Qt: Multiple QListWidgets and only a single entry selected - qt

Question

I have several QListWidgets and would like to only allow a single row to be selected for all of these lists. So for example if I select a row in one of the lists any other selection in the other lists would be cleared. How can I achieve this?
Is there a built-in way to do this (similar to QButtonGroup for buttons)? If not, what approach would you recommend that I take when trying to implement this myself?
Grateful for help and with kind regards,
Tord

Answer 1

AFAIK, there is no ready built-in feature to provide a single selection in multiple list views.
Instead, it can be done by a respective signal handler for the QSelectionModel::selectionChanged signal which does this whenever the selection of one of the involved list views changes.
Thereby, you have to consider that clearing the selection will emit a selectionChanged signal as well. (Otherwise, you may end up in a recursive call of your signal handler until a stack overflow occurs.)
Unfortunately, I use Qt in C++. (My Python knowledge is rather limited.)
Thus, all I can provide for now is my "proof of concept" in C++:
#include <QtWidgets>
void singleSel(QListView *pLstView, const QList<QListView*> &pLstViews)
{
for (QListView *pLstViewI : pLstViews) {
if (pLstViewI == pLstView) continue; // skip sender
// the check is necessary to prevent recursions...
if (pLstView->selectionModel()->hasSelection()) {
// ...as this causes emission of selectionChanged() signal as well:
pLstViewI->selectionModel()->clearSelection();
}
}
}
int main(int argc, char **argv)
{
qDebug() << "Qt Version: " << QT_VERSION_STR;
QApplication app(argc, argv);
// build contents
QStandardItemModel tblModel(0, 1);
for (int i = 0; i < 10; ++i) {
tblModel.appendRow(
new QStandardItem(QString::fromUtf8("Entry %0").arg(i + 1)));
}
// build some GUI
QWidget win;
QHBoxLayout qHBox;
QListView lstView1;
lstView1.setModel(&tblModel);
qHBox.addWidget(&lstView1);
QListView lstView2;
lstView2.setModel(&tblModel);
qHBox.addWidget(&lstView2);
QListView lstView3;
lstView3.setModel(&tblModel);
qHBox.addWidget(&lstView3);
win.setLayout(&qHBox);
win.show();
// install signal handlers
QList<QListView*> pLstViews = { &lstView1, &lstView2, &lstView3 };
QObject::connect(lstView1.selectionModel(),
&QItemSelectionModel::selectionChanged,
[&lstView1, &pLstViews](const QItemSelection&, const QItemSelection &)
{
singleSel(&lstView1, pLstViews);
});
QObject::connect(lstView2.selectionModel(),
&QItemSelectionModel::selectionChanged,
[&lstView2, &pLstViews](const QItemSelection&, const QItemSelection &)
{
singleSel(&lstView2, pLstViews);
});
QObject::connect(lstView3.selectionModel(),
&QItemSelectionModel::selectionChanged,
[&lstView3, &pLstViews](const QItemSelection&, const QItemSelection &)
{
singleSel(&lstView3, pLstViews);
});
// exec. application
return app.exec();
}
I compiled and tested on Windows 10 (64 bit). This is how it looks:
Update:
I tried to port the C++ application to Python/PyQt5:
#!/usr/bin/python3
import sys
from PyQt5.QtWidgets import QApplication, QWidget, QHBoxLayout, QListView
from PyQt5.QtGui import QStandardItemModel, QStandardItem
def singleSelect(lstView, lstViews):
for lstViewI in lstViews:
if lstViewI == lstView:
continue
# the check is necessary to prevent recursions...
if lstViewI.selectionModel().hasSelection():
# ...as this causes emission of selectionChanged() signal as well:
lstViewI.selectionModel().clearSelection()
if __name__ == '__main__':
app = QApplication(sys.argv)
# build contents
tblModel = QStandardItemModel(0, 1)
for i in range(0, 10):
tblModel.appendRow(QStandardItem("Entry %d" % (i + 1)))
# build GUI
win = QWidget()
hBox = QHBoxLayout()
lstView1 = QListView()
lstView1.setSelectionMode(QListView.SingleSelection)
lstView1.setModel(tblModel)
hBox.addWidget(lstView1)
lstView2 = QListView()
lstView2.setSelectionMode(QListView.SingleSelection)
lstView2.setModel(tblModel)
hBox.addWidget(lstView2)
lstView3 = QListView()
lstView3.setSelectionMode(QListView.SingleSelection)
lstView3.setModel(tblModel)
hBox.addWidget(lstView3)
win.setLayout(hBox)
win.show()
# install signal handlers
lstViews = [lstView1, lstView2, lstView3]
lstView1.selectionModel().selectionChanged.connect(lambda sel, unsel: singleSelect(lstView1, lstViews))
lstView2.selectionModel().selectionChanged.connect(lambda sel, unsel: singleSelect(lstView2, lstViews))
lstView3.selectionModel().selectionChanged.connect(lambda sel, unsel: singleSelect(lstView3, lstViews))
# exec. application
sys.exit(app.exec_())
From what I saw in the test, it behaves similar like the one written in C++.
The only exception is that I have to click twice on an entry when I change the list view.
As I already said: my experiences in PyQt are very limited. (Actually, I started today by making this sample.) Thus, I may have overseen something. Please, take it with a grain of salt...