QStandardItemModel itemChanged signal not working



  • I created a QTableView which uses a QStandardItemModel populated with QStandardItem. I want it so that when I edit the values in one of the QStandardItem cells, a signal is emitted that will call the ItemChangeCallBack(QStandardItem&) function to change the color of the cell background.

    I have a TestGUI class that has the following member function which creates the data table. I tried debugging and it seems like the CallBack does not even get called.

    void TestGUI::CreateDataTables() {
    	QTableView* tableView = new QTableView(mainWindow);
    	QStandardItemModel* model = new QStandardItemModel(tableView);
    	for (uint8_t row = 0; row < 5; ++row) {
    		model->setItem(row, 0, new QStandardItem("test"));
    	}
    	tableView->setModel(model);
    	_mainLayout->addWidget(tableView);
    	QObject::connect(model, SIGNAL(itemChanged(QStandardItem&)), this, SLOT(ItemChangeCallback(QStandardItem&)));
    
     }
    

    Here is the ItemChangeCallback:

    void TestGUI::ItemChangeCallback(QStandardItem& item) {
    
    	item.setBackground(Qt::GlobalColor::red);
    
    }

  • Lifetime Qt Champion

    Hi,

    There's no signal with that signature. It's itemChanged(QStandardItem *)



  • @SGaist Hmm, I actually tried that as well and had the same problem.

    With the new code I have:

    void TestGUI::CreateDataTables() {
    	QTableView* tableView = new QTableView(mainWindow);
    	QStandardItemModel* model = new QStandardItemModel(tableView);
    	for (uint8_t row = 0; row < 5; ++row) {
    		model->setItem(row, 0, new QStandardItem("test"));
    	}
    	tableView->setModel(model);
    	_mainLayout->addWidget(tableView);
    	QObject::connect(model, SIGNAL(itemChanged(QStandardItem*)), this, SLOT(ItemChangeCallback(QStandardItem*)));
    
     }
    

    Here is the ItemChangeCallback:

    void TestGUI::ItemChangeCallback(QStandardItem* item) {
    
    	item->setBackground(Qt::GlobalColor::red);
    
    }

  • Lifetime Qt Champion

    Do you modify any item somewhere else than in ItemChangeCallback ? Otherwise it will never be called.



  • @SGaist Hmmm, don't think so, the item and model are only instantiated in the CreateDataTables() function so they can't be accessed without signals and slots. I think...

    Maybe I have to connect them in the constructor...?



  • @SGaist Hmm, although I do edit the model, I didn't give you all my code as I thought some of it would be irrelevant but here I also give the headers names:

    void TestGUI::CreateDataTables() {
    	QTableView* tableView = new QTableView(mainWindow);
    	QStandardItemModel* model = new QStandardItemModel(tableView);
    	QStringList headerList;
        for (uint8_t row = 0; row < 5; ++row) {
            model->setItem(row, 0, new QStandardItem("test"));
            headerList.append(QString("Some Header Names"));
            model->setVerticalHeaderLabels(headerList);
            model->setHorizontalHeaderLabels(QStringList("Values"));
    	}
    	tableView->setModel(model);
    	_mainLayout->addWidget(tableView);
    	QObject::connect(model, SIGNAL(itemChanged(QStandardItem*)), this, SLOT(ItemChangeCallback(QStandardItem*)));
    
     }

  • Lifetime Qt Champion

    You are editing the model before connecting the signal so you won't have anything emitted.



  • @justiliang said:

    QObject::connect(model

    Also I highly recommend always check result connect returns

    bool ok = QObject::connect(model .....
    Q_ASSERT( ok );

    This wil save you a lot of time


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