twice execution of click on pushbutton?

[rambo83]

Hello,

I'm very confused about the fact, that if I click (left mouse button) on a pushbutton, then the function connected via SLOT to the SIGNAL of pushbuttons is executed twice. Why? I want it to be executed only one time! How to avoid this behaviour?

I have created my GUI Framework by means of Qt Designer 4.5.1 and then connect the SLOTs automatically by the command "QMetaObject::connectSlotsByName(this);"

Here is the part of cpp code:

#include <iostream>
#include <time.h>
 
#include <QtUiTools>
#include <QtGui>
 
#include "mainframe.h"
#include "Vertex.h"
#include "graphicscene.h"
 
using namespace std;
 
mainFrame::mainFrame(QWidget *parent)
    : QMainWindow(parent)
{
	ui.setupUi(this);
 
	ui_pushButton_START =  qFindChild<QPushButton*>(this, "pushButton_START");
	ui_pushButton_Select = qFindChild<QPushButton*>(this, "pushButton_Select");
	ui_pushButton_Recombine = qFindChild<QPushButton*>(this, "pushButton_Recombine");
 
/*
	connect(ui_pushButton_START, SIGNAL(clicked()), this, SLOT(on_pushButton_Recombine_clicked()));
	connect(ui_pushButton_Select, SIGNAL(clicked()), this, SLOT(on_pushButton_Select_clicked()));
	connect(ui_pushButton_Recombine, SIGNAL(clicked()), this, SLOT(on_pushButton_Recombine_clicked()));
*/
 
	QMetaObject::connectSlotsByName(this);

#include <iostream>
#include <time.h>

#include <QtUiTools>
#include <QtGui>

#include "mainframe.h"
#include "Vertex.h"
#include "graphicscene.h"

using namespace std;

mainFrame::mainFrame(QWidget *parent)
    : QMainWindow(parent)
{
	ui.setupUi(this);

	ui_pushButton_START =  qFindChild<QPushButton*>(this, "pushButton_START");
	ui_pushButton_Select = qFindChild<QPushButton*>(this, "pushButton_Select");
	ui_pushButton_Recombine = qFindChild<QPushButton*>(this, "pushButton_Recombine");

/*
	connect(ui_pushButton_START, SIGNAL(clicked()), this, SLOT(on_pushButton_Recombine_clicked()));
	connect(ui_pushButton_Select, SIGNAL(clicked()), this, SLOT(on_pushButton_Select_clicked()));
	connect(ui_pushButton_Recombine, SIGNAL(clicked()), this, SLOT(on_pushButton_Recombine_clicked()));
*/

	QMetaObject::connectSlotsByName(this);

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and here a part of header file:

class mainFrame : public QMainWindow
{
    Q_OBJECT
 
public:
    mainFrame(QWidget *parent = 0);
    ~mainFrame();
 
 
 
// here the slots are declared, which are kind of sink for connected objects
private slots:
     void on_pushButton_Quit_clicked();
     void updateParameters();
     void on_pushButton_START_clicked();
     void on_pushButton_Recombine_clicked();
     void on_pushButton_Select_clicked();

class mainFrame : public QMainWindow
{
    Q_OBJECT

public:
    mainFrame(QWidget *parent = 0);
    ~mainFrame();



// here the slots are declared, which are kind of sink for connected objects
private slots:
     void on_pushButton_Quit_clicked();
     void updateParameters();
     void on_pushButton_START_clicked();
     void on_pushButton_Recombine_clicked();
     void on_pushButton_Select_clicked();

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Help me please to avoid this failure function. Thank you.

best regards,

Vitali

[yogeshgokul]

Please comment this line and see the results.

QMetaObject::connectSlotsByName(this);

QMetaObject::connectSlotsByName(this);

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[Goldmmbr]

i am guessing it is because of:

ui_pushButton_START =  qFindChild<QPushButton*>(this, "pushButton_START");
ui_pushButton_Select = qFindChild<QPushButton*>(this, "pushButton_Select");
ui_pushButton_Recombine = qFindChild<QPushButton*>(this, "pushButton_Recombine");

ui_pushButton_START =  qFindChild<QPushButton*>(this, "pushButton_START");
ui_pushButton_Select = qFindChild<QPushButton*>(this, "pushButton_Select");
ui_pushButton_Recombine = qFindChild<QPushButton*>(this, "pushButton_Recombine");

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i think it's causing connectSlotsByName to connect the signal/slot for each button twice because you have an aditional pointer ...
i may be wrong though...

[spirit]

notice: QMetaObject::connectSlotsByName(this); is also used in generated ui_classname.h file.

[rambo83]

You are right, now it works! But why? If I don't connect the SLOTs and SIGNALs automatically or manually, the click on button should not call the corresponding function at all, but it does now. Why?

[yogeshgokul]

You are right, now it works! But why? If I don't connect the SLOTs and SIGNALs automatically or manually, the click on button should not call the corresponding function at all, but it does now. Why?

Because you named them(slots) like that.
If you have a QPushButton named btn. And you created a slot named on_btn_clicked().
It will automatically get connected.
QT ROCKS

[spirit]

because of this "notice: QMetaObject::connectSlotsByName(this); is also used in generated ui_classname.h file."
read this QMetaObject::connectSlotsByName.

[squidge]

You are right, now it works! But why? If I don't connect the SLOTs and SIGNALs automatically or manually, the click on button should not call the corresponding function at all, but it does now. Why?

setupUi() calls connectSlotsByName. You are then calling it yourself too, thus you get two function call per click

[rambo83]

Thank you very much for the explanations. They were very helpful.