Slot for QListView::doubleClicked not getting called - c++

Question

I have a QListView named listView. It is the only widget in the MainWindow. I want to track the double clicks on the listView. So, I did this:
#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <QMessageBox>
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
listView = new QListView(this);
this->setCentralWidget(listView);
connect(listView, &QListView::doubleClicked, this, &MainWindow::onDoubleClicked);
}
MainWindow::~MainWindow()
{
delete ui;
}
void MainWindow :: onDoubleClicked(const QModelIndex &index)
{
QMessageBox :: information(this, "Info", "List view was double clicked at\nColumn: " + QString :: number(index.column()) + " and Row: " + QString::number(index.row()));
}
But when I double click the listView a get no message box

Answer 1

If the docs are reviewed:
void QAbstractItemView::doubleClicked(const QModelIndex &index)
This signal is emitted when a mouse button is double-clicked. The item
the mouse was double-clicked on is specified by index. The signal is
only emitted when the index is valid.
In your case, your QListView does not have a model, so when you click there is no valid QModelIndex, so the signal will not be emitted.
If you want to follow the double-click event there are 2 possible solutions:
Create a QListView and overwrite the mouseDoubleClickEvent event.
Or use an event filter.
In my solution I will use the second method:
*.h
#ifndef MAINWINDOW_H
#define MAINWINDOW_H
#include <QMainWindow>
class QListView;
namespace Ui {
class MainWindow;
}
class MainWindow : public QMainWindow
{
Q_OBJECT
public:
explicit MainWindow(QWidget *parent = 0);
~MainWindow();
bool eventFilter(QObject *watched, QEvent *event);
private:
Ui::MainWindow *ui;
QListView *listView;
};
#endif // MAINWINDOW_H
*.cpp
#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <QEvent>
#include <QListView>
#include <QMouseEvent>
#include <QDebug>
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
listView = new QListView;
this->setCentralWidget(listView);
listView->viewport()->installEventFilter(this);
}
MainWindow::~MainWindow()
{
delete ui;
}
bool MainWindow::eventFilter(QObject *watched, QEvent *event)
{
if(watched == listView->viewport() && event->type() == QEvent::MouseButtonDblClick){
QMouseEvent *mouseEvent = static_cast<QMouseEvent*>(event);
qDebug()<<"MouseButtonDblClick"<<mouseEvent->pos();
}
return QMainWindow::eventFilter(watched, event);
}