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  4. [Solved] How to access progressBar from a QWizardPage subclass
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[Solved] How to access progressBar from a QWizardPage subclass

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  • ? Offline
    ? Offline
    A Former User
    wrote on last edited by
    #4

    I've been trying to solve this, one of the ideas that occurred to me was the following:

    1 - Create a static function in my QWizard subclass:

    @void MyQWizard::updateProgressBar(const int value) {

    ui->progressBar->setValue(value);
    

    }@

    ...remember that the only place where I can access the progressBar is from the QWizard subclass.

    2 -Update the progressBar from my QWizardPage subclass:

    @MyQWizard::updateProgressBar(value);@

    ...but it doesn't work. QtCreator give me an error, it said that I've committed a violation using "ui->progressBar->setValue(value);" from a static function.

    ...so I'm stuck again!!!

    Thanks for help.

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    • C Offline
      C Offline
      Chris H
      wrote on last edited by
      #5

      What error do you get, exactly, when you try to call
      @ui->progressBar->setValue(value);@
      from a member function (you certainly can't access it from a static function if it's a member variable!).

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      • ? Offline
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        A Former User
        wrote on last edited by
        #6

        Here is the error that I got when I try to call:

        @
        ui->progressBar->setValue(value);
        @

        ...from a static function.

        The error output:

        In static member function 'static void MyQWizard::updateProgressBar(int)':
        error: invalid use of member 'MyQWizard::ui' in static member function

        ...This error points to the line 42 of my code which have the follow declaration:

        @
        private:
        Ui::CreateRepoWizard *ui;
        @

        ...included "private:" for clarity.

        Thanks for help.

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        • C Offline
          C Offline
          Chris H
          wrote on last edited by
          #7

          You cannot access a member variable from a static function: what error do you get when you try to do that from a member function?

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          • ? Offline
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            A Former User
            wrote on last edited by
            #8

            In the example that I wrote above you can see that the function:

            myqwizard.cpp:
            @
            MyQWizard::MyQWizard(QWidget *parent) : QWizard(parent), ui(new Ui::CreateRepoWizard) {

            ...

            }

            ...

            void MyQWizard::updateProgressBar(const int value) {

              ui->progressBar->setValue(value);
            

            }

            ...

            @

            ...is a member of MyQWizard class and as I said, it was declared as a static function:

            myqwizard.h:
            @
            public:
            static void updateProgressBar(const int value);
            @

            I need this function be static, to be able to access it from progressPage(a QWizardPage subclass) without creating a new object of MyQWizard :

            progresspage.cpp:
            @

            #include <myqwizard.h>

            ProgressPage::ProgressPage(QWidget *parent) : QWizardPage(parent) {

            ...

            }

            ...

            MyQWizard::updateProgressBar(value);

            ...
            @

            Creating this member function as non-static will allow me to update the progressBar without problems, but it implies to create a new object of MyQWizard too, which doesn't have any sense in this scenario. Because I will be using a new instance of MyQWizard rather than the current, therefore I will be updating a different progressBar, that it's not the one that the wizard window shows.

            Anyway thanks for the correction.

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            • C Offline
              C Offline
              Chris H
              wrote on last edited by
              #9

              There are a couple approaches you can use here: the first is to emit a signal in ProgressPage that indicates that it would like the progress bar updated, and connect to that in MyQWizard to do the update. A second approach is to get a pointer to MyQWizard from within ProgressPage (is MyQWizard a parent widget, perhaps?). I'd lean towards to first solution for encapsulation reasons, but either will work. Fundamentally, though, you must have an object to operate on: that's why you can't use a static function.

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              • ? Offline
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                A Former User
                wrote on last edited by
                #10

                As I said, thanks for the correction. I already understood that I can't use a static function. My next step will be try your suggestion, thanks again.

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                • ? Offline
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                  A Former User
                  wrote on last edited by
                  #11

                  Got it!!!

                  l used the signal-slot approach as you suggested and it worked at the first try. It was so easy that I feel ashamed right now, but well, I guess it's a matter of experience.

                  Thanks for your continuous help and support, Chris H.

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                  • A Offline
                    A Offline
                    astodolski
                    wrote on last edited by
                    #12

                    What did you use for the signal to emit? Value changed is a signal that is emitted from the progress bar. It looks like from your posting that you wanted to call MyQWizard::updateProgressBar(value); and you said you used a signal-slot solution. I was hoping to see what you used as a solution scheme.

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                      A Former User
                      wrote on last edited by
                      #13

                      I don't have access to the original code right now, so I made an example for you to have an idea how I've solved this.

                      Note that I've promoted the object "ui->progressBarPage" to "ProgressPage".

                      Here is the code:

                      mywizard.h:

                      @#ifndef MYWIZARD_H
                      #define MYWIZARD_H

                      #include <QWizard>

                      namespace Ui {

                      class MyWizard;
                      

                      }

                      class MyWizard : public QWizard
                      {

                      Q_OBJECT
                      

                      public:

                      explicit MyWizard(QWidget *parent = 0);
                      
                      ~MyWizard();
                      

                      public slots:

                      void updateProgressBar(const int value);
                      

                      private:

                      Ui::MyWizard *ui;
                      

                      };

                      #endif // MYWIZARD_H@

                      mywizard.cpp:

                      @#include "mywizard.h"
                      #include "ui_mywizard.h"

                      MyWizard::MyWizard(QWidget *parent) : QWizard(parent), ui(new Ui::MyWizard)
                      {

                      ui->setupUi(this);
                      
                      ui->progressBar->reset();
                      
                      connect(ui->progressBarPage, SIGNAL(updateProgressValue(int)), this, SLOT(updateProgressBar(int)));
                      

                      }// Constructor

                      MyWizard::~MyWizard()
                      {

                      delete ui;
                      

                      }// Destructor

                      void MyWizard::updateProgressBar(const int value)
                      {

                      ui->progressBar->setValue(value);
                      

                      }// Update ProgressBar@

                      progresspage.h:

                      @#ifndef PROGRESSPAGE_H
                      #define PROGRESSPAGE_H

                      #include <QWizardPage>
                      #include <QTimer>

                      class ProgressPage : public QWizardPage
                      {

                      Q_OBJECT
                      

                      public:

                      explicit ProgressPage(QWidget *parent = 0);
                      
                      void initializePage();
                      

                      signals:

                      void updateProgressValue(const int value);
                      

                      private slots:

                      void updateValue();
                      

                      private:

                      QTimer *timer;
                      
                      int count;
                      

                      };

                      #endif // PROGRESSPAGE_H@

                      progresspage.cpp:

                      @#include "progresspage.h"

                      ProgressPage::ProgressPage(QWidget *parent) : QWizardPage(parent)
                      {

                      timer = new QTimer(this);
                      
                      count = 0;
                      
                      connect(timer, SIGNAL(timeout()), this, SLOT(updateValue()));
                      

                      }// Constructor

                      void ProgressPage::initializePage() {

                      timer->start(100);
                      

                      }// initializePage

                      void ProgressPage::updateValue() {

                      if(count == 100) {
                      
                          timer->stop();
                      
                          return;
                      
                      }// if
                      
                      count++;
                      
                      emit updateProgressValue(count);
                      

                      }// updateValue@

                      Hope this can help you.

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                      • A Offline
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                        astodolski
                        wrote on last edited by
                        #14

                        Absolutely helps. Thanks very much.

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                        • ? Offline
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                          A Former User
                          wrote on last edited by
                          #15

                          Glad to know it.

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