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    Qt World Summit: Early-Bird Tickets

    Login window

    General and Desktop
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    • N
      ninio last edited by

      Hi, I'm trying to do a login window wich must to be closed and open the main window. When user achieves the login I do:

      @MainWindow mw;
      mw.show();@

      But the new window does not appear. What am I doing wrong or what do I have to do?.

      Thank you.

      1 Reply Last reply Reply Quote 0
      • P
        pushpendrak last edited by

        if you are creating window inside some function then it is wrong as the window get created and shown, immediately it will get destroyed as the "mw" scope is inside that function only.
        @
        int main(...)
        {
        QApplication app(...);
        Mainwindow mw;
        mw.show();
        //wrong method
        return 0;
        // correct method
        return app.exec();
        /* here it will keep running as a thread so you will able to view the mainwindow, if return is some 0,1 etc. then it will break and you will not able to see the windows created, as it got destroyed out side the scope*/
        }@

        PushpendraK

        1 Reply Last reply Reply Quote 0
        • M
          Mario84 last edited by

          There's two simple ways:

          1. Open your Login-Widget in main() before showing MainWindow (both from main())
          2. Show MainWindow and Open the Login-Widget from inside MainWindows constructor. (MainWindow itself will not be displayed until the constructor is finished)
          1 Reply Last reply Reply Quote 0
          • N
            ninio last edited by

            Finally I did:

            @MainWindow* mw = new MainWindow;
            this->close();
            mw->show();@

            Creating the window at the heap works. Thank you for the answers.

            1 Reply Last reply Reply Quote 0
            • R
              ReshmaS last edited by

              @ninio:could you post your code here,. it might be of some help to me. Thanks.

              Reshma

              1 Reply Last reply Reply Quote 0
              • Jeroentjehome
                Jeroentjehome last edited by

                Hi Ninio,
                Though it might work like that you have a potential memory leak at hand. When the new MainWindow is created it will give you the pointer to it so you can reverence it later on in your program. If the new operator is inside your logInWindow the pointer will be destroyed when the LogInWindow function is closed making the MainWindow unreachable by your code! The mw pointer should then be a public MainWindow pointer.
                When the pointer is not accessable anymore the memory can't be released until the program shutdown. When a new logIn Window is created a complete new mainwindow will appear.
                Might be better to use a parent pointer in the LogInWindow to alter the mainWindow show/hide options.
                Greetz

                Greetz, Jeroen

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                • A
                  andre last edited by

                  Actually, the window will be accessible via the QApplication object. You are right in principle, but things are not as bad as they seem :-)

                  1 Reply Last reply Reply Quote 0
                  • Jeroentjehome
                    Jeroentjehome last edited by

                    Ah, oke, learned something new there. Nice, but still it is bad pratice to create a new object and don't keep the pointer at hand ;-)

                    Greetz, Jeroen

                    1 Reply Last reply Reply Quote 0
                    • I
                      issam last edited by

                      Hi all,
                      I tried to resolve the problem by writing a code example: (Connecting to a PostgreSQL data base)

                      create a login window

                      create a data base connection

                      show the login window

                      enter the username and the passwd (repeat until the login is accepted or the operation is canceled)

                      login succeeded ==> create and show the main window

                      @
                      int main(int argc, char *argv[])
                      {
                      QApplication app(argc, argv);

                      LoginWindow Lwindow;

                      /* accepted = 1; rejected = 0; */
                      int result;
                      bool pass = false;
                      int response;

                      QSqlDatabase Dbase;
                      Dbase = QSqlDatabase::addDatabase("QPSQL");
                      Dbase.setHostName("localhost");
                      Dbase.setDatabaseName("database_name");

                      while(!pass)
                      {
                      Lwindow.exec();
                      result = Lwindow.result();
                      if(result == 0)
                      {
                      pass = true;
                      Lwindow.done(0);
                      return 0;
                      }
                      else
                      {
                      QString user = Lwindow.getUser();
                      QString password = Lwindow.getPassword();
                      Dbase.setUserName(user);
                      Dbase.setPassword(password);
                      pass = Dbase.open();

                      /* if(m_dbase.lastError().isValid()) */
                      if(!pass)
                      {
                      response = QMessageBox::critical(NULL, "Data Base Access Problem",Dbase.lastError().text(),QMessageBox::Cancel|QMessageBox::Retry);
                      if(response == QMessageBox::Cancel)
                      {
                      pass = true;
                      return 0;
                      }
                      }
                      }
                      }

                      MainWindow Mwindow(Dbase);
                      Mwindow.setGeometry(100,100,500,600);
                      Mwindow.show();
                      return app.exec();
                      }

                      @

                      http://www.iissam.com/

                      1 Reply Last reply Reply Quote 0
                      • A
                        andre last edited by

                        [quote author="issam" date="1348049464"]Hi all,
                        I tried to resolve the problem by writing a code example like this :
                        [/quote]

                        Nice. And what was the result of that attempt? Did it work? If it did: congrats. If it did not: what failed exactly? What did you expect?

                        1 Reply Last reply Reply Quote 0
                        • Jeroentjehome
                          Jeroentjehome last edited by

                          If you ask me it should work just fine. Maybe a bit of comments to add, but looks fine to me. Did it work??

                          Greetz, Jeroen

                          1 Reply Last reply Reply Quote 0
                          • I
                            issam last edited by

                            It works well ! ;)

                            "download...":http://www.iissam.com/dbases/index.html

                            http://www.iissam.com/

                            1 Reply Last reply Reply Quote 0
                            • A
                              andre last edited by

                              In that case, please go and edit your first post in this topic to add a [Solved] tag to the title.

                              1 Reply Last reply Reply Quote 0
                              • M
                                Macro last edited by

                                [quote author="issam" date="1348128467"]
                                It works well ! ;)

                                "download...":http://www.iissam.com/dbases/index.html
                                [/quote]

                                Thank you....

                                1 Reply Last reply Reply Quote 0
                                • Y
                                  yupifourbi last edited by

                                  Dear issam,

                                  Where is the Lwindow definition? Do you separate into lwindow.cpp and lwindow.h?

                                  Thanks in advance.

                                  1 Reply Last reply Reply Quote 0
                                  • I
                                    issam last edited by

                                    Yes in loginwindow.h and LoginWindow.cpp :)

                                    http://www.iissam.com/

                                    1 Reply Last reply Reply Quote 0
                                    • S
                                      sinant last edited by

                                      Can you reupload the source code :) ?

                                      1 Reply Last reply Reply Quote 0
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