How to access widgets in centralWidget from stackedLayout?

Question

I have a QMainWindow in file Controller.py which creates a QmenuBar on the centralWidget and multiple files named as win0.py, win1.py, ... with different layouts nested in QstackedLayout. Now I want to enable/disable the buttons in the menubar in the Controller's mainWindow and get some variable / call functions in the centralWidget

This example is based on the following question which don't answer mine:

Using QStackedWidget for multi-windowed PyQt application

How to make nested StackedLayouts in PyQt5?

The closest question is:

Setting up stateChanged signal in QStackedWidget, pyqt

But none of them changes items on the MainWindow (Controller), like that what I try to do. See code for details.

controller.py:

import sys

from PyQt5.QtWidgets import *
from PyQt5 import QtCore

from win0 import W0     # sample window
#from win1 import W1     # further windows
#from win2 import W2

class Controller (QMainWindow):
    def __init__(self, parent=None):
        #super(Controller, self).__init__(parent)
        QMainWindow.__init__(self, parent)
        # used variables
        self.winDict = {}
        self.v1 = " self.V1 in Controller"

        # create stack
        self.stackLayout = QStackedLayout ()

        # put stack on MainWindow
        self.MainWidget =QWidget()
        self.MainWidget.setLayout(self.stackLayout)
        self.setCentralWidget(self.MainWidget)
        self.init_MenuBar ()

        # add further layouts
        self.init_Windows()
        # swith to first layout
        self.activeWin = self.switchWin (0)

    def init_MenuBar(self):

        self.toolbarButton_file = QPushButton (self.tr ("File"))
        self.toolbarButton_0 = QPushButton (self.tr ("Win0"))
        self.toolbarButton_1 = QPushButton (self.tr ("Win1"))
        self.toolbarButton_2 = QPushButton (self.tr ("Win2"))

        toolbar = self.addToolBar ("Window Manager")
        toolbar.addWidget (self.toolbarButton_file)
        toolbar.addWidget (self.toolbarButton_0)
        toolbar.addWidget (self.toolbarButton_1)
        toolbar.addWidget (self.toolbarButton_2)
        toolbar.setMovable (False)

        self.toolbarButton_0.clicked.connect ( (lambda: self.switchWin (0)))
        self.toolbarButton_1.clicked.connect ((lambda: self.switchWin (1)))
        self.toolbarButton_2.clicked.connect ((lambda: self.switchWin (2)))
        self.toolbarButton_0.setCheckable (False)
        self.toolbarButton_1.setCheckable(False)
        self.toolbarButton_2.setCheckable(False)
        self.toolbarButton_0.setEnabled (True)
        self.toolbarButton_1.setEnabled (True)
        self.toolbarButton_2.setEnabled (True)

    def init_Windows(self):
        self.switchWin(0, True)
        self.switchWin(1, True)
        self.switchWin(2, True)


    def switchWin(self, id=0, initonly = False):
        print ("-> switchWin:", id)
        if id not in self.winDict.keys ():
            if id == 0:
                self.winDict[id] = W0 ()
            #elif id == 1:
            #    self.winDict[id] = W1 ()
            #elif id == 2:
            #    self.winDict[id] = W2 ()
            self.stackLayout.addWidget (self.winDict[id])

        if not initonly:
            self.stackLayout.setCurrentIndex (id)
        Window = self.winDict[id]
        return Window

    def list_v1(self):
        print("-> Controller.list_V1")
        print("V1:", self.v1)

def main():
    App = QApplication(sys.argv)
    ProgramWindow = Controller()
    ProgramWindow.show()
    App.exec_()

if __name__ == "__main__":
    main()

win0.py (win1.py ... same fundament)

import sys
from PyQt5.QtWidgets import *
from PyQt5 import uic

class W0(QMainWindow):
    def __init__(self):
        super().__init__()
        self.ui = self.init_UI()
        self.v1 ="Variable in W0"
        self.ui.pushButton.clicked.connect (self.pbClicked)

    def init_UI(self):
        mainForm = ("win0.ui")
        print ("mainForm:", mainForm)
        Widget = uic.loadUi (mainForm, self)
        return Widget

    def pbClicked(self):
        print ("-> win0.pbClicked")
        self.parent().toolbarButton_0.setEnabled (False)       # There is the question
                                                               # How to access widgets and functions, variables on the
                                                               # centralWidget or MainWindow of Controller.py. I want to en/disable button in the menuBar e.g.

if __name__ == "__main__":
    App = QApplication (sys.argv)
    ProgramWindow = W0()
    ProgramWindow.show ()
    App.exec_ ()

win0.ui (same in win1.ui ...)

<?xml version="1.0" encoding="UTF-8"?>
<ui version="4.0">
 <class>MainWindow</class>
 <widget class="QMainWindow" name="MainWindow">
  <property name="geometry">
   <rect>
    <x>0</x>
    <y>0</y>
    <width>800</width>
    <height>600</height>
   </rect>
  </property>
  <property name="windowTitle">
   <string>MainWindow</string>
  </property>
  <widget class="QWidget" name="centralwidget">
   <widget class="QLabel" name="label">
    <property name="geometry">
     <rect>
      <x>10</x>
      <y>0</y>
      <width>43</width>
      <height>13</height>
     </rect>
    </property>
    <property name="text">
     <string>Win 0</string>
    </property>
   </widget>
   <widget class="QPushButton" name="pushButton">
    <property name="geometry">
     <rect>
      <x>60</x>
      <y>0</y>
      <width>80</width>
      <height>20</height>
     </rect>
    </property>
    <property name="text">
     <string>PushButton</string>
    </property>
   </widget>
   <widget class="QPushButton" name="pushButton_0">
    <property name="geometry">
     <rect>
      <x>180</x>
      <y>0</y>
      <width>80</width>
      <height>16</height>
     </rect>
    </property>
    <property name="text">
     <string>PushButton_0</string>
    </property>
   </widget>
  </widget>
  <widget class="QMenuBar" name="menubar">
   <property name="geometry">
    <rect>
     <x>0</x>
     <y>0</y>
     <width>800</width>
     <height>20</height>
    </rect>
   </property>
  </widget>
  <widget class="QStatusBar" name="statusbar"/>
 </widget>
 <resources/>
 <connections/>
</ui>

Using pyqt5 and python 3.7. I tried to use import from Controller which leads to endless loop and self.parent().toolbarButton_0.setEnabled (False) leads to
AttributeError: 'QWidget' object has no attribute 'toolbarButton_0'

Use slots and signals instead of trying to manipulate `Controller` from `W0` directly. — Heike, Aug 24 '19 at 12:58
Ok, can you give me an example, please. I tried already, but seems that I did it in a wrong way. — Papageno, Aug 24 '19 at 14:30

score 0 · Accepted Answer · answered Aug 24 '19 at 15:53

Instead of trying to manipulate the Controller widget from W0 directly, you could use signals and slots to communicate. For example, in W0 you could do something like

class W0(QMainWindow):
    button_clicked = QtCore.pyqtSignal()

    def __init__(self):
        ...
        self.ui.pushButton.clicked.connect(self.pbClicked)

    ....

    def pbClicked(self):
        print (f"-> win{self.id}.pbClicked")
        self.button_clicked.emit()

And in Controller

class Controller(QMainWindow):

    ....

    def switchWin(self, id=0, initonly = False):
        print ("-> switchWin:", id)
        if id not in self.winDict.keys ():
            if id == 0:
                self.winDict[id] = W0 ()
                self.winDict[id].button_clicked.connect(self.W0_button_clicked)
        ....

    def W0_button_clicked(self):
        self.toolbarButton_0.setEnabled (False)

Of course, in Controller.SwitchWin you could directly connect to the signal self.winDict[id].ui.pushButton.clicked, but creating a separate signal in W0 and emit that when the button is clicked has the advantage that you can change the Gui of W0 without having to rewrite the signal-slot connections in Controller. Also, you can use the signal to send additional data if needed by specifying input parameters for the signal.

How to access widgets in centralWidget from stackedLayout?

1 Answers1