Calling QMainWindow From Second QDialog

Question

My PyQt application starts with Login screen. If password OK, a module-screen (with icons) appears. When user click some button, a QMainWindow will appears. But I can't do this because of qmainwindow object has no attribute '_exec' error. This is my code:

from PyQt4.QtGui import *
from PyQt4.QtCore import *

class Main(QMainWindow):
    def __init__(self, parent=None):
        super(Main, self).__init__(parent)
        ...
        ...

class Login(QDialog):
    def __init__(self, parent=None):
        super(Login, self).__init__(parent)
        ...
        ...

uyg=QApplication(sys.argv)

class icons(QDialog):
    def __init__(self, parent=None):
        super(icons, self).__init__(parent)
        ...
        self.buton = QPushButton()
        self.buton.pressed.connect(self.open)
        ...
    def open(self):
        dialogmain = Main()
        dialogmain._exec() #or dialogmain.show() ???
        self.accept()
        self.close()
        uyg.exec_()    

if Login().exec_() == QDialog.Accepted:
    dialog = icons()
    dialog.exec_()
else:
    uyg.quit()

What am I doing wrong? Thank you.

Answer 1

Lately i have done the similar work:I have a loging window and a main window ,and I used something like a FSM to switch between the loging and main window. Let's say we have 3 state:loging,main,quit.

STATE_LOGING = 0
STATE_MAIN = 1
STATE_QUIT = 2
STATE_DESTROY = 3    #this is a flag

class CState():
    sigSwitchState = pyqtSignal(int)
    def __init__(self):
        super(CState,self).__init__()
    
    def start(self):
        pass

    def sendQuit(self,nextstate):
        self.sigSwitch.emit(nextstate)

class CLoginState(CState):
    def __init__(self):
        super(CLoginState,self).__init__()

    def start(self):
        w = Loging()
        w.show()

    def whenPasswdOk(self):
        self.sendQuit(STATE_MAIN)

class CMainState(CState):
    def __init__(self):
        super(CMainState,self).__init__()
 
    def start(self):
        w = MainWindow()
        w.show()

    def whenMainWindowQuit(self):
        self.sendQuit(STATE_QUIT)

class CQuitState(CState):
    def __init__(self):
        super(CQuitState,self).__init__()

    def start(self):
        #do some clean stuff...
        pass
    def whenCleanDone(self):
        self.sendQuit(STATE_DESTROY)

class CMainApp():
    def __init__(self):
        self.app = QApplication(sys.argv)
        
    def __CreateState(state):
        if state == STATE_LOGING:
            s = CLoginState()
        if state == STATE_MAIN:
            s = CMainState()
        #... same as other state
        s.sigSwitchState.connect(self.procNextState)

   def procNextState(self,state):
       if state == STATE_DESTROY:
            QApplication().exit()

       s = self.__CreateState(state)
       s.start()
    
    def run(self):
        self.procNextState(STATE_LOGING)
        sys.exit(self.app.exec_())

if __name__ == "__main__":
    app = CMainApp()
    app.run()