QListView/QListWidget with custom items and custom item widgets

I'm writing a PyQt application and am having some trouble creating a custom list view. I'd like the list to contain arbitrary widgets (one custom widget in particular). How would I go about this?

It seems that the alternative would be to create a table or grid view wrapped in a scrollbar. However, I'd like to be able to take advantage of the model/view approach as well as the nesting (tree-view) support the built-ins handle.

To clarify, the custom widgets are interactive (contain buttons), so the solution requires more than painting a widget.

I think you need to subclass QItemDelegate.

QItemDelegate can be used to provide custom display features and editor widgets for item views based on QAbstractItemView subclasses. Using a delegate for this purpose allows the display and editing mechanisms to be customized and developed independently from the model and view.

This code is taken from Qt's examples, the torrent application.

class TorrentViewDelegate : public QItemDelegate
{
    Q_OBJECT
public:
    inline TorrentViewDelegate(MainWindow *mainWindow) : QItemDelegate(mainWindow) {}

    inline void paint(QPainter *painter, const QStyleOptionViewItem &option,
                      const QModelIndex &index ) const
    {
        if (index.column() != 2) {
            QItemDelegate::paint(painter, option, index);
            return;
        }

        // Set up a QStyleOptionProgressBar to precisely mimic the
        // environment of a progress bar.
        QStyleOptionProgressBar progressBarOption;
        progressBarOption.state = QStyle::State_Enabled;
        progressBarOption.direction = QApplication::layoutDirection();
        progressBarOption.rect = option.rect;
        progressBarOption.fontMetrics = QApplication::fontMetrics();
        progressBarOption.minimum = 0;
        progressBarOption.maximum = 100;
        progressBarOption.textAlignment = Qt::AlignCenter;
        progressBarOption.textVisible = true;

        // Set the progress and text values of the style option.
        int progress = qobject_cast<MainWindow *>(parent())->clientForRow(index.row())->progress();
        progressBarOption.progress = progress < 0 ? 0 : progress;
        progressBarOption.text = QString().sprintf("%d%%", progressBarOption.progress);

        // Draw the progress bar onto the view.
        QApplication::style()->drawControl(QStyle::CE_ProgressBar, &progressBarOption, painter);
    }
};

Basically as you can see it checks if the column to be painted is of a specific index, if so it paints a progress bar. I think you could tweak it a little and instead of using a QStyleOption you could use your own widget.

edit: don't forget to setup your item delegate with your QListView using setItemDelegate.

While investigating your question I've stumbled upon this thread, which elaborates how to paint a custom widget using a QItemDelegate, I believe it has all the info you might need.

If I understand your question correctly, you want something like this:

where each row contains a custom set of widgets.

To achieve this, two steps.

Implement the row with a custom Widget

First, implement a custom widget that contains all the widgets needed per list row.

Here I am using a label and two buttons per row, with an horizontal layout.

class MyCustomWidget(QWidget):
    def __init__(self, name, parent=None):
        super(MyCustomWidget, self).__init__(parent)

        self.row = QHBoxLayout()

        self.row.addWidget(QLabel(name))
        self.row.addWidget(QPushButton("view"))
        self.row.addWidget(QPushButton("select"))

        self.setLayout(self.row)

Add rows to the list

Instanciating multiple rows is then just a matter of creating a widget item, and associate the custom widget to the item's row.

# Create the list
mylist = QListWidget()

# Add to list a new item (item is simply an entry in your list)
item = QListWidgetItem(mylist)
mylist.addItem(item)

# Instanciate a custom widget 
row = MyCustomWidget()
item.setSizeHint(row.minimumSizeHint())

# Associate the custom widget to the list entry
mylist.setItemWidget(item, row)

@Idan's answer works well, but I'll post a simpler example I came up with. This item delegate just draws a black rectangle for each item.

class ItemDelegate : public QItemDelegate
{
public:
    explicit ItemDelegate(QObject *parent = 0) : QItemDelegate(parent) {}
    void paint(QPainter *painter, const QStyleOptionViewItem &option, const QModelIndex &index) const
    {
        painter->fillRect(option.rect.adjusted(1, 1, -1, -1), Qt::SolidPattern);
    }
};

And then you just need to set it for the list widget:

ui->listWidget->setItemDelegate(new ItemDelegate(ui->listWidget));