PyQt5 QMessageBox with Details

QMessage.py

from PyQt5.QtWidgets import QApplication, QMainWindow, QLabel, QGridLayout, QWidget, QCheckBox, QSystemTrayIcon, \
    QSpacerItem, QSizePolicy, QMenu, QAction, QStyle, qApp, QMessageBox, QPushButton
from PyQt5.QtCore import QSize


class MainWindow(QMainWindow):
    """
         Сheckbox and system tray icons.
         Will initialize in the constructor.
    """
    check_box = None
    tray_icon = None

    # Override the class constructor
    def __init__(self):
        # Be sure to call the super class method
        QMainWindow.__init__(self)

        self.setMinimumSize(QSize(480, 80))  # Set sizes
        self.setWindowTitle("System Tray Application")  # Set a title
        central_widget = QWidget(self)  # Create a central widget
        self.setCentralWidget(central_widget)  # Set the central widget

        grid_layout = QGridLayout()  # Create a QGridLayout
        central_widget.setLayout(grid_layout)  # Set the layout into the central widget
        grid_layout.addWidget(QLabel("Application, which can minimize to Tray", self), 0, 0)

        # Add a checkbox, which will depend on the behavior of the program when the window is closed
        self.check_box = QCheckBox('Minimize to Tray')
        self.btn_check = QPushButton()
        self.btn_check.setText("show Message")
        grid_layout.addWidget(self.check_box, 1, 0)
        grid_layout.addWidget(self.btn_check, 2, 0)
        grid_layout.addItem(QSpacerItem(0, 0, QSizePolicy.Expanding, QSizePolicy.Expanding), 2, 0)

        # Init QSystemTrayIcon
        self.btn_check.clicked.connect(lambda: self.testmsg())
        self.tray_icon = QSystemTrayIcon(self)
        self.tray_icon.setIcon(self.style().standardIcon(QStyle.SP_ComputerIcon))

        '''
            Define and add steps to work with the system tray icon
            show - show window
            hide - hide window
            exit - exit from application
        '''
        show_action = QAction("Show", self)
        quit_action = QAction("Exit", self)
        hide_action = QAction("Hide", self)
        show_action.triggered.connect(self.show)
        hide_action.triggered.connect(self.hide)
        quit_action.triggered.connect(qApp.quit)
        tray_menu = QMenu()
        tray_menu.addAction(show_action)
        tray_menu.addAction(hide_action)
        tray_menu.addAction(quit_action)
        self.tray_icon.setContextMenu(tray_menu)
        self.tray_icon.show()

    # Override closeEvent, to intercept the window closing event
    # The window will be closed only if there is no check mark in the check box
    def closeEvent(self, event):
        if self.check_box.isChecked():
            event.ignore()
            self.hide()
            self.tray_icon.showMessage(
                "Tray Program",
                "Application was minimized to Tray",
                QSystemTrayIcon.Information,
                2000
            )

    def testmsg(self):
        msg = QMessageBox()
        msg.setIcon(QMessageBox.Information)
        msg.setWindowTitle("MyMessage")
        msg.setText("Hello world")
        msg.setInformativeText("this is more details")
        msg.setDetailedText("details text")
        msg.setStandardButtons(QMessageBox.Ok)
        msg.exec_()




if __name__ == "__main__":
    import sys

    app = QApplication(sys.argv)
    mw = MainWindow()
    mw.show()
    sys.exit(app.exec())

grid_layout = QGridLayout(self)

remove self

grid_layout = QGridLayout()

to prevent the error message

QLayout: Attempting to add QLayout "" to MainWindow "", which already has a layout

thanks do it