How to resize subwindows window in mdiArea?

Question

Python

When I add a window to mdiArea, it becomes small. How to make the window when opened becomes the size that is set in the designer?
Screenshot of the designer Screenshot

of the program
i.stack.imgur.com/s2gi7.jpg
code

main_class, main_base_class = loadUiType(getcwd() + '/ui/main.ui')
class MainWindow(QMainWindow, main_class):
    def __init__(self, *args):
       self.user = my_class.User
       super(MainWindow, self).__init__(*args)
       self.setupUi(self)
       self.show()
       self.setDisabled(True)
       self.login = login_window.LoginWindow(self, self.user)
       self.login.show()

    def set_privilege(self):
       if self.user.privilege == "швея":
           self.ma_material.setDisabled(True)
           self.ma_material_provider.setDisabled(True)

    def view_material(self):
       self.material = material.Material()
       self.mdi.addSubWindow(self.material)
       self.material.show()


material_class, material_base_class = loadUiType(getcwd() + '/ui/material.ui')
class Material(QMainWindow, material_class):
   def __init__(self, *args):
       super(Material, self).__init__()
       self.setupUi(self)

app = QApplication(sys.argv)
main = form.main_window.MainWindow()
sys.exit(app.exec_())

Answer 1

Here is the solution, I'll write it as best as I can

self.material = material.Material() #создаем экземпляр класса окна которое будет внутри MDI
self.sub_material = QMdiSubWindow() #Создаем пустое под окно MDI
self.sub_material.setWidget(self.material) #Заполняем пустое окно нашим классом
self.mdi.addSubWindow(self.sub_material) #Добавляем окно к самой MDI области
self.sub_material.resize(self.material.size()) #Редактируем размер MDI под окна, взяв размеры из созданного в дизайнере класса
self.sub_material.show() #Отображаем под окно