How to fix missing Task Bar icon in second QMainWindow widget - python-3.x

Question

I am making a GUI that had the Welcome page and the main page. The purpose is to let user agree on the welcome page, the welcome page is dismissed and the main page will show up for further step. However, the icon in the taskbar only shows up in the welcome page, when we click into the main window the icon is disappeared and the app appeared to be a minimized window on the bottom left corner in the screen.
The starting page and main window layout is appear like this.
class welcome_window(QtWidgets.QMainWindow):
def __init__(self,parent = None):
super(welcome_window, self).__init__(parent)
self.confirm_button = QtWidgets.QPushButton('Yes')
self.confirm_button.clicked.connect(self.startup)
Main_layout = QtWidgets.QHBoxLayout()
Main_layout.addWidget(self.confirm_button)
self.main.setLayout(Main_layout)
def startup(self):
self.close()
dialog = Main_window(self)
self.dialogs.append(dialog)
dialog.show()
class Main_window(QtWidgets.QMainWindow):
def __init__(self,parent = None):
super(Main_window, self).__init__(parent)
self.setGeometry(50, 50, 1500, 850)
# here is all the step for later operation
def main():
app = QtWidgets.QApplication(sys.argv)
main = welcome_window()
main.show()
sys.exit(app.exec_())
if __name__ == '__main__':
main()
I expected that if the icon located in the taskbar could always stay on, it would be great for my GUI. Thank you all.

Answer 1

First of all, the MRE you gave is not reproducible. When I tried to run it it just didn't work. In this case you had a simple issue so I could just guess what was intended, but when you get more complicated problems people might not be able to help you. So in the future please make sure that we can just copy-paste-execute your code.
The reason that the main window disappears is that it's a member of the Welcome window. When you close the Welcome window, the corresponding python object will deleted and therefore Python will no longer have a reference to the main window. The main window object will be garbage-collected and all kinds of strange things might happen (I would expect it to just disappear).
The solution is to have a reference to the main window that stays valid until the program closes. This can be done by defining it in the main function (and then giving it as a parameter to the Welcome window). Like this...
import sys
from PyQt5 import QtWidgets
# Use a QWidget if you don't need toolbars.
class welcome_window(QtWidgets.QWidget):
def __init__(self, main_window=None, parent = None):
super(welcome_window, self).__init__(parent)
self.main_window = main_window
self.confirm_button = QtWidgets.QPushButton('Yes')
self.confirm_button.clicked.connect(self.startup)
main_layout = QtWidgets.QHBoxLayout() # use lower case for variable names
main_layout.addWidget(self.confirm_button)
self.setLayout(main_layout)
def startup(self):
self.main_window.show()
self.close()
class Main_window(QtWidgets.QMainWindow):
def __init__(self,parent = None):
super(Main_window, self).__init__(parent)
self.setGeometry(50, 50, 1500, 850)
# here is all the step for later operation
# Don't use self.setLayout on a QMainWindow,
# use a central widget and set a layout on that.
self.main_widget = QtWidgets.QWidget()
self.setCentralWidget(self.main_widget)
main_layout = QtWidgets.QHBoxLayout()
self.main_widget.setLayout(main_layout)
main_layout.addWidget(QtWidgets.QLabel("Hello"))
def main():
app = QtWidgets.QApplication(sys.argv)
main = Main_window()
welcome = welcome_window(main_window=main)
welcome.show()
sys.exit(app.exec_())
if __name__ == '__main__':
main()
Some more tips. Don't use setLayout on a QMainWindow. Use a central widget and add your widgets to the layout of the central widget. The layout of the main window is for toolbars and such. See: https://doc.qt.io/qt-5/qmainwindow.html#qt-main-window-framework
Just use a QWidget if you want a simple window without toolbars (like your welcome window),
Best to use lower case for variable names and upper case for class names. E.g. I renamed Main_layout to main_layout. Look at the difference in syntax highlighting by Stack Overflow above.