QListWidget: problem with "itemWidget"

[Combas]

I try to reach a widget in a QListWidget, but the method "itemWidget" returns nothing, whereas the method "item" works correctly.
Extract of the code:

QWidget *currentWidget = nullptr;
    QListWidgetItem *currentItem = nullptr;
    QFont fontWidget;
    int numItem;

    numItem = listWidgetMain->currentRow();

    if ((numItem >= 0) && (numItem < listWidgetMain->count()))
    {
        currentItem = new QListWidgetItem();
        currentWidget = new QWidget();
        // The item is correctly selected
        currentItem = listWidgetMain->item(numItem);
        // The problem is here: the widget is not returned
        currentWidget = listWidgetMain->itemWidget(currentItem);
        fontWidget = currentWidget->font();
    }

The "currentItem" is ok, whereas the "currentWidget" is empty after the call to "itemWidget", and I don't understand why...
Could someone explain me:

• Why it does not work
• How to get the Widget address

The complete code is:

• mainwindow.h

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>
#include <QListWidget>
#include <QVBoxLayout>
#include <QPushButton>
#include <QWidget>

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    MainWindow(QWidget *parent = nullptr);
    ~MainWindow();

public slots:
    void Test();

private:
    QWidget *centralWidget;
    QListWidget *listWidgetMain;
    QVBoxLayout *vertLayoutMain;
    QPushButton *BT_test;
};
#endif // MAINWINDOW_H

• mainwindow.cpp:

#include "mainwindow.h"

MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
{
    int numLine;

    // QListWidget object
    listWidgetMain = new QListWidget();
    for (numLine = 0; numLine < 5; numLine++)
    {
        listWidgetMain->addItem("text_" + QString::number(numLine + 1));
    }

    // Test button
    BT_test = new QPushButton("Test");
    QObject::connect(BT_test, SIGNAL(clicked()), this, SLOT(Test()));

    // Layout with the list built
    vertLayoutMain = new QVBoxLayout();
    vertLayoutMain->addWidget(listWidgetMain);
    vertLayoutMain->addWidget(BT_test);

    // Main widget
    centralWidget = new QWidget();
    setCentralWidget(centralWidget);
    centralWidget->setLayout(vertLayoutMain);
}

MainWindow::~MainWindow()
{
}

void MainWindow::Test()
{
    QWidget *currentWidget = nullptr;
    QListWidgetItem *currentItem = nullptr;
    QFont fontWidget;
    int numItem;

    numItem = listWidgetMain->currentRow();

    if ((numItem >= 0) && (numItem < listWidgetMain->count()))
    {
        currentItem = new QListWidgetItem();
        currentWidget = new QWidget();
        // The item is correctly selected
        currentItem = listWidgetMain->item(numItem);
        // The problem is here: the widget is not returned
        currentWidget = listWidgetMain->itemWidget(currentItem);
        fontWidget = currentWidget->font();
    }
}

Thank you in advance for your help!
Laurent

[JonB]

@Combas said in QListWidget: problem with "itemWidget":

    // The problem is here: the widget is not returned
    currentWidget = listWidgetMain->itemWidget(currentItem);

What widget do you think should be returned? You obviously do not have any widget there, else it would be!

        currentItem = new QListWidgetItem();
        currentWidget = new QWidget();

I don't know what you are (intending to) doing here? You don't don't use these two newed items, so they are just a memory leak.

You must have something conceptually wrong. If you never put your widget into the list you'll never get it back from it. You have no setItemWidget() anywhere, so you're not.

P.S.
If you think

 listWidgetMain->addItem("text_" + QString::number(numLine + 1));

adds a widget it does not. It only adds an item. And unless you have some use case, you should not be using setItemWidget() or accessing itemWidget() anyway.

[Combas]

@JonB Thank you for your quick and clear answer.
Indeed, I thought that the "addItem" method added a widget... That was my mistake!

[JonB]

@Combas
Items are not widgets; they can be made to hold widgets (setItemWidget()), but don't do so unless you make them do so. If you can, try to stay away from putting any widgets of your own into tables/lists, they are "expensive". You don't need to unless it's some special case, normally just work with the items it naturally uses.