@charry
Yes, you are normally supposed to double-click to edit a cell (one click to select the cell, double-click to edit the cell).

If you want single-click to edit, you should look at, say, QTableView::setEditTriggers(QAbstractItemView::AllEditTriggers). See if one of those values do what you want? If not, have a read through e.g. https://stackoverflow.com/questions/18831242/qt-start-editing-of-cell-after-one-click, there are other possibilities there. Or further hits via Google qtableview click edit.