Working with PyQt and Qt designer ui files

Question

I'm new to PyQt and I'm trying to work with ui files directly from within my PyQt script. I have two ui files, mainwindow.ui and landing.ui. Clicking on a button 'pushButton' on the main window should open the landing window. However, clicking on the button does not work as I expected. Here is the code(I'm just trying to work stuff out so the code is pretty rough):

from PyQt4 import QtCore, uic
from PyQt4 import QtGui
import os

CURR = os.path.abspath(os.path.dirname('__file__'))

form_class = uic.loadUiType(os.path.join(CURR, "mainwindow.ui"))[0]
landing_class = uic.loadUiType(os.path.join(CURR, "landing.ui"))[0]

def loadUiWidget(uifilename, parent=None):
    uifile = QtCore.QFile(uifilename)
    uifile.open(QtCore.QFile.ReadOnly)
    ui = uic.loadUi(uifilename)
    uifile.close()
    return ui

@QtCore.pyqtSlot()
def clicked_slot():
    """this is called when login button is clicked"""
    LandingPage = loadUiWidget(os.path.join(CURR, "landing.ui"))
    center(LandingPage)
    icon(LandingPage)
    LandingPage.show()


class MyWindow(QtGui.QMainWindow, form_class):
    def __init__(self, parent=None):
        QtGui.QMainWindow.__init__(self, parent)
        self.setupUi(self)
        self.pushButton.clicked.connect(clicked_slot)

class LandingPage(QtGui.QMainWindow, landing_class):
    def __init__(self, parent=None):
        QtGui.QMainWindow.__init__(self, parent)
        self.setupUi(self)

def center(self):
    """ Function to center the application
    """
    qRect = self.frameGeometry()
    centerPoint = QtGui.QDesktopWidget().availableGeometry().center()
    qRect.moveCenter(centerPoint)
    self.move(qRect.topLeft())

def icon(self):
    """ Function to set window icon
    """
    appIcon = QtGui.QIcon("icon.png")
    self.setWindowIcon(appIcon)


if __name__ == "__main__":
    import sys
    app = QtGui.QApplication(sys.argv)
    pixmap = QtGui.QPixmap(os.path.join(CURR, "splash.png"))
    splash = QtGui.QSplashScreen(pixmap)
    splash.show()
    app.processEvents()    
    MainWindow = MyWindow(None)
    center(MainWindow)
    icon(MainWindow)
    MainWindow.show()
    splash.finish(MainWindow)
    sys.exit(app.exec_())

What mistake I'm I making??

Answer 1

There are two main problems with your script: firstly, you are not constructing the path to the ui files correctly; and secondly, you are not keeping a reference to the landing-page window (and so it will get garbage-collected immediately after it is shown).

Here is how the part of the script that loads the ui files should be structured:

import os
from PyQt4 import QtCore, QtGui, uic

# get the directory of this script
path = os.path.dirname(os.path.abspath(__file__))

MainWindowUI, MainWindowBase = uic.loadUiType(
    os.path.join(path, 'mainwindow.ui'))

LandingPageUI, LandingPageBase = uic.loadUiType(
    os.path.join(path, 'landing.ui'))

class MainWindow(MainWindowBase, MainWindowUI):
    def __init__(self, parent=None):
        MainWindowBase.__init__(self, parent)
        self.setupUi(self)
        self.pushButton.clicked.connect(self.handleButton)

    def handleButton(self):
        # keep a reference to the landing page
        self.landing = LandingPage()
        self.landing.show()

class LandingPage(LandingPageBase, LandingPageUI):
    def __init__(self, parent=None):
        LandingPageBase.__init__(self, parent)
        self.setupUi(self)