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[SOLVED] Qt4 - QTableWidget selectedItems QProgressBar

  • 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 :


    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 ?

  • Lifetime Qt Champion


    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.

  • 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


    throw me an error ?

    Because this :


    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 :


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

  • Lifetime Qt Champion

    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

  • 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.

  • Lifetime Qt Champion

    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()

  • 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().

  • Lifetime Qt Champion

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

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