Skip to content
  • Categories
  • Recent
  • Tags
  • Popular
  • Users
  • Groups
  • Search
  • Get Qt Extensions
  • Unsolved
Collapse
Brand Logo
  1. Home
  2. Qt Development
  3. General and Desktop
  4. QStackedWidget: How to check if the next widget should be shown
Forum Updated to NodeBB v4.3 + New Features

QStackedWidget: How to check if the next widget should be shown

Scheduled Pinned Locked Moved Solved General and Desktop
qstackedwidgetqstackedwidgets
25 Posts 4 Posters 4.1k Views 1 Watching
  • Oldest to Newest
  • Newest to Oldest
  • Most Votes
Reply
  • Reply as topic
Log in to reply
This topic has been deleted. Only users with topic management privileges can see it.
  • H hobbyProgrammer
    21 Nov 2019, 10:07

    @JonB Oh I'm sorry, it should happen on a pushbutton (when it's pressed, it checks if the login was good)

    So like this:

    bool LoginWidget::loginSuccesfull()
    {
        QString username = ui->lineEdit_2->text();
        QString password = ui->lineEdit->text();
    
        if(username == "Test" && password == "Test123")
        {
            return true;
        }
        else
        {
            return false;
        }
    }
    
    void LoginWidget::on_pushButton_clicked()
    {
        loginSuccesfull();
    }
    

    but how do I check the value of loginSuccesfull() in the mainwindow?

    J Online
    J Online
    JonB
    wrote on 21 Nov 2019, 10:17 last edited by JonB
    #4

    @hobbyProgrammer
    There is no point invoking a function from on_pushButton_clicked() which just returns true or false without acting on the return result.

    There are many ways to achieve what you want. I'll just say that it would be easier if you chose to make the login page a modal dialog instead of one of the stacked widgets. That's a different interface, I don't know how you feel about that.

    If you want to keep the login in stacked widget as now: Probably, stop loginSuccessfull() from being a function returning a boolean. Instead, in the false case have it show the user an error message. In the true case, one of:

    • Have it switch back to some other window by calling QStackedWidget::setCurrentIndex(0) (it will have to have access to ui->stackedWidget).
    • Have it raise a signal to indicate successful logon, and the main window will have a slot for that so that the ui->stackedWidget->setCurrentIndex(0) can be done in the main window.

    Ah, I see at present there is only one stacked widget, the login one, so the first alternative may not make sense. If you want your main window code to know about the login result, use the signal/slot mechanism.

    H 1 Reply Last reply 21 Nov 2019, 10:21
    2
    • J JonB
      21 Nov 2019, 10:17

      @hobbyProgrammer
      There is no point invoking a function from on_pushButton_clicked() which just returns true or false without acting on the return result.

      There are many ways to achieve what you want. I'll just say that it would be easier if you chose to make the login page a modal dialog instead of one of the stacked widgets. That's a different interface, I don't know how you feel about that.

      If you want to keep the login in stacked widget as now: Probably, stop loginSuccessfull() from being a function returning a boolean. Instead, in the false case have it show the user an error message. In the true case, one of:

      • Have it switch back to some other window by calling QStackedWidget::setCurrentIndex(0) (it will have to have access to ui->stackedWidget).
      • Have it raise a signal to indicate successful logon, and the main window will have a slot for that so that the ui->stackedWidget->setCurrentIndex(0) can be done in the main window.

      Ah, I see at present there is only one stacked widget, the login one, so the first alternative may not make sense. If you want your main window code to know about the login result, use the signal/slot mechanism.

      H Offline
      H Offline
      hobbyProgrammer
      wrote on 21 Nov 2019, 10:21 last edited by
      #5

      @JonB alright, so I should include the mainWindow.ui file aswell instead of only the loginWidget.ui?

      J 1 Reply Last reply 21 Nov 2019, 10:31
      0
      • H hobbyProgrammer
        21 Nov 2019, 10:21

        @JonB alright, so I should include the mainWindow.ui file aswell instead of only the loginWidget.ui?

        J Online
        J Online
        JonB
        wrote on 21 Nov 2019, 10:31 last edited by JonB
        #6

        @hobbyProgrammer
        No, for your case I would suggest LoginWidget::loginSuccesfull() on success should raise a signal, and MainWindow should place a slot on that signal to receive it.

        I'm sorry but I don't have time to write this all out for you, maybe someone else will. Have you read https://doc.qt.io/qt-5/signalsandslots.html, which is the core of how Qt uses signals & slots?

        H 2 Replies Last reply 21 Nov 2019, 10:32
        0
        • J JonB
          21 Nov 2019, 10:31

          @hobbyProgrammer
          No, for your case I would suggest LoginWidget::loginSuccesfull() on success should raise a signal, and MainWindow should place a slot on that signal to receive it.

          I'm sorry but I don't have time to write this all out for you, maybe someone else will. Have you read https://doc.qt.io/qt-5/signalsandslots.html, which is the core of how Qt uses signals & slots?

          H Offline
          H Offline
          hobbyProgrammer
          wrote on 21 Nov 2019, 10:32 last edited by
          #7

          @JonB Thanks. That's very helpful!

          1 Reply Last reply
          0
          • J JonB
            21 Nov 2019, 10:31

            @hobbyProgrammer
            No, for your case I would suggest LoginWidget::loginSuccesfull() on success should raise a signal, and MainWindow should place a slot on that signal to receive it.

            I'm sorry but I don't have time to write this all out for you, maybe someone else will. Have you read https://doc.qt.io/qt-5/signalsandslots.html, which is the core of how Qt uses signals & slots?

            H Offline
            H Offline
            hobbyProgrammer
            wrote on 21 Nov 2019, 10:44 last edited by hobbyProgrammer
            #8

            @JonB so should it be something like this?

                connect(ui->stackedWidget->indexOf(0), SIGNAL(loginSuccesfull()), this, SLOT(showApp()));
            

            I might be close, but it's not working yet. Do you see what I am doing wrong?

            I also tried this:

                Login *login = ui->stackedWidget->indexOf(0);
                
                connect(login, SIGNAL(loginSuccesfull()), this, SLOT(showApp()));
            
            J 1 Reply Last reply 21 Nov 2019, 11:06
            0
            • H hobbyProgrammer
              21 Nov 2019, 10:44

              @JonB so should it be something like this?

                  connect(ui->stackedWidget->indexOf(0), SIGNAL(loginSuccesfull()), this, SLOT(showApp()));
              

              I might be close, but it's not working yet. Do you see what I am doing wrong?

              I also tried this:

                  Login *login = ui->stackedWidget->indexOf(0);
                  
                  connect(login, SIGNAL(loginSuccesfull()), this, SLOT(showApp()));
              
              J Online
              J Online
              JonB
              wrote on 21 Nov 2019, 11:06 last edited by JonB
              #9

              @hobbyProgrammer
              Whatever else might be wrong, QStackedWidget::indexOf() is totally the wrong way round. As I wrote earlier, you will need to use QStackedWidget::widget(), and if you need a reference to it being a LoginWidget to access members of that class you will want something like:

              loginWidget = qobject_cast<LoginWidget*>(ui->stackedWidget.widget(0))
              
              H 1 Reply Last reply 21 Nov 2019, 11:36
              1
              • J JonB
                21 Nov 2019, 11:06

                @hobbyProgrammer
                Whatever else might be wrong, QStackedWidget::indexOf() is totally the wrong way round. As I wrote earlier, you will need to use QStackedWidget::widget(), and if you need a reference to it being a LoginWidget to access members of that class you will want something like:

                loginWidget = qobject_cast<LoginWidget*>(ui->stackedWidget.widget(0))
                
                H Offline
                H Offline
                hobbyProgrammer
                wrote on 21 Nov 2019, 11:36 last edited by
                #10

                @JonB thank you.

                    LoginWidget *login = qobject_cast<LoginWidget*>(ui->stackedWidget->widget(0));
                
                    connect(login, SIGNAL(loginSuccesfull()), this, SLOT(showApp()));
                

                I currently get these errors (as loginSuccesfull is a public bool method):

                QObject::connect: No such signal LoginWidget::loginSuccesfull() in ..\stackedLogin\mainwindow.cpp:14
                QObject::connect:  (sender name:   'page')
                QObject::connect:  (receiver name: 'MainWindow')
                

                whenever I change loginSuccesfull() to a signal instead of public bool I get these errors:

                LNK2005:"public: bool _thiscall LoginWidget::loginSuccesfull(void)......" and LNK1169: one or more multiply defined symbols found

                J J 2 Replies Last reply 21 Nov 2019, 11:38
                0
                • H hobbyProgrammer
                  21 Nov 2019, 11:36

                  @JonB thank you.

                      LoginWidget *login = qobject_cast<LoginWidget*>(ui->stackedWidget->widget(0));
                  
                      connect(login, SIGNAL(loginSuccesfull()), this, SLOT(showApp()));
                  

                  I currently get these errors (as loginSuccesfull is a public bool method):

                  QObject::connect: No such signal LoginWidget::loginSuccesfull() in ..\stackedLogin\mainwindow.cpp:14
                  QObject::connect:  (sender name:   'page')
                  QObject::connect:  (receiver name: 'MainWindow')
                  

                  whenever I change loginSuccesfull() to a signal instead of public bool I get these errors:

                  LNK2005:"public: bool _thiscall LoginWidget::loginSuccesfull(void)......" and LNK1169: one or more multiply defined symbols found

                  J Online
                  J Online
                  J.Hilk
                  Moderators
                  wrote on 21 Nov 2019, 11:38 last edited by
                  #11

                  @hobbyProgrammer

                  A Signal must not have a definition, only a declaration.

                  The definition is made automatically in generated code by moc


                  Be aware of the Qt Code of Conduct, when posting : https://forum.qt.io/topic/113070/qt-code-of-conduct


                  Q: What's that?
                  A: It's blue light.
                  Q: What does it do?
                  A: It turns blue.

                  H 1 Reply Last reply 21 Nov 2019, 12:33
                  3
                  • H hobbyProgrammer
                    21 Nov 2019, 11:36

                    @JonB thank you.

                        LoginWidget *login = qobject_cast<LoginWidget*>(ui->stackedWidget->widget(0));
                    
                        connect(login, SIGNAL(loginSuccesfull()), this, SLOT(showApp()));
                    

                    I currently get these errors (as loginSuccesfull is a public bool method):

                    QObject::connect: No such signal LoginWidget::loginSuccesfull() in ..\stackedLogin\mainwindow.cpp:14
                    QObject::connect:  (sender name:   'page')
                    QObject::connect:  (receiver name: 'MainWindow')
                    

                    whenever I change loginSuccesfull() to a signal instead of public bool I get these errors:

                    LNK2005:"public: bool _thiscall LoginWidget::loginSuccesfull(void)......" and LNK1169: one or more multiply defined symbols found

                    J Online
                    J Online
                    JonB
                    wrote on 21 Nov 2019, 11:41 last edited by
                    #12

                    @hobbyProgrammer
                    In some shape or form you have not changed over the code to how signals/slots are declared and work in Qt. There are lots of example to read. You will need correct Qt declarations using signals & slots in your header files, and loginSuccesfull() won't be some bool function, it will emit the signal.

                    I will leave others to help you with this, I don't even do Qt in C++.

                    1 Reply Last reply
                    0
                    • J J.Hilk
                      21 Nov 2019, 11:38

                      @hobbyProgrammer

                      A Signal must not have a definition, only a declaration.

                      The definition is made automatically in generated code by moc

                      H Offline
                      H Offline
                      hobbyProgrammer
                      wrote on 21 Nov 2019, 12:33 last edited by
                      #13

                      @J-Hilk alright, but how would I check if the login is correct if there's no function definition?

                      J J 2 Replies Last reply 21 Nov 2019, 12:36
                      0
                      • H hobbyProgrammer
                        21 Nov 2019, 12:33

                        @J-Hilk alright, but how would I check if the login is correct if there's no function definition?

                        J Online
                        J Online
                        J.Hilk
                        Moderators
                        wrote on 21 Nov 2019, 12:36 last edited by J.Hilk
                        #14

                        @hobbyProgrammer

                        the idea would be, that you emit the signal, as soon as your function verifies, that the login was successful !

                        void LoginWidget::on_pushButton_clicked()
                        {
                               QString username = ui->lineEdit_2->text();
                                QString password = ui->lineEdit->text();
                            
                                if(username == "Test" && password == "Test123")
                                {
                                     emit loginSuccessful();
                                }
                        }
                        

                        Be aware of the Qt Code of Conduct, when posting : https://forum.qt.io/topic/113070/qt-code-of-conduct


                        Q: What's that?
                        A: It's blue light.
                        Q: What does it do?
                        A: It turns blue.

                        1 Reply Last reply
                        3
                        • H hobbyProgrammer
                          21 Nov 2019, 12:33

                          @J-Hilk alright, but how would I check if the login is correct if there's no function definition?

                          J Online
                          J Online
                          JonB
                          wrote on 21 Nov 2019, 12:37 last edited by JonB
                          #15

                          @hobbyProgrammer
                          Subject to @J-Hilk suggesting an alternative, as I wrote earlier retain your loginSuccesfull() as the slot for the pushbutton click. Have it emit a signal you define on successful validation of the widgets, the signal is a separate thing from your function which you must define as per the Qt/C++ rules.

                          EDIT OK, @J-Hilk's code is the same thing, it's just that he has defined the pushbutton slot as on_pushButton_clicked() and the signal as logInSuccessful, so there is no longer any (non-signal) function named loginSuccesfull().

                          H 1 Reply Last reply 21 Nov 2019, 12:53
                          0
                          • J JonB
                            21 Nov 2019, 12:37

                            @hobbyProgrammer
                            Subject to @J-Hilk suggesting an alternative, as I wrote earlier retain your loginSuccesfull() as the slot for the pushbutton click. Have it emit a signal you define on successful validation of the widgets, the signal is a separate thing from your function which you must define as per the Qt/C++ rules.

                            EDIT OK, @J-Hilk's code is the same thing, it's just that he has defined the pushbutton slot as on_pushButton_clicked() and the signal as logInSuccessful, so there is no longer any (non-signal) function named loginSuccesfull().

                            H Offline
                            H Offline
                            hobbyProgrammer
                            wrote on 21 Nov 2019, 12:53 last edited by
                            #16

                            @JonB alright, so using that code and these lines:

                                LoginWidget *login = qobject_cast<LoginWidget*>(ui->stackedWidget->widget(0));
                                connect(login, SIGNAL(loginSuccesfull()), this, SLOT(showApp()));
                            

                            should result in showApp to happen anytime the login was succesfull?

                            J 1 Reply Last reply 21 Nov 2019, 13:04
                            0
                            • H hobbyProgrammer
                              21 Nov 2019, 12:53

                              @JonB alright, so using that code and these lines:

                                  LoginWidget *login = qobject_cast<LoginWidget*>(ui->stackedWidget->widget(0));
                                  connect(login, SIGNAL(loginSuccesfull()), this, SLOT(showApp()));
                              

                              should result in showApp to happen anytime the login was succesfull?

                              J Online
                              J Online
                              JonB
                              wrote on 21 Nov 2019, 13:04 last edited by
                              #17

                              @hobbyProgrammer
                              I'm hoping so! Did you try it?

                              H 1 Reply Last reply 21 Nov 2019, 13:09
                              0
                              • J JonB
                                21 Nov 2019, 13:04

                                @hobbyProgrammer
                                I'm hoping so! Did you try it?

                                H Offline
                                H Offline
                                hobbyProgrammer
                                wrote on 21 Nov 2019, 13:09 last edited by
                                #18

                                @JonB yes and it didn't work. I tried debugging but I can't seem to find what's going wrong. It hits the code where the emit loginSuccessfull() is set, but it doesn't go to the SLOT where it's connected to and it ends in :

                                while (!d->exit.loadAcquire())
                                        processEvents(flags | WaitForMoreEvents | EventLoopExec);
                                
                                J 1 Reply Last reply 21 Nov 2019, 13:13
                                0
                                • H hobbyProgrammer
                                  21 Nov 2019, 13:09

                                  @JonB yes and it didn't work. I tried debugging but I can't seem to find what's going wrong. It hits the code where the emit loginSuccessfull() is set, but it doesn't go to the SLOT where it's connected to and it ends in :

                                  while (!d->exit.loadAcquire())
                                          processEvents(flags | WaitForMoreEvents | EventLoopExec);
                                  
                                  J Online
                                  J Online
                                  jsulm
                                  Lifetime Qt Champion
                                  wrote on 21 Nov 2019, 13:13 last edited by
                                  #19

                                  @hobbyProgrammer Did you make sure

                                  connect(login, SIGNAL(loginSuccesfull()), this, SLOT(showApp()));
                                  

                                  succeeded? And is this "login" the one you're actually showing?

                                  https://forum.qt.io/topic/113070/qt-code-of-conduct

                                  H 1 Reply Last reply 21 Nov 2019, 13:18
                                  1
                                  • J jsulm
                                    21 Nov 2019, 13:13

                                    @hobbyProgrammer Did you make sure

                                    connect(login, SIGNAL(loginSuccesfull()), this, SLOT(showApp()));
                                    

                                    succeeded? And is this "login" the one you're actually showing?

                                    H Offline
                                    H Offline
                                    hobbyProgrammer
                                    wrote on 21 Nov 2019, 13:18 last edited by
                                    #20

                                    @jsulm
                                    it should be since I'm doing this:

                                        LoginWidget *login = qobject_cast<LoginWidget*>(ui->stackedWidget->widget(0));
                                    
                                    J 1 Reply Last reply 21 Nov 2019, 13:19
                                    0
                                    • H hobbyProgrammer
                                      21 Nov 2019, 13:18

                                      @jsulm
                                      it should be since I'm doing this:

                                          LoginWidget *login = qobject_cast<LoginWidget*>(ui->stackedWidget->widget(0));
                                      
                                      J Online
                                      J Online
                                      jsulm
                                      Lifetime Qt Champion
                                      wrote on 21 Nov 2019, 13:19 last edited by
                                      #21

                                      @hobbyProgrammer And connect succeeded?

                                      https://forum.qt.io/topic/113070/qt-code-of-conduct

                                      H 1 Reply Last reply 21 Nov 2019, 13:24
                                      1
                                      • J jsulm
                                        21 Nov 2019, 13:19

                                        @hobbyProgrammer And connect succeeded?

                                        H Offline
                                        H Offline
                                        hobbyProgrammer
                                        wrote on 21 Nov 2019, 13:24 last edited by
                                        #22

                                        @jsulm I'm not sure, but I don't think so.

                                        J 1 Reply Last reply 21 Nov 2019, 13:26
                                        0
                                        • H hobbyProgrammer
                                          21 Nov 2019, 13:24

                                          @jsulm I'm not sure, but I don't think so.

                                          J Online
                                          J Online
                                          jsulm
                                          Lifetime Qt Champion
                                          wrote on 21 Nov 2019, 13:26 last edited by
                                          #23

                                          @hobbyProgrammer said in QStackedWidget: How to check if the next widget should be shown:

                                          but I don't think so

                                          Then it can't work.
                                          Use new Qt5 connect syntax to be sure signal/slot are really connected:

                                          connect(login, &LoginWidget::loginSuccesfull, this, &MainWindow::showApp);
                                          

                                          https://forum.qt.io/topic/113070/qt-code-of-conduct

                                          H 1 Reply Last reply 21 Nov 2019, 13:27
                                          2

                                          13/25

                                          21 Nov 2019, 12:33

                                          • Login

                                          • Login or register to search.
                                          13 out of 25
                                          • First post
                                            13/25
                                            Last post
                                          0
                                          • Categories
                                          • Recent
                                          • Tags
                                          • Popular
                                          • Users
                                          • Groups
                                          • Search
                                          • Get Qt Extensions
                                          • Unsolved