keyPressEvent is not working in my PyQt application - python-3.x

Question

I am trying to use keyPressEvent in a mainwindow I generated with QtDesigner but no key press is detected by my program. Here is my code
The QtDesigner generated class is MainWindowUI.
class MainWindow(QMainWindow,MainWindowUI.Ui_MainWindow):
def __init__(self, translator,parent=None):
QMainWindow.__init__(self, parent=parent)
#super(MainWindow,self).__init__(parent)
self.setupUi(self)
self.translator=translator
self.completeGUI()
def completeGUI(self):
self.setConnections()
self.set_line_edit_validators()
self.category_combo.insertSeparator(4)
self.category_combo.insertSeparator(8)
self.type_conjug_combo.insertSeparator(3)
self.type_conjug_combo.insertSeparator(6)
#self.type_conjug_combo.setItemData( 0, QtGui.QColor('red'), QtCore.Qt.ForegroundRole )
self.save_button.clicked.connect(self.fileSave)
self.category_label.hide()
self.category_combo.hide()
self.type_conjug_label.hide()
self.type_conjug_combo.hide()
self.grammar_combo.setStyleSheet("color:red")
self.category_combo.setStyleSheet("color:red;")
self.type_conjug_combo.setStyleSheet("color:red;")
self.palat_combo.setStyleSheet("color:red;")
self.accent_combo.setStyleSheet("color:red;")
self.terme_edit.setStyleSheet("border: 2px solid red;")
print("completeGUI is over")
def keyPressEvent(self, e):
print(e.key())
I had a look at various answers to analog question on this forum but I could not manage to have it working.
Thank you for help.
HERE IS A MINIMAL EXAMPLE THAT REPRODUCES THE TROUBLE
from PyQt5 import QtCore
from PyQt5.QtWidgets import QApplication
import sys
from view.NewMainWindow import NewMainWindow
if __name__=='__main__':
app = QApplication(sys.argv)
translator = QtCore.QTranslator()
app.installTranslator(translator)
mainWindow = NewMainWindow(translator)
NewMainWindow.show(mainWindow)
#sys.exit(app.exec_())
current_exit_code=app.exec_()
app=None
AND THE NEWMAINWINDOW
from PyQt5.QtWidgets import QMainWindow
from gen import NewMainWindowUI
class NewMainWindow(QMainWindow,NewMainWindowUI.Ui_MainWindow):
def __init__(self,translator, parent=None):
super(NewMainWindow,self).__init__(parent)
self.setupUi(self)
print('init completed')
def keyPressEvent(self, e):
print('event detected')
print(e.key())
THE GENERATED INTERFACE
# -*- coding: utf-8 -*-
# Form implementation generated from reading ui file 'src/designer/newmainwindow.ui'
#
# Created by: PyQt5 UI code generator 5.13.1
#
# WARNING! All changes made in this file will be lost!
from PyQt5 import QtCore, QtGui, QtWidgets
class Ui_MainWindow(object):
def setupUi(self, MainWindow):
MainWindow.setObjectName("MainWindow")
MainWindow.resize(800, 600)
self.centralwidget = QtWidgets.QWidget(MainWindow)
self.centralwidget.setObjectName("centralwidget")
self.lineEdit = QtWidgets.QLineEdit(self.centralwidget)
self.lineEdit.setGeometry(QtCore.QRect(130, 110, 113, 36))
self.lineEdit.setObjectName("lineEdit")
MainWindow.setCentralWidget(self.centralwidget)
self.menubar = QtWidgets.QMenuBar(MainWindow)
self.menubar.setGeometry(QtCore.QRect(0, 0, 800, 29))
self.menubar.setObjectName("menubar")
MainWindow.setMenuBar(self.menubar)
self.statusbar = QtWidgets.QStatusBar(MainWindow)
self.statusbar.setObjectName("statusbar")
MainWindow.setStatusBar(self.statusbar)
self.retranslateUi(MainWindow)
QtCore.QMetaObject.connectSlotsByName(MainWindow)
def retranslateUi(self, MainWindow):
_translate = QtCore.QCoreApplication.translate
MainWindow.setWindowTitle(_translate("MainWindow", "MainWindow"))
if __name__ == "__main__":
import sys
app = QtWidgets.QApplication(sys.argv)
MainWindow = QtWidgets.QMainWindow()
ui = Ui_MainWindow()
ui.setupUi(MainWindow)
MainWindow.show()
sys.exit(app.exec_())

Answer 1

I usually avoid calling a keyPressEvent from both the central widget and the main window, because, as #musicamante said, one could be "consuming" the other. Especially if you plan on switching between multiple central widgets.
You should instead create a slot on a QMainWindow object connected to the central widget's keyPressEvent (but name it something else, like onKeyPressEvent or something) and then you emit the event from inside the MainWindow's keyPressEvent, something like this:
from PyQt5.QtWidgets import QApplication, QMainWindow, QWidget
from PyQt5.QtCore import pyqtSignal, pyqtSlot
from PyQt5.QtGui import QKeyEvent
class MainWindow(QMainWindow):
key_pressed = pyqtSignal(QKeyEvent)
def __init__(self, *args, **kwargs) -> None:
super().__init__(*args, **kwargs)
central_widget = NewWindow()
self.key_pressed.connect(central_widget.onKeyPressEvent)
self.setCentralWidget(central_widget)
...
def keyPressEvent(self, event: QKeyEvent) -> None:
self.key_pressed.emit(event)
return super().keyPressEvent(event)
class NewWindow(QWidget):
def __init__(self, *args, **kwargs) -> None:
super().__init__(*args, **kwargs)
...
#pyqtSlot(QKeyEvent)
def onKeyPressEvent(self, event: QKeyEvent) -> None:
print(event.key())
return