Connect QListWidgetItem in setupUI [duplicate] - python-3.x

Question

This question already has answers here:
Why does pyqtSlot decorator cause "TypeError: connect() failed"?
(2 answers)
Closed 3 years ago.
I want to drag &drop a file to a listwidget and when itemactivated, plaintextedit opens and readAll lines in file. But returned with error: "connect() failed between itemActivated(QListWidgetItem*) and read_txt()"
from PyQt5 import QtCore, QtGui, QtWidgets
import sys
class Ui_MainWindow(object):
def setupUi(self, MainWindow):
MainWindow.setObjectName("MainWindow")
MainWindow.resize(873, 663)
self.centralwidget = QtWidgets.QWidget(MainWindow)
self.centralwidget.setObjectName("centralwidget")
MainWindow.setCentralWidget(self.centralwidget)
self.listWidget = listWidget(self.centralwidget)
self.listWidget.setGeometry(QtCore.QRect(150, 330, 256, 192))
self.listWidget.setObjectName("listWidget")
self.plainTextEdit = QtWidgets.QPlainTextEdit(self.centralwidget)
self.plainTextEdit.setGeometry(QtCore.QRect(440, 200, 104, 87))
self.plainTextEdit.setObjectName("plainTextEdit")
self.listWidget.itemActivated.connect(self.read_txt)
QtCore.QMetaObject.connectSlotsByName(MainWindow)
#QtCore.pyqtSlot("QListWidgetItem*")
def read_txt(self,links):
file = QtCore.QFile(links.text())
if file.open(QtCore.QFile.ReadOnly | QtCore.QFile.Text):
self.plainTextEdit.setPlainText(file.readAll().data().decode())
class listWidget(QtWidgets.QListWidget):
def __init__(self, parent):
super().__init__(parent)
self.setAcceptDrops(True)
def dragEnterEvent(self, event):
if event.mimeData().hasUrls:
event.acceptProposedAction()
else:
event.ignore()
def dragMoveEvent(self, event):
if event.mimeData().hasUrls:
event.setDropAction(QtCore.Qt.CopyAction)
event.acceptProposedAction()
else:
event.ignore()
def dropEvent(self, event):
if event.mimeData().hasUrls:
event.setDropAction(QtCore.Qt.CopyAction)
for url in event.mimeData().urls():
links=QtWidgets.QListWidgetItem(url.toLocalFile())
self.addItem(links)
event.acceptProposedAction()
if __name__ == "__main__":
if not QtWidgets.QApplication.instance():
app = QtWidgets.QApplication(sys.argv)
else:
app = QtWidgets.QApplication.instance()
MainWindow = QtWidgets.QMainWindow()
ui = Ui_MainWindow()
ui.setupUi(MainWindow)
MainWindow.show()
app.exec_()
Drag and drop works fine but could not connect QListWidgetItem with readtxt method in setupUi. What is the problem ??

Answer 1

The problem is that the #pyqtSlot decorator can only be used in a class that inherits from QObject. You can connect signals to any callable object so the easiest way is to just omit the decorator, but if you do need it for one reason or another, you could subclass QMainWindow and define the slot in there, e.g.
class MyMainWindow(QtWidgets.QMainWindow):
def __init__(self, *args, **kwargs):
super().__init__(*args, **kwargs)
self.ui = Ui_MainWindow()
self.ui.setupUi(self)
self.ui.listWidget.itemActivated.connect(self.read_txt)
#QtCore.pyqtSlot("QListWidgetItem*")
def read_txt(self, links):
file = QtCore.QFile(links.text())
if file.open(QtCore.QFile.ReadOnly | QtCore.QFile.Text):
self.ui.plainTextEdit.setPlainText(file.readAll().data().decode())
if __name__ == '__main__':
...
mainWindow = MyMainWindow()
mainWindow.show()
...