Slot for QListView::doubleClicked not getting called

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);
}