QTableWidget cell widget "parent" questions

bigguiness

Hello all,

I have a QTableWidget that has a number of columns that need number only input and others that have text input.

Right now I just allocate a QTableWidgetItem for each cell, set the QT::ItemIsEditable flag (among others), and then do a setItem() for the cell. Basically:

for (int row = 0; row < NUM_ROWS; row++) {
    for (int col = 0; col < NUM_COLS; col++) {
        QTableWidgetItem* const i = new QTableWidgetItem;
        i->setFlags(Qt::ItemIsEnabled | Qt::ItemIsEditable);
        table->setItem(row, col, i);
    }
}

I then just do this to get the cell text:

QString s = table->item(row, col)->text();

Some of the cells need the input data to be numbers. I figured out I can allocate a QLineEdit for those cells and then set a validator:

for (int row = 0; row < NUM_ROWS; row++) {
    for (int col = 0; col < NUM_COLS; col++) {
        QTableWidgetItem* const i = new QTableWidgetItem;
        if (col == 0) {
            QLineEdit* edit = new QLineEdit;        // should this have a parent? what is it?
            edit->setFrame(false);
            edit->setValidator(new QIntValidator);  // should this have a parent? what is it?
            t->setCellWidget(row, col, edit);
        } else {
            i->setFlags(Qt::ItemIsEnabled | Qt::ItemIsEditable);
        }
        table->setItem(row, col, i);
    }
}

I'm just not sure if the QLineEdit and QIntValidator should have a parent and if so what that parent should be.

Also, do the cells that contain a QLineEdit widget need the QTableWidgetItem allocated and set in the table?

Thanks

SGaist

Hi,

Rather than add widgets to every cell, you should implement a custom QStyledItemDelegate that will provide the adequate editor.

JonB

@bigguiness
setCellWidget() will mean the table takes ownership of the QLineEdit, and setValidator() means the line edit owns the QIntValidator. So your parentage calls don't matter.

You might prefer to use a dedicated QSpinBox over a QLineEdit with a validator, have a look at it.

Having said this, setCellWidget() is "frowned upon", because you can use too many resources if you have many items in your table. @SGaist's recommendation is the better way to do this.

bigguiness

Thanks for the information about the ownership.

I'm still learning how Qt works. The custom QStyledItemDelegate is probably the best way to go but I really don't understand it and how the model/view stuff work.

Most of the comments I see just say "read the docs". Unfortunately that only helps if you have some idea of how it works already...

I'll keep trying to get it to work the way I am doing it for right now.

mchinand

If you haven't read it yet, I suggest you read the model view tutorial which helped me understand how the various classes work together much better than by just reading the individual class documentation pages.