QWidget not response on ComboBox action



  • Hi, I am new to Qt. I encountered a problem related to QWidget. I setup a QWidget, which has a ComboBox selector. My goal is to use this selector to control some behavior in the main app. I initiated the QWidget in the main ui, but when I change the currentText of the ComboBox, it seems that it does nothing at all. Below is my code:

    surfaceproperty.h:

    namespace Ui {
    class SurfaceProperty;
    }
    
    class SurfaceProperty : public QWidget
    {
        Q_OBJECT
    
    public:
        explicit SurfaceProperty(QWidget *parent = 0);
        ~SurfaceProperty();
    
    public slots:
        void on_selectorSurfaceColormap_currentTextChanged(const QString &arg1);
    
    public:
        Ui::SurfaceProperty *uisp;
    };
    

    surfaceproperty.cpp:

    #include "surfaceproperty.h"
    #include "ui_surfaceProperty.h"
    
    SurfaceProperty::SurfaceProperty(QWidget *parent) :
        QWidget(parent),
        uisp(new Ui::SurfaceProperty)
    {
        uisp->setupUi(this);
    }
    
    SurfaceProperty::~SurfaceProperty()
    {
        delete uisp;
    }
    
    void SurfaceProperty::on_selectorSurfaceColormap_currentTextChanged(const QString &arg1)
    {
               qInfo() << arg1;
    }
    

    Part of main app here:

        QWidget *t = new QWidget;
        uif->uisp->setupUi(t);
        t->show();
        t->setWindowTitle("Surface Properties");
        t->setAttribute(Qt::WA_QuitOnClose, false);
        uif->uisp->selectorSurfaceColormap->setCurrentText("test");
    

    where uif is a SurfaceProperty* I defined here in the main app.

    I did not post my ui file here.

    Basically, I expect that when this part of the main app is called, a widget window appears, and when the ComboBox's currentText is changed, I can get a qInfo() output at the cmd (I build it under Linux). But I only get a widget window when this part is called. I did not see the qInfo() output at all, meaning the ComboBox part is not functional at all.

    Could anyone indicate what is the problem? Did I miss some signal & slot thing?

    Thank you very much!


  • Qt Champions 2018

    Please do not use the auto-connect feature but connect the signals/slots by your own. Maybe you've a type on the member name (selectorSurfaceColormap) so the auto-connect feature can not find the slot.



  • @Christian-Ehrlicher Hi, Christian, thanks for the reply but I am a little confused. Why the auto-connect feature is not encouraged? Is this true for all windows or only qwidget? I have many auto-connects in the main app, they all work very well. I also did not quite get it on this line: "...you've a type on the member name". Could you indicate? Thanks a lot!


  • Qt Champions 2018

    I said 'Maybe you've a typo...'
    The problem with auto-connect is that you can not be sure if it is really connected (e.g. when there is a typo somewhere in the functions signature or the ui element name) and it easily breaks (e.g. when renaming an ui element).