有关SIGNAL / SLOT qt4的问题

Question

I have created a GUI which involves selection of topics from one ComboBox ( evaluation_box ) leading to load all the topics related to that particular topic into another ComboBox ( sequence_combo_box ).

The code used for SIGNAL/SLOT is as follows

  connect(ui_.evaluation_box, SIGNAL(currentIndexChanged(QString)), ui_.sequence_combo_box, SLOT(readSequenceFile(char *,char *,struct dirent *)));   

But, on doing so I get the following error message:

Object::connect: No such slot QComboBox::readSequenceFile(char *,char *,struct dirent *)
Object::connect:  (sender name:   'evaluation_box')
Object::connect:  (receiver name: 'sequence_combo_box')

The header file includes the following:

#ifndef rqt_get_sequence_feeder__GetSequenceFeeder_H
#define rqt_get_sequence_feeder__GetSequenceFeeder_H

#include <rqt_gui_cpp/plugin.h>

#include <ui_get_sequence_feeder.h>
#include <dirent.h>
#include <image_transport/image_transport.h>    
#include <sensor_msgs/Image.h>    
#include <opencv2/core/core.hpp>    
#include <QImage>
#include <QList>
#include <QMutex>
#include <QString>
#include <QSize>
#include <QWidget>
#include <vector>

    namespace rqt_get_sequence_feeder {

    class GetSequenceFeeder
      : public rqt_gui_cpp::Plugin
     {

      Q_OBJECT
        public:
           GetSequenceFeeder();

        protected slots:            
          virtual void onFrameChanged(int);
          virtual void readSequenceFile(char *folder,char *sequence,struct dirent *select);
                                          .
                                          .
                                          .
       protected:    
         Ui::GetSequenceFeederWidget ui_;

     };
    }

And the .cpp is as follows:

using namespace std;
namespace rqt_get_sequence_feeder {

GetSequenceFeeder::GetSequenceFeeder()
  : rqt_gui_cpp::Plugin()
  , widget_(0)
{
  setObjectName("GetSequenceFeeder");
}


void GetSequenceFeeder::initPlugin(qt_gui_cpp::PluginContext& context)
{
    connect(ui_.evaluation_box, SIGNAL(currentIndexChanged(QString)),ui_.sequence_combo_box, SLOT(readSequenceFile(char *,char *,struct dirent *)));   
                                      .
                                      .
                                      .
}

void GetSequenceFeeder::readSequenceFile(char *folder ,char *sequenceFile,struct dirent *select)
{
                                     .
                                     .
                                     .
}

I have the function readSequenceFile(char *folder,char *sequence,struct dirent *select); declared in the header file as protected slots: I also tried declaring it as public slot: , did not work. I dont understand what am I doing wrong.

Answer 1

According to your error message , your ui_.sequence_combo_box is a QComboBox , and obviously a QComboBox doesn't have a slot function named readSequenceFile .
ui_.sequence_combo_box should be a class inherit QComboBox