如何在主窗口的中心位置打开 QDialog 小部件

Question

Im looking for a way to open a QDialog widget on the center position of the main window. I have set the position of the mainwindow to center.

 centerPoint = qtw.QDesktopWidget().availableGeometry().center()
        qtRectangle.moveCenter(centerPoint)

to folow the dialog widget to the postion of the main window i have set it to

msgb.move(self.pos().x(), self.pos().y())

the dialog window follows the positon of the main window , but it opens on the top left side of the main window, how can I change its position to the center of the main window ?

#!/usr/bin/env python

"""
startscreen

base window remit to specific tests

"""

import os
import sys
from PyQt5 import QtWidgets as qtw
from PyQt5 import QtCore as qtc




class Startscreen(qtw.QWidget):
    '''
    remit to one of three tests if widgets toggled/clicked
    hide its self after
    '''

    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        # your code will go here

        # interface

        # position
        qtRectangle = self.frameGeometry()
        centerPoint = qtw.QDesktopWidget().availableGeometry().center()
        qtRectangle.moveCenter(centerPoint)
        self.move(qtRectangle.topLeft())
        # size
        self.resize(700, 410)
        # frame title
        self.setWindowTitle("Lambda")

        # heading
        heading_label = qtw.QLabel("Lambda Version 1.0")
        heading_label.setAlignment(qtc.Qt.AlignHCenter)

        # active user
        activeuser_label = qtw.QLabel('Benutzer: ' + os.getlogin())
        activeuser_label.setStyleSheet("background-color: rgb(234, 246, 22)")
        activeuser_label.setAlignment(qtc.Qt.AlignRight | qtc.Qt.AlignTop)

        # groubox for widget positioning
        self.groupbox = qtw.QGroupBox(self)
        # groupbox.setAlignment(qtc.Qt.AlignHCenter)

        # layout and widgets
        vlayout = qtw.QVBoxLayout()
        vlayout.setAlignment(qtc.Qt.AlignHCenter)

        self.particlesize_radiobutton = qtw.QRadioButton("test1")
        vlayout.addWidget(self.particlesize_radiobutton)
        self.dimensionalchange_radiobutton = qtw.QRadioButton("test2")
        vlayout.addWidget(self.dimensionalchange_radiobutton)
        self.dimensionalchangecook_radiobutton = qtw.QRadioButton("test3")
        vlayout.addWidget(self.dimensionalchangecook_radiobutton)
        self.select_button = qtw.QPushButton('select')
        vlayout.addWidget(self.select_button)

        self.groupbox.setLayout(vlayout)

        # mainlayout
        main_layout = qtw.QFormLayout()
        main_layout.addRow(activeuser_label)
        main_layout.addRow(heading_label)
        main_layout.setVerticalSpacing(40)
        main_layout.addRow(self.groupbox)

        self.setLayout(main_layout)

        # functionality
        self.select_button.clicked.connect(self.open_box)


        self.show()


    def open_box(self):
        msgb = qtw.QMessageBox()
        msgb.setWindowTitle("title")
        msgb.setText("hier sthet was")
        msgb.move(self.pos().x(), self.pos().y())
        run = msgb.exec_()

        # msgb = qtw.QMessageBox()
        # msgb.addButton()
        # if x open new windwo
        #



if __name__ == '__main__':
    app = qtw.QApplication(sys.argv)
    w = Startscreen()
    sys.exit(app.exec_())

Answer 1

A widget has a position relative to its parent, and if it does not have a parent then it will be relative to the screen. And in the case of msgb it belongs to the second case so you will have to convert the coordinate of the center of the window to global coordinates (that is to say with respect to the screen). Even doing the above it will not be centered because the position is with respect to the topleft, that is, the msgb topleft will be in the center of the screen which is not desirable so you have to also take into account the size of the msgb. And the size of the msgb before and after it is displayed is different so with a QTimer it will be enough:

def open_box(self):
    msgb = qtw.QMessageBox()
    msgb.setWindowTitle("title")
    msgb.setText("hier sthet was")
    
    run = msgb.exec_()