QListWidget custom widget in item

main.py

"""Try to use a custom widget in a QListWidgetItem, expected result is test-row.ui widget in each row.

Actual result is blank lines.
Require PySide2, tested on Python 3.8.6
"""
import sys

from PySide2.QtWidgets import (
    QApplication,
    QHBoxLayout,
    QListWidget,
    QListWidgetItem,
    QMainWindow,
    QPushButton,
    QVBoxLayout,
    QWidget,
)
from PySide2.QtCore import QFile, Slot
from PySide2.QtUiTools import QUiLoader


def load_ui_widget(uifilename, parent=None):
    loader = QUiLoader()
    uifile = QFile(uifilename)
    uifile.open(QFile.ReadOnly)
    ui = loader.load(uifile, parent)
    uifile.close()
    return ui


class DeviceListWidgetItem(QWidget):
    def __init__(self, ui_file, *args, **kwargs):
        print("DeviceListWidgetItem inited ui_file: %r" % ui_file)
        super().__init__(*args, **kwargs)
        self.resize(400, 50)
        self.ui = load_ui_widget(ui_file, None)
        main_layout = QHBoxLayout()
        main_layout.addWidget(self.ui)
        self.setLayout(main_layout)

    def set_remove_callback(self, function):
        self.ui.remove_button.clicked.connect(lambda x=self: function(x))


class MyMainWindow(QMainWindow):
    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        self.add_button = QPushButton("add item")
        self.print_button = QPushButton("print item 0 label")
        self.list_widget = QListWidget()
        self.layout = QVBoxLayout()
        self.widget = QWidget()

        self.layout.addWidget(self.add_button)
        self.layout.addWidget(self.print_button)
        self.layout.addWidget(self.list_widget)
        self.widget.setLayout(self.layout)
        self.setCentralWidget(self.widget)

        self.add_button.clicked.connect(self.add_button_clicked)
        self.print_button.clicked.connect(self.print_button_clicked)

    @Slot(bool)
    def add_button_clicked(self, checked=False):
        print("add_buttonClicked checked:%r" % checked)
        widget = DeviceListWidgetItem(ui_file="test-row.ui")
        item = QListWidgetItem()
        self.list_widget.insertItem(self.list_widget.count(), item)
        self.list_widget.setItemWidget(item, widget)
        item.setSizeHint(widget.sizeHint())

    @Slot(bool)
    def print_button_clicked(self, checked=False):
        print("print_buttonClicked")
        print(self.list_widget.itemWidget(self.list_widget.item(0)).ui.label.text())


if __name__ == "__main__":
    app = QApplication(sys.argv)
    main_window = MyMainWindow()
    main_window.add_button_clicked()
    main_window.show()
    sys.exit(app.exec_())

test-row.ui

<?xml version="1.0" encoding="UTF-8"?>
<ui version="4.0">
 <class>Form</class>
 <widget class="QWidget" name="Form">
  <property name="geometry">
   <rect>
    <x>0</x>
    <y>0</y>
    <width>219</width>
    <height>32</height>
   </rect>
  </property>
  <property name="windowTitle">
   <string>Form</string>
  </property>
  <widget class="QWidget" name="layoutWidget">
   <property name="geometry">
    <rect>
     <x>0</x>
     <y>0</y>
     <width>208</width>
     <height>25</height>
    </rect>
   </property>
   <layout class="QHBoxLayout" name="horizontalLayout">
    <item>
     <widget class="QLabel" name="label">
      <property name="text">
       <string>Widgety widget</string>
      </property>
     </widget>
    </item>
    <item>
     <widget class="QPushButton" name="pushButton">
      <property name="text">
       <string>Widgety Button</string>
      </property>
     </widget>
    </item>
   </layout>
  </widget>
 </widget>
 <resources/>
 <connections/>
</ui>