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Thread: Must all cellWidgets in a QTable be the same widget type?

  1. #1
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    Default Must all cellWidgets in a QTable be the same widget type?

    I have a QTableWidget with QComboBoxs in row 0. External events will trigger changes to row zero--I was going to copy row 0 using the data associated with each comboboxes currentItem into a new row in the table.

    Right now, I get the QTable created with row 0 having the ComboBoxes. I can addItems for each combobox when the external event occurs with no issues.

    However, I wanted one of the columns to NOT have a QComboBox, but just a regular cell. But, when I don't do a setCellWidget on column 0, I get an exception when trying to add an item to the column 1 combobox.

    I tried using a QLabel for the cell widget for the column 0, row 0 cell and have the same problem.

    Is this expected? Maybe if one cell has a widget, all cells in the table must use the same widget?

    Here are the relevant code snippets.

    In constructor:

    Qt Code:
    1. // No widget desired in column 0
    2. runOrder->setItem(0,0, new QTableWidgetItem);
    3. //runOrder->setCellWidget(0,0,new QLabel);
    4.  
    5. // Comboboxes in columns 1 through seven of row 0
    6. for (int i=1;i<7;i++)
    7. {
    8. QComboBox *qb = new QComboBox;
    9. runOrder->setItem(0,i, new QTableWidgetItem);
    10. runOrder->setCellWidget(0,i, qb);
    11. connect(qb, SIGNAL(currentIndexChanged(int)), this,SLOT(check_lineup(int)));
    12.  
    13. }
    14.  
    15.  
    16. // Comboboxes in columns 1 through seven of row 0, not column 0
    17. for (int i=1;i<7;i++)
    18. {
    19. QComboBox *qb = new QComboBox;
    20. runOrder->setItem(0,i, new QTableWidgetItem);
    21. runOrder->setCellWidget(0,i, qb);
    22. connect(qb, SIGNAL(currentIndexChanged(int)), this,SLOT(check_lineup(int)));
    23.  
    24. }
    To copy to clipboard, switch view to plain text mode 
    In the code that adds entries to the comboboxes:
    Qt Code:
    1. //Loop through the columns of row zero that have comboBoxes
    2.  
    3. for (int i=1;i<5;i++)
    4. {
    5. QComboBox * qb = dynamic_cast<QComboBox *>(runOrder->cellWidget(0,i));
    6. qb->clear();
    7. //Loop through the lineup
    8. for (int j=0;j<5;j++)
    9. {
    10. QString dog_name= lineup_query.value(j).toString();
    11. qb->addItem(dog_name);
    12. }
    13. qb->setCurrentIndex(i);
    14.  
    15. }
    16.  
    17. If I change
    18.  
    19. // Comboboxes in columns 1 through seven of row 0
    20. for (int i=1;i<7;i++)
    21. {
    22. QComboBox *qb = new QComboBox;
    23. runOrder->setItem(0,i, new QTableWidgetItem);
    24. runOrder->setCellWidget(0,i, qb);
    25. connect(qb, SIGNAL(currentIndexChanged(int)), this,SLOT(check_lineup(int)));
    26.  
    27. }
    To copy to clipboard, switch view to plain text mode 
    to loop from 0 to 7, everything seems to work fine, except I get a comboBox in column zero I really don't want.

    Thanks,

    Dave Thomas
    Last edited by davethomaspilot; 9th January 2013 at 16:01. Reason: Code snippet for adding combobox items isn't the slot, but another method

  2. #2
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    Default Re: Must all cellWidgets in a QTable be the same widget type?

    Cell widgets can be of any type. I suggest you check the return value of dynamic_cast before trying to dereference the received pointer.
    Your biological and technological distinctiveness will be added to our own. Resistance is futile.

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  3. #3
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    Default Re: Must all cellWidgets in a QTable be the same widget type?

    The pointer returned from the dynamic_cast is not Null.

    Here's what it looks like:

    watch.jpg
    Also, note the line:


    qb->clear();

    Doesn't raise and excpetion

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    Default Re: Must all cellWidgets in a QTable be the same widget type?

    If it's not null then there is a combobox there. Where does the code crash? Show us the backtrace.
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  5. #5
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    Default Re: Must all cellWidgets in a QTable be the same widget type?

    It looks like the crash is occuring in a slot that got called as a result of an item change in the QComboBox. Here's my method for the slot:

    Qt Code:
    1. void CollectStats::check_lineup(int n)
    2. {
    3. QComboBox *changed_cell= dynamic_cast<QComboBox *>(sender());
    4. changed_cell->setStyleSheet("QComboBox { background-color: white;font:16pt }");
    5. for (int i=0;i<6;i++)
    6. {
    7.  
    8. QComboBox *qp = dynamic_cast<QComboBox *>(runOrder->cellWidget(0,i));
    9. if (sender() ==qp) continue;
    10. if (qp->currentIndex()==n)
    11. qp->setStyleSheet("QComboBox { background-color: red; font:16pt }");
    12. else
    13. qp->setStyleSheet("QComboBox { background-color: white; font:16pt }");
    14.  
    15. }
    16.  
    17. }
    To copy to clipboard, switch view to plain text mode 

    It looks like it's dying on the

    Qt Code:
    1. if (qp->currentIndex()==n)
    To copy to clipboard, switch view to plain text mode 

    I'm not sure how to print the stack trace from VS, so here are a couple of screen shots:
    stack2.pngstack1.jpg

    Thanks for the attention!

    Found it,

    Should be

    for (int i=1;i<7;i++)

    In the check_lineup method, after I eliminated the combobox in column 0.

    I feel stupid, thanks for your extremely fast replies--it got me pointed in the right direction!

    Dave Thomas

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