgressBar here is a QWidget. And my cast is wrong.

I'm casting a QTableWidgetItem* instead of a QWidget* to a QProgressBar*. So as you said, I have to use :

@reinterpret_cast<QProgressBar*>(_table->cellWidget(_table->selectedItems().at(0)->row(), 5))->setValue(0);@

to get the widget and not the item.

SGaist

Great you have it working !

But still, your error was about asking for an out of bound value, which has nothing to do with the faulty cast. So I am still wondering about the size of your selectItems()

Elfayer

I guess this is because the progress bar is not an item, but a Widget. And with selectedItems() I probably only get the items. That's why there were one element missing in the length().

SGaist

I also think so, but I wonder if this is the correct/intended behavior