KeypressEvent not working, How to correct it? - pyqt4

Question

I am trying to get keypressevent work with the following code
import sys,
from PyQt4 import QtCore, QtGui
class Ui_MainWindow(QtGui.QWidget):
def __init__(self):
super(Ui_MainWindow, self).__init__()
def keyPressEvent(self, event):
print 'a'
def setupUi(self, MainWindow):
MainWindow.setObjectName(("MainWindow"))
MainWindow.resize(371, 345)
MainWindow.setMaximumSize(QtCore.QSize(401, 600))
MainWindow.setWindowIcon(QtGui.QIcon('icons/icon.png'))
screen = QtGui.QDesktopWidget().screenGeometry()
mysize = MainWindow.geometry()
hpos = ( screen.width() - mysize.width() ) / 2
vpos = ( screen.height() - mysize.height() ) / 2
MainWindow.move(hpos, vpos)
#some GUI
MainWindow.setCentralWidget(self.centralwidget)
cd=MainWindow.centralWidget()
cd.setFocusPolicy(QtCore.Qt.StrongFocus)
cd.setFocus()
self.actionHardware = QtGui.QAction(MainWindow)
self.actionHardware.setObjectName(("actionHardware"))
self.retranslateUi(MainWindow)
#COnnect odes
def retranslateUi(self, MainWindow):
#sime button text codes
if __name__=="__main__" :
app = QtGui.QApplication(sys.argv)
MainWindow = QtGui.QMainWindow()
ui = Ui_MainWindow()
ui.setupUi(MainWindow)
MainWindow.show()
sys.exit(app.exec_())
The code was partially generated using QTDesigner. I noticed that replacing Mainwindow.show() by ui.show() enables keypressevent but at the cost of not showing any buttons i create in the Mainwindow central widget

Answer 1

It looks like the problem is in the way you are re-using the code output by Designer. You defined Ui_MainWindow.keyPressEvent, and created an instance "ui" of the class. However: "ui" is never directly incorporated into the GUI anywhere (ui.setupUi adds other widgets, but not itself, to MainWindow) and thus events are never delivered to ui.
My approach would look more like this:
class Ui_MainWindow(object): ## note this does not need to inherit QWidget
... ## and ideally, this code should not be changed
... ## after designer generates it
...
class Window(QtGui.QMainWindow):
def __init__(self):
super(Window, self).__init__()
self.ui = Ui_MainWindow()
self.ui.setupUi(self)
def keyPressEvent(self, ev):
print "key press"
if __name__ == "__main__":
app = QtGui.QApplication(sys.argv)
MainWindow = Window()
MainWindow.show()
sys.exit(app.exec_())