Yes, everything works fine if I do not use setItemDelegate. I overrode createEditor, setEditor, setModelData, and updateModelGeometry. As I said before, my code works fine by itself, just not inside my db program.

Applying the delegate:
Qt Code: 
  1. if(viewInit)
  2. 	{
  3. 		model->submitAll();
  4. 		delete model;
  5. 	}
  6. 	int rowCount = 0;
  7. 	model = new QSqlTableModel();
  8. 	model->setTable(tableName);
  9. 	model->setEditStrategy(QSqlTableModel::OnManualSubmit);
  10. 	model->select();
  11. 	model->removeColumn(8);
  12. 	rowCount = model->rowCount();
  13. 	ui.tableTV->setModel(model);
  14. 	checkboxDelegate delegate;
  15. 	ui.tableTV->setItemDelegate(&delegate);
  16. 	ui.tableTV->resizeColumnToContents(2);
  17. 	ui.tableTV->hideColumn(0);
  18. 	ui.tableTV->setEditTriggers(QAbstractItemView::CurrentChanged);
  19. 	ui.tableTV->setAlternatingRowColors(true);
  20. 	ui.tableTV->scrollToBottom();
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The delegate:
Qt Code: 
  1. checkboxDelegate::checkboxDelegate(QObject *parent)
  2.     : QItemDelegate(parent)
  3. {
  4. }
  5.  
  6. QWidget *checkboxDelegate::createEditor(QWidget *parent,
  7.     const QStyleOptionViewItem &option,
  8.     const QModelIndex &index) const
  9. {
  10. 	if(index.isValid() && index.column() == checkboxCol)
  11. 	{
  12. 		QCheckBox *editor = new QCheckBox(parent);
  13.     	editor->installEventFilter(const_cast<checkboxDelegate*>(this));
  14.     	return editor;
  15.    	}
  16.    	else
  17.    	{
  18.    		return QItemDelegate::createEditor(parent, option, index);
  19.   		}
  20. }
  21.  
  22. void checkboxDelegate::setEditorData(QWidget *editor,
  23.                                     const QModelIndex &index) const
  24. {
  25. 	if(index.isValid() && index.column() == checkboxCol)
  26. 	{
  27. 		QString value = index.model()->data(index, Qt::DisplayRole).toString();
  28.  
  29.     	QCheckBox *checkBox = static_cast<QCheckBox*>(editor);
  30.     	if(value == "Y")
  31.     		checkBox->setCheckState(Qt::Checked);
  32.     	else
  33.     		checkBox->setCheckState(Qt::Unchecked);
  34.    		}
  35.    		else
  36.    		{
  37.    			QItemDelegate::setEditorData(editor, index);
  38.   			}
  39. }
  40.  
  41. void checkboxDelegate::setModelData(QWidget *editor, QAbstractItemModel *model,
  42.                                    const QModelIndex &index) const
  43. {
  44. 	if(index.isValid() && index.column() == checkboxCol)
  45. 	{
  46.     	QCheckBox *checkBox = static_cast<QCheckBox*>(editor);
  47.     	QString value;
  48.    		if(checkBox->checkState() == Qt::Checked)
  49.    			value = "Y";
  50.    		else
  51.    			value = "N";
  52.  
  53.     	model->setData(index, value);
  54.    	}
  55.    	else
  56.    	{
  57.    		QItemDelegate::setModelData(editor, model, index);
  58.   		}
  59. }
  60.  
  61. void checkboxDelegate::updateEditorGeometry(QWidget *editor,
  62.     const QStyleOptionViewItem &option, const QModelIndex &index) const
  63. {
  64. 	if(index.isValid() && index.column() == checkboxCol)
  65. 	    editor->setGeometry(option.rect);
  66. 	else
  67. 		QItemDelegate::updateEditorGeometry(editor, option, index);
  68.  
  69. }
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