QStandardItemModel itemChanged signal not working

justiliang

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);

}

SGaist

Hi,

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

justiliang

@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);

}

SGaist

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

justiliang

@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...?

justiliang

@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*)));

 }

SGaist

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

alex_malyu

@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