Qt: Multiple QListWidgets and only a single entry selected

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...